min 3 S min 3 S min 6 3 S min S min

Transcription

1 De Tabellen Tijd Tra Tijd Tra Tijd Trappen Tijd Trappen Tijd Trappen min 3 S min 3 S min 6 3 S min S min A 15 C 10 C 5 C B 20 D 15 E 10 E C 25 E 20 F 15 2 G F 25 G 20 6 I B 40 G 30 H J C 50 H 40 7 J K D 55 I L N E 60 J M K N 5 C B 80 7 L E C M 10 D 15 3 G D E H E 10 C 20 F K F 15 D 25 H L G 20 E 30 3 I N F K B 35 G L 5 D C 40 H N 10 1 F D 45 I H E 50 J 10 D J F 60 8 K 15 F K G L 20 G M H M 25 3 H N I N 30 7 J J N L 5 D K M 10 2 F L 5 B N H M 10 C J D 5 C L C 20 E 10 D M D 25 F 15 F E 30 G 20 2 H 5 D F 35 H 25 6 I 10 3 F G 40 I J I H K L K I L N L J M N K 5 C L 10 E 5 D L 15 1 F G M 20 4 H I M J K N M M N

2 A B C D E F G H I J K L M N TUSSENTIJD IN MINUTEN 0:10 12:00 0:10 3:21 12:00 0:10 1:40 4:50 12:00 0:10 1:10 2:39 5:49 12:00 0:10 0:55 1:58 3:25 6:35 12:00 0:10 0:46 1:30 2:29 3:58 7:06 12:00 0:10 0:41 1:16 2:00 2:59 4:26 7:36 12:00 0:10 0:37 1:07 1:42 2:24 3:21 4:50 8:00 12:00 0:10 0:34 1:00 1:30 2:03 2:45 3:44 5:13 8:22 12:00 0:10 0:32 0:55 1:20 1:48 2:21 3:05 4:03 5:41 8:51 12:00 0:10 0:29 0:50 1:12 1:36 2:04 2:39 3:22 4:20 5:49 8:59 12:00 0:10 0:27 0:46 1:05 1:26 1:50 2:20 2:54 3:37 4:36 6:03 9:13 12:00 0:10 0:26 0:43 1:00 1:19 1:40 2:06 2:35 3:09 3:53 4:50 6:19 9:29 12:00 0:10 0:25 0:40 0:55 1:12 1:31 1:54 2:19 2:48 3:23 4:05 5:04 6:33 9:44 12:00 Diepte N M L K J I H G F E D C B A 3 * * * * * * * * * * * * * * *

3

4 T (minuten) Tabel T T (minuten) 0,69 t min t min ,1294 0,0670 0,0341 0,0172 0,0086 0,0058 0,0043 0,0035 0, ,9854 0,8793 0,6525 0,4105 0,2970 0,2322 0,1906 0, ,2421 0,1294 0,0670 0,0341 0,0172 0,0115 0,0086 0,0069 0, ,9864 0,8834 0,6585 0,4156 0,3010 0,2355 0,1934 0, ,3402 0,1877 0,0987 0,0507 0,0257 0,0172 0,0129 0,0103 0, ,9873 0,8873 0,6644 0,4207 0,3050 0,2389 0,1961 0, ,4257 0,2421 0,1294 0,0670 0,0341 0,0228 0,0172 0,0138 0, ,9882 0,8912 0,6701 0,4257 0,3090 0,2421 0,1989 0, ,5000 0,2929 0,1591 0,0830 0,0424 0,0285 0,0214 0,0172 0, ,9890 0,8949 0,6758 0,4306 0,3130 0,2454 0,2017 0, ,5647 0,3402 0,1877 0,0987 0,0507 0,0341 0,0257 0,0206 0, ,9897 0,8985 0,6814 0,4355 0,3170 0,2487 0,2045 0, ,6211 0,3844 0,2154 0,1142 0,0588 0,0396 0,0299 0,0240 0, ,9904 0,9019 0,6868 0,4404 0,3209 0,2519 0,2072 0, ,6701 0,4257 0,2421 0,1294 0,0670 0,0452 0,0341 0,0273 0, ,9910 0,9053 0,6922 0,4452 0,3248 0,2552 0,2100 0, ,7128 0,4641 0,2680 0,1444 0,0750 0,0507 0,0382 0,0307 0, ,9916 0,9085 0,6975 0,4500 0,3287 0,2584 0,2127 0, ,7500 0,5000 0,2929 0,1591 0,0830 0,0561 0,0424 0,0341 0, ,9922 0,9116 0,7027 0,4547 0,3326 0,2616 0,2154 0, ,7824 0,5335 0,3170 0,1735 0,0909 0,0616 0,0465 0,0374 0, ,9927 0,9146 0,7078 0,4594 0,3364 0,2648 0,2181 0, ,8105 0,5647 0,3402 0,1877 0,0987 0,0670 0,0507 0,0407 0, ,9932 0,9175 0,7128 0,4641 0,3402 0,2680 0,2208 0, ,8351 0,5939 0,3627 0,2017 0,1065 0,0723 0,0548 0,0441 0, ,9937 0,9203 0,7178 0,4687 0,3440 0,2711 0,2235 0, ,8564 0,6211 0,3844 0,2154 0,1142 0,0777 0,0588 0,0474 0, ,9941 0,9231 0,7226 0,4733 0,3478 0,2743 0,2262 0, ,8750 0,6464 0,4054 0,2289 0,1219 0,0830 0,0629 0,0507 0, ,9945 0,9257 0,7274 0,4779 0,3516 0,2774 0,2289 0, ,8912 0,6701 0,4257 0,2421 0,1294 0,0883 0,0670 0,0539 0, ,9948 0,9282 0,7321 0,4824 0,3553 0,2805 0,2316 0, ,9053 0,6922 0,4452 0,2552 0,1370 0,0935 0,0710 0,0572 0, ,9952 0,9307 0,7367 0,4868 0,3590 0,2836 0,2342 0, ,9175 0,7128 0,4641 0,2680 0,1444 0,0987 0,0750 0,0605 0, ,9955 0,9330 0,7412 0,4913 0,3627 0,2867 0,2369 0, ,9282 0,7321 0,4824 0,2805 0,1518 0,1039 0,0790 0,0637 0, ,9958 0,9353 0,7456 0,4956 0,3664 0,2898 0,2395 0, ,9375 0,7500 0,5000 0,2929 0,1591 0,1091 0,0830 0,0670 0, ,9961 0,9375 0,7500 0,5000 0,3700 0,2929 0,2421 0, ,9456 0,7667 0,5170 0,3050 0,1664 0,1142 0,0870 0,0702 0, ,9964 0,9396 0,7543 0,5043 0,3737 0,2959 0,2448 0, ,9526 0,7824 0,5335 0,3170 0,1735 0,1193 0,0909 0,0734 0, ,9966 0,9417 0,7585 0,5086 0,3773 0,2990 0,2474 0, ,9588 0,7969 0,5494 0,3287 0,1807 0,1244 0,0948 0,0766 0, ,9968 0,9437 0,7627 0,5128 0,3809 0,3020 0,2500 0, ,9641 0,8105 0,5647 0,3402 0,1877 0,1294 0,0987 0,0798 0, ,9970 0,9456 0,7667 0,5170 0,3844 0,3050 0,2526 0, ,9688 0,8232 0,5796 0,3516 0,1948 0,1345 0,1026 0,0830 0, ,9972 0,9474 0,7707 0,5212 0,3880 0,3080 0,2552 0, ,9728 0,8351 0,5939 0,3627 0,2017 0,1394 0,1065 0,0862 0, ,9974 0,9492 0,7747 0,5253 0,3915 0,3110 0,2577 0, ,9763 0,8461 0,6077 0,3737 0,2086 0,1444 0,1104 0,0893 0, ,9976 0,9510 0,7786 0,5294 0,3950 0,3140 0,2603 0, ,9794 0,8564 0,6211 0,3844 0,2154 0,1493 0,1142 0,0925 0, ,9978 0,9526 0,7824 0,5335 0,3985 0,3170 0,2629 0, ,9821 0,8660 0,6340 0,3950 0,2222 0,1542 0,1181 0,0956 0, ,9979 0,9542 0,7861 0,5375 0,4020 0,3199 0,2654 0, ,9844 0,8750 0,6464 0,4054 0,2289 0,1591 0,1219 0,0987 0, ,9980 0,9558 0,7898 0,5415 0,4054 0,3229 0,2680 0, ,9864 0,8834 0,6585 0,4156 0,2355 0,1639 0,1257 0,1019 0, ,9982 0,9573 0,7934 0,5455 0,4088 0,3258 0,2705 0, ,9882 0,8912 0,6701 0,4257 0,2421 0,1688 0,1294 0,1050 0, ,9983 0,9588 0,7969 0,5494 0,4122 0,3287 0,2730 0, ,9897 0,8985 0,6814 0,4355 0,2487 0,1735 0,1332 0,1081 0, ,9984 0,9602 0,8004 0,5533 0,4156 0,3316 0,2755 0, ,9910 0,9053 0,6922 0,4452 0,2552 0,1783 0,1370 0,1112 0, ,9985 0,9615 0,8039 0,5571 0,4190 0,3345 0,2780 0, ,9922 0,9116 0,7027 0,4547 0,2616 0,1830 0,1407 0,1142 0, ,9986 0,9628 0,8072 0,5609 0,4223 0,3374 0,2805 0, ,9932 0,9175 0,7128 0,4641 0,2680 0,1877 0,1444 0,1173 0, ,9987 0,9641 0,8105 0,5647 0,4257 0,3402 0,2830 0, ,9941 0,9231 0,7226 0,4733 0,2743 0,1924 0,1481 0,1204 0, ,9988 0,9653 0,8138 0,5685 0,4290 0,3431 0,2855 0, ,9948 0,9282 0,7321 0,4824 0,2805 0,1971 0,1518 0,1234 0, ,9989 0,9665 0,8170 0,5722 0,4322 0,3459 0,2880 0, ,9955 0,9330 0,7412 0,4913 0,2867 0,2017 0,1555 0,1264 0, ,9990 0,9676 0,8201 0,5759 0,4355 0,3488 0,2904 0, ,9961 0,9375 0,7500 0,5000 0,2929 0,2063 0,1591 0,1294 0, ,9990 0,9688 0,8232 0,5796 0,4388 0,3516 0,2929 0, ,9966 0,9417 0,7585 0,5086 0,2990 0,2109 0,1627 0,1325 0, ,9991 0,9698 0,8263 0,5832 0,4420 0,3544 0,2953 0, ,9970 0,9456 0,7667 0,5170 0,3050 0,2154 0,1664 0,1355 0, ,9991 0,9708 0,8292 0,5868 0,4452 0,3572 0,2978 0, ,9974 0,9492 0,7747 0,5253 0,3110 0,2199 0,1700 0,1385 0, ,9992 0,9718 0,8322 0,5903 0,4484 0,3600 0,3002 0, ,9978 0,9526 0,7824 0,5335 0,3170 0,2244 0,1735 0,1414 0, ,9993 0,9728 0,8351 0,5939 0,4516 0,3627 0,3026 0, ,9980 0,9558 0,7898 0,5415 0,3229 0,2289 0,1771 0,1444 0, ,9993 0,9737 0,8379 0,5974 0,4547 0,3655 0,3050 0, ,9983 0,9588 0,7969 0,5494 0,3287 0,2333 0,1807 0,1474 0, ,9994 0,9746 0,8407 0,6009 0,4579 0,3682 0,3074 0, ,9985 0,9615 0,8039 0,5571 0,3345 0,2378 0,1842 0,1503 0, ,9994 0,9755 0,8434 0,6043 0,4610 0,3709 0,3098 0, ,9987 0,9641 0,8105 0,5647 0,3402 0,2421 0,1877 0,1533 0, ,9994 0,9763 0,8461 0,6077 0,4641 0,3737 0,3122 0, ,9989 0,9665 0,8170 0,5722 0,3459 0,2465 0,1913 0,1562 0, ,9995 0,9771 0,8488 0,6111 0,4672 0,3764 0,3146 0, ,9990 0,9688 0,8232 0,5796 0,3516 0,2508 0,1948 0,1591 0, ,9995 0,9779 0,8513 0,6144 0,4703 0,3791 0,3170 0, ,9991 0,9708 0,8292 0,5868 0,3572 0,2552 0,1982 0,1620 0, ,9995 0,9787 0,8539 0,6178 0,4733 0,3818 0,3193 0, ,9993 0,9728 0,8351 0,5939 0,3627 0,2595 0,2017 0,1649 0, ,9996 0,9794 0,8564 0,6211 0,4764 0,3844 0,3217 0, ,9994 0,9746 0,8407 0,6009 0,3682 0,2637 0,2052 0,1678 0, ,9996 0,9801 0,8589 0,6243 0,4794 0,3871 0,3240 0, ,9994 0,9763 0,8461 0,6077 0,3737 0,2680 0,2086 0,1707 0, ,9996 0,9808 0,8613 0,6276 0,4824 0,3897 0,3264 0, ,9995 0,9779 0,8513 0,6144 0,3791 0,2722 0,2120 0,1735 0, ,9997 0,9814 0,8637 0,6308 0,4853 0,3924 0,3287 0, ,9996 0,9794 0,8564 0,6211 0,3844 0,2764 0,2154 0,1764 0, ,9997 0,9821 0,8660 0,6340 0,4883 0,3950 0,3310 0, ,9996 0,9808 0,8613 0,6276 0,3897 0,2805 0,2188 0,1793 0, ,9997 0,9827 0,8683 0,6371 0,4913 0,3976 0,3334 0, ,9997 0,9821 0,8660 0,6340 0,3950 0,2847 0,2222 0,1821 0, ,9997 0,9833 0,8706 0,6403 0,4942 0,4002 0,3357 0, ,9997 0,9833 0,8706 0,6403 0,4002 0,2888 0,2255 0,1849 0, ,9997 0,9838 0,8728 0,6434 0,4971 0,4028 0,3380 0, ,9998 0,9844 0,8750 0,6464 0,4054 0,2929 0,2289 0,1877 0, ,9998 0,9844 0,8750 0,6464 0,5000 0,4054 0,3402 0,2929

5 Tabel - U t (interval) T (periode) e decimaal ,0 0,0000 0,0069 0,0138 0,0206 0,0273 0,0341 0,0407 0,0474 0,0539 0,0605 0,1 0,0670 0,0734 0,0798 0,0862 0,0925 0,0987 0,1050 0,1112 0,1173 0,1234 0,2 0,1294 0,1355 0,1414 0,1474 0,1533 0,1591 0,1649 0,1707 0,1764 0,1821 0,3 0,1877 0,1934 0,1989 0,2045 0,2100 0,2154 0,2208 0,2262 0,2316 0,2369 0,4 0,2421 0,2474 0,2526 0,2577 0,2629 0,2680 0,2730 0,2780 0,2830 0,2880 0,5 0,2929 0,2978 0,3026 0,3074 0,3122 0,3170 0,3217 0,3264 0,3310 0,3357 0,6 0,3402 0,3448 0,3493 0,3538 0,3583 0,3627 0,3671 0,3715 0,3758 0,3801 0,7 0,3844 0,3887 0,3929 0,3971 0,4013 0,4054 0,4095 0,4136 0,4176 0,4217 0,8 0,4257 0,4296 0,4336 0,4375 0,4414 0,4452 0,4490 0,4529 0,4566 0,4604 0,9 0,4641 0,4678 0,4715 0,4751 0,4788 0,4824 0,4859 0,4895 0,4930 0,4965 1,0 0,5000 0,5035 0,5069 0,5103 0,5137 0,5170 0,5204 0,5237 0,5270 0,5302 1,1 0,5335 0,5367 0,5399 0,5431 0,5462 0,5494 0,5525 0,5556 0,5586 0,5617 1,2 0,5647 0,5677 0,5707 0,5737 0,5766 0,5796 0,5825 0,5853 0,5882 0,5910 1,3 0,5939 0,5967 0,5995 0,6022 0,6050 0,6077 0,6104 0,6131 0,6158 0,6184 1,4 0,6211 0,6237 0,6263 0,6289 0,6314 0,6340 0,6365 0,6390 0,6415 0,6440 1,5 0,6464 0,6489 0,6513 0,6537 0,6561 0,6585 0,6608 0,6632 0,6655 0,6678 1,6 0,6701 0,6724 0,6747 0,6769 0,6791 0,6814 0,6836 0,6857 0,6879 0,6901 1,7 0,6922 0,6943 0,6965 0,6985 0,7006 0,7027 0,7048 0,7068 0,7088 0,7108 1,8 0,7128 0,7148 0,7168 0,7187 0,7207 0,7226 0,7245 0,7264 0,7283 0,7302 1,9 0,7321 0,7339 0,7357 0,7376 0,7394 0,7412 0,7430 0,7447 0,7465 0,7483 2,0 0,7500 0,7517 0,7534 0,7551 0,7568 0,7585 0,7602 0,7618 0,7635 0,7651 2,1 0,7667 0,7684 0,7700 0,7715 0,7731 0,7747 0,7762 0,7778 0,7793 0,7808 2,2 0,7824 0,7839 0,7854 0,7868 0,7883 0,7898 0,7912 0,7927 0,7941 0,7955 2,3 0,7969 0,7983 0,7997 0,8011 0,8025 0,8039 0,8052 0,8066 0,8079 0,8092 2,4 0,8105 0,8118 0,8131 0,8144 0,8157 0,8170 0,8183 0,8195 0,8208 0,8220 2,5 0,8232 0,8244 0,8257 0,8269 0,8281 0,8292 0,8304 0,8316 0,8328 0,8339 2,6 0,8351 0,8362 0,8373 0,8385 0,8396 0,8407 0,8418 0,8429 0,8440 0,8450 2,7 0,8461 0,8472 0,8482 0,8493 0,8503 0,8513 0,8524 0,8534 0,8544 0,8554 2,8 0,8564 0,8574 0,8584 0,8594 0,8603 0,8613 0,8623 0,8632 0,8642 0,8651 2,9 0,8660 0,8670 0,8679 0,8688 0,8697 0,8706 0,8715 0,8724 0,8733 0,8741 3,0 0,8750 0,8759 0,8767 0,8776 0,8784 0,8793 0,8801 0,8809 0,8817 0,8826 3,1 0,8834 0,8842 0,8850 0,8858 0,8866 0,8873 0,8881 0,8889 0,8897 0,8904 3,2 0,8912 0,8919 0,8927 0,8934 0,8942 0,8949 0,8956 0,8963 0,8971 0,8978 3,3 0,8985 0,8992 0,8999 0,9006 0,9012 0,9019 0,9026 0,9033 0,9039 0,9046 3,4 0,9053 0,9059 0,9066 0,9072 0,9079 0,9085 0,9091 0,9098 0,9104 0,9110 3,5 0,9116 0,9122 0,9128 0,9134 0,9140 0,9146 0,9152 0,9158 0,9164 0,9170 3,6 0,9175 0,9181 0,9187 0,9192 0,9198 0,9203 0,9209 0,9214 0,9220 0,9225 3,7 0,9231 0,9236 0,9241 0,9246 0,9252 0,9257 0,9262 0,9267 0,9272 0,9277 3,8 0,9282 0,9287 0,9292 0,9297 0,9302 0,9307 0,9311 0,9316 0,9321 0,9325 3,9 0,9330 0,9335 0,9339 0,9344 0,9348 0,9353 0,9357 0,9362 0,9366 0,9371 4,0 0,9375 0,9379 0,9384 0,9388 0,9392 0,9396 0,9400 0,9405 0,9409 0,9413 4,1 0,9417 0,9421 0,9425 0,9429 0,9433 0,9437 0,9441 0,9444 0,9448 0,9452 4,2 0,9456 0,9460 0,9463 0,9467 0,9471 0,9474 0,9478 0,9482 0,9485 0,9489 4,3 0,9492 0,9496 0,9499 0,9503 0,9506 0,9510 0,9513 0,9516 0,9520 0,9523 4,4 0,9526 0,9530 0,9533 0,9536 0,9539 0,9542 0,9546 0,9549 0,9552 0,9555 4,5 0,9558 0,9561 0,9564 0,9567 0,9570 0,9573 0,9576 0,9579 0,9582 0,9585 4,6 0,9588 0,9591 0,9593 0,9596 0,9599 0,9602 0,9604 0,9607 0,9610 0,9613 4,7 0,9615 0,9618 0,9621 0,9623 0,9626 0,9628 0,9631 0,9633 0,9636 0,9639 4,8 0,9641 0,9644 0,9646 0,9648 0,9651 0,9653 0,9656 0,9658 0,9660 0,9663 4,9 0,9665 0,9667 0,9670 0,9672 0,9674 0,9676 0,9679 0,9681 0,9683 0,9685 5,0 0,9688 0,9690 0,9692 0,9694 0,9696 0,9698 0,9700 0,9702 0,9704 0,9706 5,1 0,9708 0,9710 0,9712 0,9714 0,9716 0,9718 0,9720 0,9722 0,9724 0,9726 5,2 0,9728 0,9730 0,9732 0,9734 0,9735 0,9737 0,9739 0,9741 0,9743 0,9744 5,3 0,9746 0,9748 0,9750 0,9751 0,9753 0,9755 0,9757 0,9758 0,9760 0,9762 5,4 0,9763 0,9765 0,9766 0,9768 0,9770 0,9771 0,9773 0,9774 0,9776 0,9777 5,5 0,9779 0,9781 0,9782 0,9784 0,9785 0,9787 0,9788 0,9789 0,9791 0,9792 5,6 0,9794 0,9795 0,9797 0,9798 0,9799 0,9801 0,9802 0,9804 0,9805 0,9806 5,7 0,9808 0,9809 0,9810 0,9812 0,9813 0,9814 0,9815 0,9817 0,9818 0,9819 5,8 0,9821 0,9822 0,9823 0,9824 0,9825 0,9827 0,9828 0,9829 0,9830 0,9831 5,9 0,9833 0,9834 0,9835 0,9836 0,9837 0,9838 0,9839 0,9840 0,9842 0,9843 6,0 0,9844 0,9845 0,9846 0,9847 0,9848 0,9849 0,9850 0,9851 0,9852 0,9853 6,1 0,9854 0,9855 0,9856 0,9857 0,9858 0,9859 0,9860 0,9861 0,9862 0,9863 6,2 0,9864 0,9865 0,9866 0,9867 0,9868 0,9869 0,9870 0,9870 0,9871 0,9872 6,3 0,9873 0,9874 0,9875 0,9876 0,9877 0,9877 0,9878 0,9879 0,9880 0,9881 6,4 0,9882 0,9882 0,9883 0,9884 0,9885 0,9886 0,9886 0,9887 0,9888 0,9889 6,5 0,9890 0,9890 0,9891 0,9892 0,9893 0,9893 0,9894 0,9895 0,9895 0,9896 6,6 0,9897 0,9898 0,9898 0,9899 0,9900 0,9900 0,9901 0,9902 0,9902 0,9903 6,7 0,9904 0,9904 0,9905 0,9906 0,9906 0,9907 0,9908 0,9908 0,9909 0,9910 6,8 0,9910 0,9911 0,9911 0,9912 0,9913 0,9913 0,9914 0,9915 0,9915 0,9916 6,9 0,9916 0,9917 0,9917 0,9918 0,9919 0,9919 0,9920 0,9920 0,9921 0,9921

6 Confédération Mondiale des Activités Subaquatiques World Underwater Federation DIVE COMPUTERS RECOMMENDATIONS C.M.A.S. Dive Computers Version 97/11 1

7 TABLE OF CONTENTS Preface Introduction Definitions - reminders Description and operating mode Instructions of utilisation a.- notice... 4 b.- planning mode Briefing... 4 a.- Compulsory material... 4 b.- Initialisation... 4 c.- Dive profiles... 4 d.- To respect the speed... 4 e.- Safety deco-stop... 4 f.- Strain... 4 g.- Cold Special proceedings:... 5 a.- Blow-up - Interruption of a deco-stop... 5 b.- Waves action... 5 c.- Break downs... 5 in single dives with a deco-stop... 5 in single dives without a deco-stop... 5 in succ.dives with a deco-stop... 5 in succ dives without a deco-stop... 5 d.- Flying after diving Limits of utilisation Careful / If I calculate them... I don t guarantee them The ideal instrument Synthesis Conclusions Consulted books... 7 C.M.A.S. Dive Computers Version 97/11 2

8 PREFACE Members from technical, scientific and medical commission co-operated to the writing of this document. We started with a document from the Belgian federation which has its own rules (law, insurance, US NAVY 1993 diving table, and so on...) That Belgian work was modified to be applied to CMAS. We thank all the people who collaborated to this work. Collaborators for : the technical committee Mr Jean RONDIA the scientific committee Dr Alain NORRO the medical commission Dr. Jean-Pierre MORTIER 1. INTRODUCTION As time goes on, computers have become a tool each time more performing and more available. CMAS have followed this evolution with the greatest care. With this in mind, it initiated its study and elaborated this syllabus concerted and conceived: By searching the application of long lasting and acceptable rules. By adopting a pragmatic and timeless aspect By making it assimilatory by the whole of the certified divers. By creating the bare bones of a Briefing type course, which favours the pedagogical aspect. 2. DEFINITION - REMINDERS: The use of a computer is allowed in pleasure dive only. Pleasure dive means any dive, whether single or successive, which do not include, test dive, exercise, training for/or taking exams to obtain any kind of brevet. If the computer will always suggest a solution to any given problem, one does not have to take for granted that the solution is applicable. The computer controls a limited number of parameters only. Further more, one has to underline that more recent will the model be, more performing will be the management of the decompression. The fact of utilising the computer does not grant dispensation from a thorough knowledge of the decompression tables. The computer will by all means, prove to be an excellent second to the confirmed diver. 3. DESCRIPTION AND FUNCTIONING MODE The initialisation is made by various methods: automatic, manual, shock, or by air pressure. The best known today remains the one by humid contact (automatic). The mathematical model, i.e. the Haldannien s type translated into a language that can be used by the computer, will integrate the time/depth information for each compartment and calculate at each instant, the theoretical nitrogen tension of each one of the model compartments. Comparing these tensions with the given values for the ascent criteria s will permit the calculation of the decompression. The Read Only Memory contains the programme with the characteristics of the utilised compartments, their periods, the characteristics, the ascent criterion which are associated to them, etc. etc. The Read Access Memory deals with the information in real time and works with the microprocessor. The microprocessor is the calculator allowing the exploitation of the information to reach the result: the decompression information on the display (screen). Numerous computers do not yet record infractions perpetrated in diving should the ascent speed or decompression proceedings not have been respected. Although a loud signal will be heard, no time nor proceedings change will be suggested. On the other hand, the ultimate generation of computers tends to register the infractions perpetrated as well as the relative formation of bubbles. Usually they will suggest procedures in order to remedy these situations. Obviously by not being in contact with the body tissues, the computer or the model mathematically included in its memory will not suggest any 100% reliable procedure of decompression as it remains based on mathematical results. Some new computers have air pressure and temperature sensors enabling to increase or fine tuning the decompression procedure in case of breathlessness or low temperature. They will also indicate solutions in case of blow-up or of interruptions of deco-stops. As a whole, these proceedings are just as acceptable as the diving table s procedures. ( UWATER AG, SWITZERLAND ) C.M.A.S. Dive Computers Version 97/11 3

9 4. ADVISE FOR UTILIZATION a.- NOTICE : Reading the instructions requires a thorough and definite understanding of the language. It is of paramount importance that these are read in a language mastered by the user. While in use, one will make sure to adhere strictly to the conditions preconised by the manufacturer. b.- PLANNING MODE: Single dives: enable the approximation of eventual deco stops before immersion (simulation) for a certain time and at a given depth. Successive dive: same + variation of the interval. The interesting point in this case lies on the successive made by divers who in the first dive would not have dived together. One can then determine a time as well as an accessible depth according to the parameters of the various computers, providing all of them are equipped with the planning function. In case of brake down, this mode may bring a solution ( see further) 5. BRIEFING a. COMPULSORY MATERIAL Watch : not all computers shows the hour ( departure ), in case of brake down, it may help you out of trouble. Tables : same + should one steps out of pleasure dive, one will have to refer to the decompression tables. Manometer : even if some computers give some simulated calculation of the consumption and of the availability of time according to the residual air quantity, we recommend however the utilisation of a classical manometer, to ease the various pressure controls and to avoid errors of interpretation or reading. b.- c.- d.- e.- f.- g.- INITIALISATION Check the starting process of the various models of the team. Even if most of them initialise automatically once in the water, it is advisable to initialise them manually to make sure on one hand, that they function properly, on the other for some models, to enable them to reach an accurate atmospheric pressure. DIVE PROFILE: Reminders of planning, stress the inverted profile s dangers once again. In as much as possible reach without delay the maximal depth decided during the briefing and then avoid to dive any deeper. Proscribe the borderline utilisation which consists in ascending a few meters as soon as the computer shows a time without a deco-stop near 0 (no dec. time). This tendency increases considerably the ADD risk. Should one of the members in the group not possess a computer, the most severe decompressure profile will be adopted, the one established before diving and/or at the start of the ascent. The group will remain together and everyone will step out of the water at the same time. Should members in the group possess different types of computers, here again the most severe protocol will be adopted, the group will remain together and everyone will step out of the water at the same time. TO RESPECT THE ASCENT SPEED Of the visual and/or by sound ascent decided during the briefing. SAFETY DECO-STOP Even if the computer does not show a deco-stop for the dive made, follow the rules pertaining to the federation s tables, but CMAS recommend a safety deco-stop of maximum 3' to 5' between 3mt and 6mt, should conditions be good. EFFORT In case of strain, break the dive immediately start an uninterrupted ascent at the prescribed speed (advertised), and effect the deco-stop eventually indicated and/or one safety deco-stop. COLD Even if some computers begin to integrate partially the factor temperature in their calculations, we recommend at this stage, in as much as possible with very low temperatures, to dive within the non decompression tables. C.M.A.S. Dive Computers Version 97/11 4

10 6. SPECIAL PROCEEDINGS a.- b.- c.- d.- BLOW-UP - INTERRUPTION OF DECO-STOPS Respect the indications and instructions supplied by the computer. If no indication (the manufacturer may not have kept these parameters in mind) apply your Federation s procedure for the decompression table s utilisation. WAVE ACTION Follow the computer indications as well but do never effect 3mt deco-stops below 6mt and follow the time given by the computer. COMPUTER BREAK DOWN Single dives without a deco-stop Go back to your Federation s decompression tables. The successive is authorised with this tables ( see decompression tables rules and methods). Single dives with deco-stops If deco-stops have not been started, refer above. If deco-stops have been started, bring the indicated decostops to an end. The successive is prohibited (24H) Successive dive without a deco-stop In case of failure, break the dive immediately, ascent at the recommended speed, do the safety deco-stop should conditions prevail. Successive dive with deco-stops If the computer is equipped with the planning mode, as soon as the failure appears break the dive immediately, ascent at the prescribed speed and effect the known deco-stops. If the computer should not be equipped with the planning mode, as soon as the failure appears, break the dive immediately, ascent at 6mt at the prescribed speed and effect a maximum of deco-stops at this depth (not at 3mt). N.B. : One shall note here again the advantage to have the planning mode. In the interval time, Prohibition to dive again within the next 24H as it is impossible to obtain parameters, allowing to calculate a successive. Flying after diving. Although the computer may say differently, always, await 24 hours prior to flying (DAN) NB : it is important to have read the notice carefully in order to know whether the computer has forecasted these instances. 7. UTILISATION LIMITS Refer to your federation s rules and to computer manual re : depth limits limits of authorised daily dives resting time (without a dive) after several days of successive dives factors favouring the ADD etc. One can go from the tables to the computer or vice versa. However this cannot be done as one may wish, one has to be desaturated to pass from the tables to the computer while inversely one has to wait for the total time of desaturation shown by the computer be null. 8. CAREFUL, IF I CALCULATE THEM...I DO NOT GUARANTEE THEM!!! Intensive dive Yo-yo dives (lift) Strain while diving Excessive depths dive Extreme conditions (cold) Non respect of deco-stops BLOW-UP To catch. an early flight C.M.A.S. Dive Computers Version 97/11 5

11 9. TODAY S IDEAL INSTRUMENT It should supply the followings: dive time maximal depth reached instantaneous depth detailed indications on deco-stops to be made: time and depth ascent speed with advertising either in % of a maximal speed, or in histogram intervals since out of the water to resolve the following problems: interruption of a deco-stop Blow-up planning mode low-battery indication alarm when no respect of the instrument utilisation rules (i.e. blow-up, etc. ) forecast altitude dives 10. SYNTHESES The 10 golden rules for diving with a computer : 1. Read and understand the instructions notice - read it again occasionally 2. Do not take everything for granted, respect strictly the manufacturer and your Federation s rules 3. Make sure of the good functioning of your instrument prior to putting it in the water 4. Remain as near as possible of the ideal profile and of the utiliation rules 5. Avoid the yo-yo dives, border line, hybrid 6. The computer is an individual and personal instrument 7. Do not use a computer saturated by someone else 8. Plan your dive and stick to your planning 9. Refer to the most severe decompression mode and remain grouped within the dive team 10. Remains a dive profile which offers a solution in case of break down In no case, these 10 rules prevent: 1. A thorough knowledge of the decompression tables 2. A diving experience 3. To limit the depth as per the rules of your federation 4. To respect a day of rest every 5 days in case of intensive diving 5. To effect the deepest depth first 6. Not to put oneself in a situation of exception 7. To avoid close successive dives. 11. CONCLUSIONS The diver s experience remains the first quality of a group leader and not the ownership of a computer, one can never trust blindly this instrument, it can be perfectible, your experience and your knowledge of the decompression tables could enable you to detect an eventual anomaly in its function. As a second in diving the computer is a definite plus. It is certainly not the panacea and does not prevent in any way the thorough learning of the tables. It is the perfect instrument for experienced divers. One does not give precision instruments to beginners. C.M.A.S. Dive Computers Version 97/11 6

12 12. CONSULTED BOOKS aladin pro aladin air X ( gestion d'air )+ fascicule "a new calculation model for the aladin air x diving computer" + fascicule "aladin air x personal decompression companion" suunto eon ( gestion d'air ) suunto alpha suunto solutions monitor 2 monitor 3 ( gestion d'air ) dc 11 dc 12 trak ( gestion d'air ) maestro pro ean ( gestion d'air ) bravo one scan 4 ( gestion d'air ) datamax sport datamax pro ( gestion d'air ) source dacor omni pro ( gestion d'air ) dive mate mares genius mares ( gestion d'air ) USNAVY DIVING MANUAL USNAVY DIVING TECHNICAL MANUAL 1983 DECOMPRESSION THEORY DIVE TABLES and Dive Computer J.E. LEWIS 1990 DIVE COMPUTER HISTORY,THEORY AND PERFORMANCE K.LOST 1991 PLONGER AUX MELANGES H.JUVENSPAN C.THOMAS 1992 L'ordinateur de plongée P. Bourdelet et A. Fuchs NEDU REPORTS 80 à 85 DECOMPRESSION AND COMPUTER ASSISTED DIVING Bob COLE INTERNET "Abyss advanced dive planning software " - "Aquanaut" - " IDCR-internet dive computer review" - "South africa charybdis" - " Nitrox //zeus.bris.ac.uk " DEEP DIVING bret Gilliam CMAS Conférence "Dive computers" Scientific Diving Supervisory Comittee : technical memorandum nr 2, March 92, published by NERC C.M.A.S. Dive Computers Version 97/11 7

13 Introduction to the Diving Safety Laboratory. Diving accidents are rare, fortunately, and are due to a variety of causes including those unrelated to diving such as heart attack or boat injuries. The fact that these accidents are rare does not mean that there is no need for active measures to reduce the number of accidents and improve safety. Diving techniques and diving safety can only be significantly improved by the active co-operation of the major organisations in diving, these are the diving industry, the diving medicine specialists and researchers and the divers themselves. This is what is happening here, DAN, the leading diver safety organisation and UWATEC, a leading dive computer and diving instruments manufacturer, have agreed to jointly set up a permanent research laboratory - the DAN - UWATEC Diving Safety Laboratory (DSL) - with the aim of examining all the relevant factors which may influence diver safety. This project will collect information on all forms of diving and diving accidents, with an emphasis on decompression illness, very much in a similar way to Project Safe Dive, but with the possibility of examining a number of situations where potential problems are believed to exist. In fact, this is a continuation of SAFE DIVE, which was initiated in 1993 following a proposal by Prof. Alessandro Marroni, President of DAN Europe. He believed that DAN Europe could organise a research project on the lines of the ongoing project on dive safety by DAN America but adapted to the European diving scene. Together with Dr Ramiro Cali-Corleo he developed the Safe Dive protocol and research kit. Now thanks to the generosity of UWATEC, who was also one of the original sponsors of Project Safe Dive, this has grown to a full dive laboratory. The success of this ambitious project depends on the participation of divers who are prepared to provide the DSL researchers with accurate information by correctly filling in the research questionnaires and by carrying with them, during their dives, the DSL 'Black Box' dive recorders. These divers will be under the discrete supervision of the DSL Bases and the Research Operators. The DSL Base is a diving school or store who is prepared to actively promote the DSL research program by prominently displaying the research posters and leaflets, encouraging divers to participate and acting as the location point for one or more DSL Research Kits. The DSL Bases will be identified by a special numbered wall plate. DSL Bases will automatically participate in the DAN - UWATEC Annual "DSL Base of the Year" Award. The Research Operator (RO for short) will be a specially trained diver (generally, but not exclusively, a dive instructor or dive-guide) who will assist the Research Divers (RD for short) in filling the research questionnaires and supervise the use of the DSL 'Black Box'. He will also work with the DSL Base in downloading the Black Boxes and uploading the data to the DAN Europe Research Division. The most active RO of the year will receive the DAN - UWATEC "Researcher of the Year" Award, which shall consist of one of UWATEC's latest dive computers and a commemorative wall plate. It is planned that the training of the ROs will be through a remote learning method, mainly using the Internet. This training method and the research forms are being developed with the assistance of Massimo Pieri and Piermario Maggiora, members of the DSL co-ordinating team. A sub-group of these divers will also be monitored for post dive bubble production through the use of specially developed recorders. The recordings will be carried out by a special group of divers (who are not only trained to be Research Operators but have also learned how to monitor a diver for post dive bubbles. These are the Research Technicians (these too will be generally, but not exclusively, dive instructors or dive-guides). These special ROs will be trained during seminars specially convened for that purpose. The monitoring for any post-dive gas bubbles is carried out using appropriate equipment, which was specifically chosen and modified for this task by Dr. Ramiro Cali-Corleo, with the assistance of Mr. Paolo Amico RAS (Italy). Some of the Research Technicians will also be taking part in special projects, where special groups of divers such as the diabetic or the handicapped diver will be monitored or where a particular diving technique or piece of equipment meriting study is being used. These are the Research Specialists. Research Technicians and Research Specialists are eligible for a separate "Annual DAN - UWATEC Research Award", which shall consist of one of UWATEC'S top line dive computers and a commemorative wall plate. The research team workers will be identified through the use of a special mask strap cover, which will carry the DSL logo and the researcher's status, that is, Research Operator, Research Technician, Research Specialist and Research Area Supervisor. DAN and UWATEC will be showing their appreciation to divers who participate through a number of rewards, which range from mask straps and T-shirts all the way to a full DAN Europe membership depending on the number of research dives the diver has participated in and logged in a special "Research Credit Record" card. Besides these rewards, the Research Diver who participates most every year will receive the "Research Diver of the Year" Award, which shall be one of UWATEC's latest dive computers. More details will be published in successive issues of Alert Diver. Look for the research page, which will also list the DSL bases. How does one participate? Simple, just send an to dsldcc@daneurope.org

14 THE USE OF A PROPORTIONAL M-VALUE REDUCTION CONCEPT (PMRC) CHANGING THE ASCENT PROFILE WITH THE INTRODUCTION OF EXTRA DEEP STOPS REDUCES THE PRODUCTION OF CIRCULATING VENOUS GAS EMBOLI AFTER COMPRESSED AIR DIVING. DSL SPECIAL PROJECT 01/2001 A. Marroni , R. Cali Corleo , C. Balestra , P. Longobardi 4-6, P. Germonpre E. Voellm 5-6, M. Pieri 1-6, R. Pepoli 6-7 1) DAN Europe Foundation, Research Division. 2) Division of Baromedicine, University of Malta Medical School. 3) Haute Ecole Paul Henry Spaak, Human Biology Dept. Bruxelles, Belgium. 4) Centro Iperbarico, Ravenna, Italy. 5) Dynatron AG and Uwatec AG, Swizterland. 6) DAN-UWATEC Diving Safety Laboratory. 7) Ravenna Sub, Ravenna, Italy. 8) Center for Hyperbaric Oxygen Therapy, Military Hospital Bruxelles. The DAN Europe SAFE DIVE project showed that post dive High Bubble Grades are directly related to Fast to Medium Half Time Tissues, Computed Nitrogen Venous Partial Pressure (PvenN 2 ) higher that 1100 mbar and Leading Tissue Nitrogen Partial Pressure (PltN 2 ) higher than 80% of the allowed M Value. A specific research project was started to identifying bubble-safe dive profiles based on the above findings. Three square dive profiles were selected: a single dive to 20 m for 60 min, a single dive to 40 m for 10 min, a series of three repetitive dives to 30 m for 16 min with 75 min Surface Interval. Table 1 General description of the four series of the five test dives Dive 1a 20 m 60 min Total Ascent Time Dive 2a 40 m 10 min Total Ascent Time 4 Dive 1b 20 m 60 min Total Ascent Time Dive 2b 40 m 10 min Total Ascent Time Dive 1c 20 m 60 min Total Ascent Time Dive 2c 40 m 10 min Total Ascent Time Dive 1d 20 m 60 min Total Ascent Time Dive 2d 40 m 10 min Total Ascent Time Dive 3.1a 30 m 16 min Dive 3.1b 30 m 16 min Dive 3.1c 30 m 16 min Dive 3.1d 30 m 16 min Total Ascent Time 3 25 SI 75 Total Ascent Time SI 75 Total Ascent SI 75 Time Total Ascent Time Dive 3.2a 30 m 16 min Dive 3.2b 30 m 16 min Dive 3.2c 30 m 16 min Dive 3.2d 30 m 16 min Total Ascent Time 6 25 SI 75 Total Ascent Time SI 75 Total Ascent Time SI 75 Total Ascent Time Dive 3.3a 30 m 16 min Dive 3.3b 30 m 16 min Dive 3.3c 30 m 16 min Dive 3.3d 30 m 16 min Total Ascent Time SI 75 Total Ascent Time SI 75 Total Ascent Time SI 75 Total Ascent Time Recording was performed every 15 minutes post dive. Grading was according to a variant of the Spencer method: Low Bubble Grade (L) occasional bubble detection; High Bubble Grade (H) frequent to continuous bubble detection. All dives were made according to the original ZH-L8 ADT model (Dive Series A) and repeated a first time with a new algorithm, modified in order to keep the PltN 2 within the above indicated limits (Dive Series B). 184 Recordings were made after 10 test chamber dives (90 man-dives) on 9 volunteers. 1

15 After Dive Series A, 5 of the 9 divers presented High Bubble Grades for extended time and 1 Diver suffered a mild episode of Skin Bend. Because of the limited sample, this figure was not considered as a DCS risk index higher than indicated by current epidemiological research, however we wanted to design dive profiles which could be safe even for high bubble risk divers. After Dive Series B only occasional Low Bubble Grades were registered. ( See previous reports from this group EUBS 2000 ) However the resulting ascent profiles were not considered diveable in the field, and a third profile (Dive Series C) was calculated, based on a different concept, introducing a gradual reduction of the Leading Tissue M- Value, inversely proportional to the Tissue HT (Proportional M-Value Reduction Concept PMRC). The fast to medium tissues M-Values were reduced by decreasing reduction factors, starting from a value of 0,3 for the faster tissue compartments, until the 80 minutes HT tissue, which was kept at the original M Value, according to the Buehlmann algorithm. The set of experimental dives was repeated with the same group of 9 volunteers, plus an additional 3 new divers, known as bubblers from previously monitored dives (Dive Series C). 96 Recordings were made during 5 test dives (60 man-dives) on 12 volunteers. After Dive Series C, 8 of the 12 Divers produced only occasional Low Bubble Grade signals, however the 20 meter dive produced constant LBG readings (and 1 HBG reading in one diver) in all the divers, over the entire 90 minutes post-dive monitoring period and this was considered as an index that the slow compartments M- Values were still too high. The PMR Concept was then applied to the 80 minutes HT tissues, reaching correction factor 1 for the 160 minutes HT. All the ascent profiles were re-calculated accordingly and were tested during a fourth series of chamber dives (Dive Series D) with 10 of the volunteers from the previous dives plus two female divers who had shown HBG readings during previous field exposures to normal dive profiles and had suffered multiple episodes of skin DCS. 108 Recordings were made during these last 5 test dives on 12 volunteers (60 man-dives). 6 of the 12 divers produced only minimal LBG readings, which were occasional in nature and did not show any clear pattern as to the post-dive time interval. Conclusions: the modification of the ZH-L8 ADT algorithm by the introduction of a Proportional M-Value Reduction Concept (PMRC) to the fast and medium-slow HT Tissue compartments, without altering the original speed of ascent to and between any planned stop and resulting in a modified ascent slope and in the introduction of extra deep stops during the ascent, eliminated the occurrence of significant post-dive detectable Venous Gas Emboli in a sample of 14 volunteers, during 20 dry test dives and 210 man-dives monitored with 388 Precordial Readings. The PMRC model has been entered into a new dive computer prototype which is currently being tested during multiple unrestricted recreational dives within the DAN UWATEC Diving Safety Laboratory program. 2

16 TABLES Table 2: Readings, Dive 1c: 20 meters / 60 min. Stops: 6 m / 6 min; 3 m / 20 min. RD Bubbler RS31 Medium +7 / / / L +58 / L +88 / L RS32 High +9 / / / H +59 / L +89 / L RS33 Medium +12 / / / L +61 / L +91 / L RS04 High +14 / L +27 / L +49 / L +62 / / 0 Table 3: Readings, Dive 1d. 20 m / 60 min. Stops 6 m / 10 min; 3 m / 23 min RD Bubbler RS31 Medium +2 / / / / L +71 / 0 RS32 High +4 / / / / / L RS33 Medium +6 / / / / L +75 / L RS04 High +8 / L +28 / / / / 0 Table 4: Readings, Dive 2c. 40 m, 10 min. Stops: 9m / 1min, 6 m / 3 min, 3 m / 6 min. RD Bubbler RS34 High +2 / L +19 / L +39 / L +54 / L +71 / L RS35 Low +4 / / / / / 0 RS36 Low +7 / / / / / 0 RS05 Low +10 / / / / / 0 Table 5: Readings, Dive 2d. 40 m / 10 min. Stops: 12m / 1 min; 9 m / 3 min; 6 m / 5 min; 3 m / 6 min. RD Bubbler RS34 High +5 / / L +33 / L +48 / L +63 / L +79 / 0 RS35 Low +7 / / / / / / 0 RS124 High +9 / / / / / / 0 RS125 High +11 / L +27 / / / / / 0 3

17 Table 6: Readings, Dive 3.1c. 30 m / 16 min. Stops: 6 m / 3 min, 3 m / 6 min. RD Bubbler RS37 Low +1 / / / / 0 RS38 Medium +4 / / / / 0 RS39 Medium +7 / / / / 0 RS20 Medium +9 / / / / 0 Table 7: Readings, Dive 3.2c. 30 m / 16 min. Stops: 6 m / 3 min, 3 m / 6 min. RD Bubbler RS37 Low +3 / / / / / L RS38 Medium +5 / / / L +53 / / 0 RS39 Medium +7 / / / / / 0 RS20 Medium +9 / / / L +57 / / 0 Table 8: Readings, Dive 3.3c. 30 m / 16 min. Stops: 6 m / 3 min, 3 m / 6 min. RD Bubbler RS37 Low +3 / / / / / 0 RS38 Medium +5 / / / / / 0 RS39 Medium +7 / / / / L +77 / 0 RS20 Medium +9 / / / / / 0 Table 9: Readings, Dive 3.1d. 30 m / 16 min. Stops: 9m / 2 min; 6 m / 5 min; 3 m / 7 min. RD Bubbler RS37 Low +1 / / / / / 0 RS38 Medium +3 / / / / / L RS39 Medium +5 / / / / / 0 RS20 Medium +7 / / / / / 0 4

18 Table 10: Readings, Dive 3.2d. 30 m / 16 min. Stops: 9m / 2 min; 6 m / 5 min; 3 m / 7 min. RD Bubbler RS37 Low +2 / / / / / 0 RS38 Medium +4 / / / / / 0 RS39 Medium +6 / / / / / 0 RS20 Medium +8 / / / / / 0 Table 11: Readings, Dive 3.3d. 30 m / 16 min. Stops: 9m / 2 min; 6 m / 5 min; 3 m / 7 min. RD Bubbler RS37 Low +1/ L +16 / / L +46 / / L +90 / 0 RS38 Medium +3 / / L +33 / L +48 / / L +92 / 0 RS39 Medium +5 / / / / L +79 / / 0 RS20 Medium +7 / L +22 / / / / / 0 5

19 References 1. Marroni A., Cali Corleo R. et Al. Project Safe Dive - a preliminary report. In: S.A. Sipinen, M. Leiniö (Eds), Proceedings of the XXI Annual Meeting of the EUBS; 1995: ISBN Marroni A, Cali-Corleo R, Denoble P. Understanding the safety of recreational diving. DAN Europe s Project SAFE DIVE Phase I: Fine tuning of the field research engine and methods Proceedings of the International Joint Meeting on Hyperbaric and Underwater Medicine, EUBS, ECHM, ICHM, DAN. Milano 4-8 September, 1996, p Marroni A, Cali Corleo R, Balestra C, Longobardi P, Voellm E, Pieri M, Pepoli R. Effects of the variation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. Paper Presented at the EUBS 2000 Annual Meeting, Malta September, Spencer MP, Johanson DC. Investigation of new principles for human decompression schedules using the ultrasonic blood bubble detector. Tech. Report to ONR on contract N C-0094, Institute for Environmental Medicine and Physiology, Seattle, Wash. USA Marroni A., Cali Corleo R., Balestra C., Voellm E, Pieri M. Incidence of Asymptomatic Circulating Venous Gas Emboli in unrestricted, uneventful Recreational Diving. DAN Europe s Project SAFE DIVE first results. EUBS 2000 Proceedings. Diving and Hyperbaric Medicine, Proceedings of the XXVI Annual Scientific Meeting of the European Underwater and Baromedical Society, R. Cali Corleo Ed. Malta September, 2000: Marroni A, Cali Corleo R, Balestra C., Longobardi P., Voellm E., Pieri, M., Pepoli R. Effects of the ariation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. EUBS 2000 Proceedings. Diving and Hyperbaric Medicine, Proceedings of the XXVI Annual Scientific Meeting of the European Underwater and Baromedical Society, R. Cali Corleo Ed. Malta September, 2000: 1-8 6

20 THE SPEED OF ASCENT DILEMMA: INSTANT SPEED OF ASCENT OR TIME TO SURFACE WHICH ONE REALLY MATTERS? INSTANT SPEED OF ASCENT VS. DELTA-P IN THE LEADING TISSUE AND POST-DIVE DOPPLER BUBBLE PRODUCTION. DSL SPECIAL PROJECT 02/2001 A. Marroni , R. Cali Corleo , C. Balestra , P. Longobardi 4-6, P. Germonpre E. Voellm 5-6, M. Pieri 1-6, R. Pepoli 6-7 1) DAN Europe Foundation, Research Division. 2) Division of Baromedicine, University of Malta Medical School. 3) Haute Ecole Paul Henry Spaak, Human Biology Dept. Bruxelles, Belgium. 4) Centro Iperbarico, Ravenna, Italy. 5) Dynatron AG and Uwatec AG, Swizterland. 6) DAN-UWATEC Diving Safety Laboratory. 7) Ravenna Sub, Ravenna, Italy. 8) Center for Hyperbaric Oxygen Therapy, Military Hospital Bruxelles. Fast ascent from any dive is universally considered as dangerous, even if anecdotal reports from the field offer contradictory interpretations. The DAN-UWATEC Diving Safety Laboratory findings indicated that the introduction of extra deep stops during the ascent, without changing the actual speed of ascent between the stops, resulted in the elimination of any significant post-dive precordial bubble detection. To better understand the role of the actual speed of ascent, which we defined as instant speed, we calculated this instant speed from the depth/time profile recorded with the DAN-UWATEC Diving Safety Laboratory Black Boxes (specially modified dive computers) every 20 seconds during the entire dive. A set of 20 experimental chamber dives was evaluated retrospectively, by comparing the instant speed of ascent of each single dive with the post-dive reading. The 20 dives were designed and calculated to test the modified decompression algorithm derived from the results of the DAN Diving Safety Laboratory Field Research Program, about which we reported at the EUBS 2000 Meeting and during this 2001 EUBS Annual Conference. Table 1 General description of the four series of the five test dives Dive 1a 20 msw 60 Total Ascent Time Dive 1b 20 msw 60 Total Ascent Time Dive 1c 20 msw 60 Total Ascent Time Dive 1d 20 msw 60 Total Ascent Time Dive 2a 40 msw 10 Total Ascent Time 4 Dive 3.1a 30 msw 16 Total Ascent Time 3 25 SI 75 Dive 2b 40 msw 10 Total Ascent Time Dive 3.1b 30 msw 16 Total Ascent Time SI 75 Dive 2c 40 msw 10 Total Ascent Time Dive 3.1c 30 msw 16 Total Ascent Time SI 75 Dive 2d 40 msw 10 Total Ascent Time Dive 3.1d 30 msw 16 Total Ascent Time Dive 3.2a 30 msw 16 Total Ascent Time 6 25 SI 75 Dive 3.2b 30 msw 16 Total Ascent Time SI 75 Dive 3.2c 30 msw 16 Total Ascent Time SI 75 Dive 3.2d 30 msw 16 Total Ascent Time Dive 3.3a 30 msw 16 Total Ascent Time SI 75 Dive 3.3b 30 msw 16 Total Ascent Time SI 75 Dive 3.3c 30 msw 16 Total Ascent Time SI 75 Dive 3.3d 30 msw 16 Total Ascent Time Recording was performed every 15 minutes post dive. Grading was according to a variant of the Spencer method: Zero: no bubbles detected. Low Bubble Grade (L) occasional bubble detection; High Bubble Grade (H) frequent to continuous bubble detection. Results Table 2 shows the observed grades after each experimental dive and the different values of peak instant speed of ascent and the average speed of ascent, not including the time spent at the prescribed decompression stops. 1

21 Table 2 Bubble grade, Peak and average Speed of ascent in meters / minute recorded during the 20 experimental dives ( Zero: no bubbles; LBG: Low Bubble Grades; HBG: High Bubble Grades) Dive 1a 20 msw 60 HBG Peak 9.41 Average 5.06 Dive 2a 40 msw 10 HBG+ (Skin Bend) Peak Average 7,96 Dive 3.1a 30 msw 16 HBG Peak Average 6.21 Dive 3.2a 30 msw 16 HBG Peak Average 6.36 Dive 3.3a 30 msw 16 HBG Peak 13,64 Average 7,94 Dive 1b 20 msw 60 Zero / LBG Peak 11,21 Average 3,22 Dive 2b 40 msw 10 Zero / LBG Peak Average 6.67 Dive 3.1b 30 msw 16 Zero / LBG Peak Average 5.14 Dive 3.2b 30 msw 16 Zero / LBG Peak Average 5.12 Dive 3.3b 30 msw 16 Zero / LBG Peak Average 4.62 Dive 1c 20 msw 60 LBG Peak Average 4.33 Dive 2c 40 msw 10 Zero / LBG Peak Average 7.56 Dive 3.1c 30 msw 16 Zero / LBG Peak 17,27 Average 6.02 Dive 3.2c 30 msw 16 Zero / LBG Peak Average 5.72 Dive 3.3c 30 msw 16 Zero / LBG Peak Average 6.31 Dive 1d 20 msw 60 Zero / LBG Peak Average 4.09 Dive 2d 40 msw 10 Zero / LBG Peak 10.3 Average 4.56 Dive 3.1d 30 msw 16 Zero / LBG Peak Average 5.45 Dive 3.2d 30 msw 16 Zero / LBG Peak Average 5.99 Dive 3.3d 30 msw 16 Zero / LBG Peak Average 4.9 Tables 3 and 4 show the actual readings for the two 40 meters dives which showed the most evidently discrepant difference in Peak Instant Speed of ascent Table 3: Readings, Dive 2a 40 meters 10 min. Ascent Time 4min. Peak instant speed 13,94 m/min, Average ascent speed 7.56 m/min RD Bubbler Time / Grade Time / Grade Time / Grade Time / Grade Time / Grade Time / Grade RS34 High +5 / L +18 / H +33 /H+L +48 / H+ +63 / H +79 / H RS35 Low +7 / / / L +50 / L +65 / L +81 / L Table 4: Readings, Dive 2c 40 meters 10 min. Ascent Time min. Peak instant speed m/min, Average ascent speed 7.96 m/min RD Bubbler Time / Grade Time / Grade Time / Grade Time / Grade Time / Grade Time / Grade RS34 High +5 / / L +33 / L +48 / L +63 / L +79 / 0 RS35 Low +7 / / / / / / 0 RS124 High +9 / / / / / / 0 RS125 High +11 / L +27 / / / / / 0 All the other dives showed similar patterns and the experimental dives, conducted with corrected algorithms and the introduction of reduced M Values and of extra deep stops, actually showed frequent laps of higher instant speed versus the normal dives conducted according to the original ZH-8 LDT algorithm. On the other hand, the average speed of ascent, not including the decompression stops, was not significantly different in any of the monitored dives. 2

22 40,00 37,00 37,00 35,00 33,00 30,00 29,10 24,70 23,30 20,00 20,30 17,30 13,00 10,00 8,40 6,30 4,10-0,46 1,90 0,00 0,00 0, ,24-5,88-6,06-6,18-5,59-6,67-9,09-8,82-6,67-10,00-11,82-12,94-13,03-13,94-20,00 Table 5. Dive to 40 meters 1. Average speed of ascent 7.96 m/min. Peak speed 12,94 m/min 50,00 40,00 39,50 39,50 36,90 36,90 30,00 28,60 24,80 20,00 16,70 11,30 10,00 9,70 7,80 7,80 6,60 4,50 4,50 0,00 2,20 2,20 0,00 0,00 0,00 0,00-0,16-1,12-1,90-0,70 0,00-0,23-4,85-3,53-2,73-6,67 0, ,00-11,52-15,88-20,00-24,41-24,55-30,00 Table 6. Dive to 40 meters 2. Average speed of ascent 7.56 m /min Peak speed m/min 3,60 3

23 Tables 5 and 6 show the charts of the two 40 meter dives with the actual figures of the variations of the speed of ascent during all the decompression phase, clearly showing the peaks of the instant speed and its variations in time. 35,00 10,00 30,00 28,30 8,60 8,00 25,00 20,00 26,10 25,20 24,20 22,80 22,80 22,00 20,60 18,80 17,20 6,00 4,00 7,00 5,30 4,10 15,00 15,50 10,00 13,40 12,50 11,10 9,40 2,00 5,00 0,00 0,00 0, ,00-1,19-3,33-2,65-1,52 0, ,09-1, ,73-5,00-4,24-4,24-5,29-4,85-5,15-6,18-5,00-2,00-4,00-2,42-4,85-5,00-3,64-1,76-10,00-6,00 Table 7 Peak and average ascent speed on a 30 meter open water dive followed by neurological DCI The two charts shown in tabe 7 above refer to an open water dive to 30 meter. Bottom time 21 minutes, followed by an apparently regular ascent, a 2 minute safety stop at 4 meters followed by immediate ascent to the surface. The ZH8-LDT algorithms signaled M Values of the fast and medium compartments reaching 100%. The diver reported neurosensory symptoms of DCI about 30 minutes after the dive and was successfully treated. Peak instant speed of ascent was never faster than 5 meter /minute, with an average ascent speed ( not including the decompression stops) of 2.9 m/min. We could observe three other similar decompression injuries occurring after real dives monitored within the DAN Europe Diving Safety Laboratory and in all these cases we could not observe any evident correlation with fast instant ascent speeds, but only with the computed M Values in the leading tissues, according to the ZH8-LDT algorithm. Conclusions We could not observe any direct correlation between instant speed and post-dive bubble detection during our 20 experimental dives and from the recorded dive profiles of four decompression injuries monitored within the DAN Europe Diving Safety Laboratory. Contradictory results were actually observed during several test chamber dives. During the experimental chamber dives, computed according to the new Proportional M-Value Reduction Concept and introducing extra deep stops during the decompression phase and with instant speeds of up to 24,55 meters per minute we had no bubble signal detection; on the contrary, we observed high bubble grade signals after the control dives, made according to the standard ZH-L8 ADT algorithm, with instant speeds of ascent never faster than 13 meters per minute. These preliminary observations seem to indicate that the Delta-P imposed on the leading tissue, irrespective of the instant speed of ascent, is the only critical factor for precordially detectable bubble production in this series of experimental dives, and, possibly, for the development of DCI in real dives. This may imply certain revisions on currently accepted recreational diving practices, with regard to the optimal ascent modality and is consistent with our previously reported observations about the positive effect of modifying the ascent profile by the introduction of extra deep stops. Further analysis on real unrestricted recreational dives is planned within the DAN-UWATEC Diving Safety Laboratory program. 4

24 References 1. Marroni A., Cali Corleo R. et Al. Project Safe Dive - a preliminary report. In: S.A. Sipinen, M. Leiniö (Eds), Proceedings of the XXI Annual Meeting of the EUBS; 1995: ISBN Marroni A, Cali-Corleo R, Denoble P. Understanding the safety of recreational diving. DAN Europe s Project SAFE DIVE Phase I: Fine tuning of the field research engine and methods Proceedings of the International Joint Meeting on Hyperbaric and Underwater Medicine, EUBS, ECHM, ICHM, DAN. Milano 4-8 September, 1996, p Marroni A, Cali Corleo R, Balestra C, Longobardi P, Voellm E, Pieri M, Pepoli R. Effects of the variation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. Paper Presented at the EUBS 2000 Annual Meeting, Malta September, Spencer MP, Johanson DC. Investigation of new principles for human decompression schedules using the ultrasonic blood bubble detector. Tech. Report to ONR on contract N C-0094, Institute for Environmental Medicine and Physiology, Seattle, Wash. USA Marroni A., Cali Corleo R., Balestra C., Voellm E, Pieri M. Incidence of Asymptomatic Circulating Venous Gas Emboli in unrestricted, uneventful Recreational Diving. DAN Europe s Project SAFE DIVE first results. EUBS 2000 Proceedings. Diving and Hyperbaric Medicine, Proceedings of the XXVI Annual Scientific Meeting of the European Underwater and Baromedical Society, R. Cali Corleo Ed. Malta September, 2000: Marroni A, Cali Corleo R, Balestra C., Longobardi P., Voellm E., Pieri, M., Pepoli R. Effects of the ariation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. EUBS 2000 Proceedings. Diving and Hyperbaric Medicine, Proceedings of the XXVI Annual Scientific Meeting of the European Underwater and Baromedical Society, R. Cali Corleo Ed. Malta September, 2000: 1-8 5

25 INCIDENCE OF ASYMPTOMATIC CIRCULATING VENOUS GAS EMBOLI IN UNRESTRICTED, UNEVENTFUL RECREATIONAL DIVING. SKIN COOLING APPEARS TO BE RELATED TO POST-DIVE DOPPLER DETECTABLE BUBBLE PRODUCTION. AN UNEXPECTED FINDING. DSL SPECIAL PROJECT A. Marroni , R. Cali Corleo , C. Balestra , P. Longobardi 4-6, P. Germonpre 1-2-8,, E. Voellm 5-6, M. Pieri 1-6, R. Pepoli 6-7 1) DAN Europe Foundation, Research Division. 2) Division of Baromedicine, University of Malta Medical School. 3) Haute Ecole Paul Henry Spaak, Human Biology Dept. Bruxelles, Belgium. 4) Centro Iperbarico, Ravenna, Italy. 5) Dynatron AG and Uwatec AG, Swizterland. 6) DAN-UWATEC Diving Safety Laboratory. 7) Ravenna Sub, Ravenna, Italy. 8) Center for Hyperbaric Oxygen Therapy, Military Hospital Bruxelles. Between 1995 and 1999, DAN Europe collected 2105 fully monitored unrestricted recreational dives, during 75 Research Trips organized by 106 Research Field Operators and involving 575 volunteer Research Divers. All the dives were monitored at fixed intervals post-dive. The distribution by depth of the monitored dives showed that the relative majority (33,15%) of the dives were made in the 20 to 30 meters depth range. The Overall depth range varied from 5 to 65 meters. Table 1. Distribution by depth of the 1418 monitored dives Depth >50 Percent 4,65 23,42 33,15 23,97 12,97 1,84 monitored bubbles were detected in 37 % of all the monitored dives. 25% of the dives produced Low Bubble Grade recordings only, while 12% produced High Bubble Grades. Repetitive dives showed a reversed incidence of post dive VGE, as only 15% of the repetitive dives were bubble-free, LBG were detected in 18% of the repetitive dives and HBG were recorded in 67% of the repetitive dives. Table 2. Incidence of Bubble Signals after all the dives and after the repetitive dives separately. DBG Zero LBG HBG All Dives 63% 25% 12% Rep Dives 15% 18% 67% A further analysis of the dives showed an unexpected finding, when considering the estimated skin cooling, calculated by the dive profile recorder as a function of time and water temperature. HBG doppler signals appeared to be related to estimated skin cooling, with higher signal for skin temperatures of 26,5-27 C and low or absent signals for skin temperatures of 29 C. Table 3 Estimated skin temperatures versus post dive Precordial Bubble Detection after unrestricted recreational dives monitored during DAN Europe Project Safe Dive. Skin Temp C 29, , , , ,5 25 Ze ro LB G HB G HB G+ Although these data refer to estimated and not measured skin cooling, they suggest a more important than previously considered role of the skin in the production and release of post-dive circulating venous gas emboli and a concomitant role of temperature and heat-loss. 1

26 It is hypothesized that diving in relatively cold water produces progressive skin cooling and vasoconstriction that may, by the end of the dive and during the post-dive period, produce a temporary trapping of excess inert gas in the skin compartment, producing significant local supersaturation and gas phase formation during the ascent and the immediate post-dive period. The subsequent post-dive skin re-warming, with removal of the vasoconstriction, may produce a significant release of venous bubbles and showers of bubbles invading the pulmonary circulation. This reminds the frequently reported anecdotal post-dive hot shower effect. The role of these variables, as well as the effects of various exposure suits and thermal balance control systems will be investigated during experimental as well as unrestricted field dives, including Monitoring and real continuous skin and body temperature monitoring, within the DAN UWATEC Diving Safety Laboratory program. References 1. Marroni A., Cali Corleo R. et Al. Project Safe Dive - a preliminary report. In: S.A. Sipinen, M. Leiniö (Eds), Proceedings of the XXI Annual Meeting of the EUBS; 1995: ISBN Marroni A, Cali-Corleo R, Denoble P. Understanding the safety of recreational diving. DAN Europe s Project SAFE DIVE Phase I: Fine tuning of the field research engine and methods Proceedings of the International Joint Meeting on Hyperbaric and Underwater Medicine, EUBS, ECHM, ICHM, DAN. Milano 4-8 September, 1996, p Marroni A, Cali Corleo R, Balestra C, Longobardi P, Voellm E, Pieri M, Pepoli R. Effects of the variation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. Paper Presented at the EUBS 2000 Annual Meeting, Malta September, Spencer MP, Johanson DC. Investigation of new principles for human decompression schedules using the ultrasonic blood bubble detector. Tech. Report to ONR on contract N C-0094, Institute for Environmental Medicine and Physiology, Seattle, Wash. USA Marroni A., Cali Corleo R., Balestra C., Voellm E, Pieri M. Incidence of Asymptomatic Circulating Venous Gas Emboli in unrestricted, uneventful Recreational Diving. DAN Europe s Project SAFE DIVE first results. EUBS 2000 Proceedings. Diving and Hyperbaric Medicine, Proceedings of the XXVI Annual Scientific Meeting of the European Underwater and Baromedical Society, R. Cali Corleo Ed. Malta September, 2000: Marroni A, Cali Corleo R, Balestra C., Longobardi P., Voellm E., Pieri, M., Pepoli R. Effects of the ariation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. EUBS 2000 Proceedings. Diving and Hyperbaric Medicine, Proceedings of the XXVI Annual Scientific Meeting of the European Underwater and Baromedical Society, R. Cali Corleo Ed. Malta September, 2000: 1-8 2

27 Effects of the variation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000 A. Marroni , R. Cali Corleo , C. Balestra , P. Longobardi 4-6, E. Voellm 5-6, M. Pieri 1-6, R. Pepoli 6-7 1) DAN Europe Foundation, Research Division. 2) Division of Baromedicine, University of Malta Medical School. 3) Haute Ecole Paul Henry Spaak, Human Biology Dept. Bruxelles, Belgium. 4) Centro Iperbarico, Ravenna, Italy. 5) Uwatec AG, Hallwill, Swizterland. 6) DAN - UWATEC Diving Safety Laboratory. 7) Ravenna Sub, Ravenna, Italy Introduction The first results of the DAN Europe SAFE DIVE project, obtained from 1418 recreational dives fully monitored according to the original DAN Europe SAFE Dive Protocol ( 1, 2, 3) showed that post dive High Bubble Grades (HBG), as detected with a Ultrasound Bubble Detector ( DAN Europe Design, 1,2), graded according to the Spencer Method (4), modified by DAN Europe for this particular field use (3), and correlated to the electronically downloaded dive profiles, are directly related to: 1) Fast to Medium Half Time Tissues according to the UWATEC ZH-L8 ADT model 2) Computed Nitrogen Venous Partial Pressure (PvenN 2 ) higher that 1100 mbar 3) Computed Leading Tissue Nitrogen Partial Pressure (PltN 2 ) higher than 80% of the allowed M Value for that tissue. 4) Total Decompression Debit expressed as computed residual No-D time or computed Time to Reach Surface. 5) Absolute Depth of the Dive 6) Repetitive Dives 7) The fact that no evident correlation could be found between HBG and the fractional speed of ascent at any given time of the ascent. Materials and Methods DAN Europe and UWATEC, within the common research project known under the name of DAN- UWATEC Diving Safety Laboratory, started a specific research protocol (DSL Special Project 01/2000), aimed at identifying bubble-safer dive profiles and based on the findings of DAN Europe Project SAFE DIVE. Three relatively common square dive profiles were selected: a single dive to 20 meters for 60 minutes bottom time ( including 1 40 descent ) a single dive to 40 meters for 10 minutes bottom time ( including 3 01 descent ) a series of three repetitive dives to 30 meters for 16 minutes bottom time ( including 2 40 descent) with 75 Surface Interval between them. The dives were made according to the original ZH-L8 ADT model an repeated one week after with the same group of divers and a modified algorhythm.

28 The new model was designed without changing the original fractional speed of ascent and was aimed at keeping the PvenN 2 below 1100 mbar and the PltN 2 below 80% of the allowed M Value. The five dives 2 single, 3 repetitive were made by 3 groups of 3 volunteer divers of the Dive Club Ravenna Sub, who had been informed about the scopes and the modality of the test and knew that they would have dived according to standard tables on their first dive series and on experimental tables on the second dive series. All the divers signed and informed consent form, as requested by the Clinical Hyperbaric Facility and the DAN Europe Research Division. The two series of dives were performed on two consecutive Saturdays, to allow for complete desaturation of the divers between the dives, and all the divers accepted not to dive on their own in the interval. The dives were performed in the Multiplace Hyperbaric Chambers of the Centro Iperbarico di Ravenna, Italy. Three couples of Black Boxes modified UWATEC computers as described in our previous work (1,2) - were kept in the chamber during each of the five different dives, and the same couples were used the following Saturday for the second dive series, assuring that the same computers were used for the same dive series. To assure that the Black Boxes worked properly, they were immersed in water all the time during the chamber dives. Of the 9 volunteer divers, 3 one for each dive series - were known Bubblers form previous SAFE DIVE Research Trips organized by the Dive Club Ravenna Sub. Recording were performed by a member of the Research Team, every 15 minutes after the dives, up to 75 or 90 minutes, and evaluated subsequently in undisturbed laboratory conditions. We graded the Bubble Signals according to the Spencer Scale (4) and also according to a Bubble Grading System that we designed, as a variant of the Spencer method, as follows: LBG Low Bubble Grade: occasional bubble signals, Bubble Grades (DBG) lower than 2 in the Spencer Scale HBG High Bubble Grade: Frequent to continuous bubble signals, DBG higher than 2 in the Spencer scale. Occasional very high DBG were rated HBG+ grading, when bubble signals reached grade 4 in the Spencer scale. Results Dive series 1 20 meters 60 minutes. Both dives clinically uneventful Dive 1a Depth Total Ascent Time Dive 1b Depth Tot. Asc. Time

29 Readings Dive series 1 Dive 1a 20 meters 60 minutes total ascent time 17,30 minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes 90 minutes RS31 Medium RS32 High RS33 Medium Dive 1b 20 meters 60 minutes total ascent time 31,25 minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes RS31 Medium RS32 High 0 0, RS33 Medium minutes Grades Dive 1 Graph 1. Bubble Grades after the 20 meter dive series for standard (upper curve) and modified profiles (lower curve). Grade Dive 1a / RS31 Dive 1a / RS33 Dive 1a / RS32 Dive 1b / RS31 Dive 1b / RS33 Dive 1b / RS32 Avg. 1a Avg. 1b Polynomisch (Avg. 1a) Polynomisch (Avg. 1b) Time [min] Dive Series 2 40 meters 10 minutes. Dive 2a produced Skin DCI in diver RS34 Dive 2a Depth Total ascent Time Dive 2b Depth Tot Asc Time

30 readings Dive Series 2 Dive 2a 40 meters 10 minutes total ascent time 4 minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes 90 minutes RS34 High RS35 Low RS36 Low Dive 2b 40 meters 10 minutes total ascent time minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes RS34 High RS35 Low RS36 Low minutes Grades Dive 2 Skin Bend Dive 2a / RS35 Dive 2a / RS36 Graph 2. Bubble Grades after the 40 meter dive series for standard (upper curve) and modified profiles (lower curve). Grade Dive 2a / RS34 Dive 2b / RS35 Dive 2b / RS36 Dive 2b / RS34 Avg. 2a Polynomisch (Dive 2b / RS35) Polynomisch (Dive 2b / RS36) Polynomisch (Dive 2b / RS34) Polynomisch (Avg. 2a) Time [min] Dive Series 3 30 meters 16 minutes. Three repetitive dives with 75 minutes surface interval. All Dives clinically uneventful. Dive Series 3a 3.1a Depth Total ascent Time a Depth Tot asc Time a Depth Tot asc Time

31 Dive Series 3b 3.1b Depth Tot asc Time b 75 minutes surface interval Depth Tot asc Time b 75 minutes surface interval Depth Tot asc Time Readings. Dive Series 3 First Dive Dive 3.1a 30 meters 16 minutes total ascent time 3.25 minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes 90 minutes RS37 Low RS38 High RS39 Medium Dive 3.1b 30 meters 16 minutes total ascent time minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes RS37 Low RS38 High RS39 Medium minutes First Repetitive Dive Dive 3.2a 30 meters 16 minutes total ascent time 6.25 minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes 90 minutes RS37 Low RS38 High RS39 Medium Dive 3.1b 30 meters 16 minutes total ascent time minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes RS37 Low RS38 High RS39 Medium minutes

32 Second Repetitive Dive Dive 3.3a 30 meters 16 minutes total ascent time minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes 90 minutes RS37 Low RS38 High RS39 Medium Dive 3.3b 30 meters 16 minutes total ascent time minutes Research Diver Bubbler 15 minutes 30 minutes 45 minutes 60 minutes 75 minutes RS37 Low RS38 High RS39 Medium minutes 4 3,5 Grades Dive 3.1 Graph 3.1. Bubble Grades after the first dive of the repetitive dive series for standard (upper curve) and modified profiles (lower curve). 3 2,5 2 1,5 1 Dive 3.1a / RS37 Dive 3.1a / RS38 Dive 3.1a / RS39 Dive 3.1b / RS37 Dive 3.1b / RS38 Dive 3.1b / RS39 Avg. 3.1a Avg. 3.1b Poli. (Avg. 3.1a) Poli. (Avg. 3.1b) 0, Time [min] 4 3,5 Grades Dive 3.2 Graph 3.2. Bubble Grades after the second dive of the repetitive dive series for standard (upper curve) and modified profiles (lower curve). 3 2,5 2 1,5 1 Dive 3.2a / RS37 Dive 3.2a / RS38 Dive 3.2a / RS39 Dive 3.2b / RS37 Dive 3.2b / RS38 Dive 3.2b / RS39 Avg. 3.2a Avg. 3.2b Poli. (Avg. 3.2a) Poli. (Avg. 3.2b) 0,5 ssssssss Time [min]

33 - 4 3,5 Grades Dive 3.3 Graph 3.3. Bubble Grades after the third dive of the repetitive dive series for standard (upper curve) and modified profiles (lower curve). 3 2,5 2 1,5 1 Dive 3.3a / RS37 Dive 3.3a / RS38 Dive 3.3a / RS39 Dive 3.3b / RS37 Dive 3.3b / RS38 Dive 3.3b / RS39 Avg. 3.3a Avg. 3.3b Poli. (Avg. 3.3a) Poli. (Avg. 3.3b) 0, Time [min] General Results During the series of 10 test dives ( 5 with a regular profile and 5 with the experimental profile), 184 Recordings were made on the 9 volunteer Divers. After Dive Series A - Regular Profile - 5 of the 9 Divers presented High Bubble Grades for extended time and 1 Diver suffered a mild episode of Skin Bend, which was promptly and successfully treated. After the Dive Series B - Experimental Profile - we could only monitor occasional Low Bubble Grades and all the dives were uneventful. Dives A produced 6,3% DBG Zero, 58,2% LBG, 25,3% HBG and 10,2% HBG+. On the contrary Dives B produced 60,8% DBG Zero, 39,2% LBG and no incidence of HBG (See Table below). Table I. Bubble Grades after Regular (A) and Experimental (B) Dive Profiles DBG Zero LBG HBG HBG+ DIVES A 6.3% 58.2% 25.3% 10.2% DIVES B 60.8% 39.2% Conclusions The introduction of extra deep stops in the ascent profile from compressed air dives, without changing the fractional speed of ascent at any time, and keeping the computer-estimated PvenN 2 and PltN 2 levels within 1100 mbars and 80% of the allowed M Value, respectively, as suggested by the first results of DAN Europe Project SAFE DIVE, greatly reduced detected Bubble production in a sample of volunteer divers exposed to regular and experimental dive profiles and being their own control during the two consecutive chamber dive series. Re-calculating the deep phases of decompression, through an alteration of the overall ascent slope, aimed at reducing the Pressure Differential imposed on the Fast to Medium Half Time Tissue Compartments ( minutes according to the UWATEC ZH-L8 ADT Model) and to keep PvenN 2

34 and PltN 2 within the above indicated limits, may be effective in preventing gas nucleation during decompression from compressed air dives. References 1. Marroni A., Cali Corleo R. et Al. Project Safe Dive - a preliminary report. In: S.A. Sipinen, M. Leiniö (Eds), Proceedings of the XXI Annual Meeting of the EUBS; 1995: ISBN Marroni A, Cali-Corleo R, Denoble P. Understanding the safety of recreational diving. DAN Europe s Project SAFE DIVE Phase I: Fine tuning of the field research engine and methods Proceedings of the International Joint Meeting on Hyperbaric and Underwater Medicine, EUBS, ECHM, ICHM, DAN. Milano 4-8 September, 1996, p Marroni A, Cali Corleo R, Balestra C, Longobardi P, Voellm E, Pieri M, Pepoli R. Effects of the variation of Ascent Speed and Profile on the production of Circulating Venous Gas Emboli and the Incidence of DCI in Compressed Air Diving. Phase 1. Introduction of extra deep stops in the ascent profile without changing the original ascent rates. DSL Special Project 01/2000. Paper Presented at the EUBS 2000 Annual Meeting, Malta September, Spencer MP, Johanson DC. Investigation of new principles for human decompression schedules using the ultrasonic blood bubble detector. Tech. Report to ONR on contract N C-0094, Institute for Environmental Medicine and Physiology, Seattle, Wash. USA. 1974

35 Smart MICROBUBBLE MANAGEMENT

36 S M A R T M I C R O B U B B L E M A N A G E M E N T 2 The Smart COM displays the cylinder pressure, calculates and displays the Remaining Bottom Time (RBT), and warns when RBT is less than 3 minutes. Displays tank pressure - psi (bar) Remaining dive time at current depth (RBT) User adjustable tank reserve warning Low air warning Quantity of air used RBT is less than 3 alarm RBT less than 0 alarm ADAPTIVE COMPUTERS Smart PRO Wrist GAS CONSUMPTION UWATEC dive computers have long included the Bühlmann ZH-L8 ADT mathematical model that allows the computer to adapt to actual diver behaviors and environmental conditions. The name of the model was derived from ZH - Zurich where the model was developed, L8 refers to the number of body tissue groups that the model considers and ADT is short for adaptive. With an adaptive model, if a diver exceeds the prescribed ascent rate, works too hard, or is exposed to really cold water, the dive computer may ask the diver to complete a compensation decompression stop. Another advantage of the adaptive model is that it allows UWATEC dive computers to more accurately predict the remaining gas requirements on deep dives and it provides more accurate monitoring of the CNS loading for Nitrox divers. UWATEC has now proven that divers who conduct repetitive dives even within the standard no decompression limits produce microbubbles. Microbubbles may be a precondition for the formation of larger bubbles that can lead to decompression illness. Microbubbles usually present no visible symptoms to the diver, but may cause permanent damage. Divers with a PFO (Patent Foramen Ovale - a hole between the two chambers of the heart) are particularly susceptible. With two additional letters, the Bühlmann adaptive model has been expanded to be called the ZH-L8 ADT MB. This stands for microbubble, because the UWATEC Smart can be programmed for microbubble suppression. Smart PRO Console Smart COM On deeper dives, divers need to carry sufficient gas reserves to ascend and complete any necessary decompression stops. The Smart COM displays a Remaining Bottom Time field, which is an estimate of the time remaining at the current depth until an ascent must be commenced. Once the ascent commences, the Smart COM has already included a prediction of the gas reserves necessary to ascend at the prescribed ascent rate and complete the necessary decompression stops. The baseline for the RBT is the tank reserve value which can be set via Smart TRAK in 5 bar increments between 20 and 120 bar. An RBT of 0 means that if an ascent is commenced at that time and carried out at the correct ascent rate, respecting all decompression stops, the diver will be on the surface with approximately the tank reserve left in the tank. The calculation is based on the diver s current rate of gas consumption, temperature and the current tank pressure and starts 1.5 minutes after the start of a dive. It is updated every 4 seconds. The computer accurately modifies the Remaining Bottom Time according to variations in the diver s rate of breathing. If the diver is experiencing heavy exertion, then the RBT is reduced. If the diver is relaxed, then the RBT is extended. The accuracy of this calculation is due to the pressure sensor s ability to accurately measure a single breath of air. The accuracy is further enhanced because it considers the ambient temperature and air pressure is affected by ambient temperature variations. This is particularly useful for a diver who is diving through thermoclines. At the conclusion of a dive the Smart COM displays the differential pressure. This value represents the gas that is consumed during the dive. Also displayed are any warnings that may have occurred throughout the dive, in this example both RBT and Workload warnings are displayed. After a dive, the data from the Smart COM can be downloaded to Personal Computer with the Smart TRAK software that is included with the Smart COM. The actual rate of breathing is displayed in l/min, as is the workload level. Also displayed is microbubble buildup and temperature.

37 S M A R T M I C R O B U B B L E M A N A G E M E N T 4 The Smart COM considers the effect that exertion has on the decompression schedule. When the lung symbol appears the diver should relax the breathing rate. The Smart PRO and Smart COM include the effect of temperature on the decompression schedule and display both the ambient and water temperature. High breathing rate alarm (High Air Consumption) Adaptive decompression model Bühlmann ZH-L8 ADT MB CNS clock is adjusted by O 2 uptake according to workload User adjustable air workload warning Workload is displayed in Smart TRAK Displays ambient temperature, on the surface Measures and displays water temperature Includes temperature in decompression model Logs temperature (dive computer) Logs temperature (Smart TRAK) W ORKLOAD TEMPERATURE Some dive computer models assume an average workload throughout the dive. However, an unfit diver, for example, who is working hard at depth will breathe more heavily. Even fit divers sometimes find themselves working hard in situations such as swimming against a current or removing an anchor that is stuck under a rock. In such high workload circumstances the diver can absorb more nitrogen, particularly in the muscle tissue groups. This additional uptake of nitrogen, in turn, is exposing the diver to a greater risk of microbubble formation and the possibility of decompression sickness. With the Smart TRAK software that is supplied with the Smart COM, the sensitivity of the workload setting can be set by the diver according to their own level of fitness. The human body likes to maintain a core temperature of (37 C) 98 F and it has strategies such as shivering (involuntary muscle activity), to help maintain that temperature in cold situations. Diving in cold water causes vasoconstriction, i.e. a reduction of blood flow to arms and legs in favor of the main organs, in an attempt to conserve body heat. The skin is the tissue that is most affected by this. Vasoconstriction does not take place right away since the diver starts with a uniformly warm body. So, nitrogen absorption in the skin at first is normal. As the diver ascends and starts offgassing, vasoconstriction is now limiting the process. A diver can view the whole temperature profile of a dive with the Smart TRAK software and a Personal Computer. The Smart COM understands that different divers have different levels of fitness and different levels of exertion on different dives. The Smart COM can actually influence a diver who is working hard, to reduce the level of exertion, by relaxing and breathing more slowly. The Smart COM can do this because it is accurately monitoring the diver s rate of air consumption and changes in the rate of air consumption. If a diver persists in working hard at depth the Smart COM may ask the diver to complete an additional decompression stop. With Smart TRAK the sensitivity of the breathing rate warning is adjustable according to the diver s level of fitness. Earlier mathematical models assumed a mean workload output of 50W. With the ZH-L8 ADT MB model, even at level 0, if workload is increased to 85W then on a (15m) 50ft dive the ascent time is increased from 30 to 60 mins. So, diving in cold water makes the diver more susceptible to microbubble build up in the skin tissues and the possibility of skin bends. The Smart computer is constantly monitoring and displaying the ambient temperature and is considering the temperature in the calculation of the decompression schedule, with the objective of minimising skin bends. For example, in normal dives, the spinal tissue is usually considered as the first tissue to affect the decompression schedule. However, when it comes to diving in cold water the Smart considers that the skin is the most important tissue. As a consequence, for a diver in cold water, the Smart may suggest a shorter no-decompression schedule, or in the case of a decompression dive, longer decompression stops. On a cold water dive a fixed model advises a 28 minute ascent, whereas the ZH-L8 ADT MB advises a 48 minute ascent. On the second dive the skin tissues, which were the leading tissues at the end of dive 1, are already relatively cold at the beginning of the dive so they have a slower speed. Hence the smaller difference in total ascent time.

38 S M A R T M I C R O B U B B L E M A N A G E M E N T 6 Smart can provide a visual warning to the diver to take an advisory level stop and reduce microbubble formation. 6 microbubble suppression levels User adjustable microbubble suppression Integrates level stops and deco stops Total time to ascend includes level stop data Warns if level stop is ignored Cascading microbubble levels Surface warning of reduced microbubble suppression levels SMART REDUCES MICROBUBBLES The above table demonstrates what sort of level stop profiles can occur for a diver on the second of two "repetitive" dives. The first dive is to (30 m) 99 ft for 16 minutes and the second dive follows a surface interval of 1 hour and 49 minutes and is also for 99 feet and 16 minutes. To demonstrate the likely level stops a diver could expect for the 2nd dive, at various levels of microbubble suppression, UWATEC Engineers "dived" 6 UWATEC Smart Dive Computers with no suppression for the first dive, while computers 2 to 6 were set at the 5 different levels of microbubble suppression on the second dive. At level 0 the 6 minute stop at (3 m) 10 ft is actually a decompression stop, which is mandatory. While this is actually displayed separately on the UWATEC Smart Dive Computer's screen, for convenience we have included this 6 minute stop in the final stops in the above table. Cautions diver on high microbubble count Divers who have long term exposure to microbubbles risk soft tissue damage. Examples of soft tissue include the brain, spinal tissues and the retina. Divers who are at risk include professional divers such as instructors and dive masters who typically do a lot of repetitive diving. Sport divers who conduct multiple repetitive dives over the duration of a dive holiday are also at risk from microbubble build up. Experiments with deeper stops at the conclusion of a repetitive dive were proven to reduce microbubbles by up to 61% and in some cases eliminated microbubble formation. So, for example, if a diver has done three dives in one day, if on all dives the diver considered doing a series of deeper stops prior to the conclusion of the dives, microbubbles were substantially reduced. Microbubbles don t produce visible symptoms and they can only be measured with the aid of a detecting device. This hand held device generates an ultrasonic signal that strikes a microbubble in a diver s body to reflect back a distinct chirping sound. This is recorded and the recordings are then analyzed. The more chirps that can be heard on a recording, the greater the incidence of microbubbles in a diver. Post dive monitoring of 1058 dives observed detectable microbubbles in 37% of all the monitored dives and 67% of the repetitive dives. A Smart Dive Computer can be programmed to suppress the formation of microbubbles according to the diver s actual diving circumstances. The diver selects the level of suppression required for the particular dive. The Smart Dive Computer then assesses the likely microbubble build up from the previous dives and recommends an advisory deeper stop or level stop to be completed prior to the conclusion of the last dive. UWATEC set up two series (one week apart, with 9 volunteer divers) of three repetitive dives to (30 m) 99 ft for 16 minutes bottom time including 2 minutes 40 second descent with 75 minutes of surface interval. The second series included the following stops on the third dive: 12m 2 min; 9m 3min; 6m 5min; and 3m 6 min. The second series totally eliminated Very High and High Grade Microbubbles and significantly reduced Low Grade Microbubbles. As part of a major study DAN Europe Scanned divers from a substantial sample of 1058 dives within 30 minutes of each dive s conclusion. The participating divers were average open water divers, who conducted typical open water dives with a large range of depths and bottom times. DAN Europe discovered that in the case of repetitive dives 67% of all divers produced High Grade Microbubbles. This correlates with the DAN Diving Accident Reports of the last 15 years that show a relatively higher frequency of Decompression Illness after repetitive dives. Not only was there a higher incidence of microbubbles in repetitive dives, but there was a higher incidence of high bubble grade microbubbles - level 2 or higher on the Spencer Scale. A diver may manually select prior to the dive, 6 levels of suppression from level 0 where there is no suppression to level 5 where there is maximum suppression. Unlike decompression stops, which are compulsory, level stops are advisory. This is because the effects of microbubble formation are largely a long term condition, whereas decompression illness produces symptoms which require immediate treatment. If a diver ignores the recommended level stops by more than (1.5 m) 5 ft, the Smart cascades down to the next microbubble level. In comparing earlier fixed models with the ZH-L8 ADT MB model, even at level 0 the no decompression times for the first ascent are nearly identical, whereas for the following dives the total ascent times are greater by up to a factor of four.

39 S M A R T M I C R O B U B B L E M A N A G E M E N T 8 Smart constantly monitors and displays the CNS O 2 loading whether diving on air or any Nitrox mix up to 100% O 2. Smart TRAK allows the diver to store to a PC and analyse the dive history in the comfort of home, to extend the diving experience. Nitrox dive planner ppo 2 alarm CNS clock 75% alarm CNS clock 100% alarm Easy to change oxygen mix from 21% to 100% Smart TRAK replays actual screen data for the Smart COM and the Smart PRO in 4 seconds intervals. Oxygen mix percentage display Adjustable maximum ppo 2 CNS clock is adjusted by oxygen uptake according to workload NITROX Included Smart TRAK software indicates oxygen fraction at every point in the dive SMARTTRAK Nitrox allows divers to greatly extend bottom times and reduces the risk of decompression sickness. This is because Nitrox has a lower percentage of nitrogen than air. However, Nitrox has a higher percentage of oxygen, so it presents the sport diver with different risk factors. Oxygen is a very active molecule with the ability to burn the tissues in the Central Nervous System (CNS). These include the brain, spinal and other nerve tissues. The onset of problems from oxygen toxicity provide no warning, are immediate and can result in death. Smart dive computers monitor and warn on oxygen toxicity limits for both the accumulated CNS clock and the current partial pressure of oxygen. The results are displayed continuously and when 75% of the CNS toxicity limit is reached an acoustic alarm is sounded and the CNS% value display flashes. Should a diver reach 100%, then ascent must be commenced immediately. A Smart dive computer will also warn when the tolerable partial pressure of oxygen has been reached. Smart TRAK displays the ppo 2 limit as a black bar on the graph at the depth at which the ppo 2 limit is reached. In this instance for a 33% mix at 1.4 bar it is 105 ft (32 m). The Smart COM holds about 50 hours of dive data in its logbook and the Smart PRO holds about 100 hours. The key parameters of these dives can be retrieved and displayed on the respective Smart screens. For more detailed storage and analysis, Smart TRAK, which is supplied with Smart, can assist divers to store data that s limited only by the capacity of a PC s hard drive. With a Smart dive computer sampling rate of 4 seconds, this program allows divers to analyze their dives with amazing detail. Smart TRAK is an invaluable tool for the diver to analyze their behavior and further improve their diving technique. The complete dive profile is displayed, as are any attention messages or alarms. The software indicates the level of nitrogen saturation of the 8 body tissues that Smart monitors. If microbubble formation is estimated to have occurred, Smart TRAK also displays this. The actual Smart screen data that s displayed during a dive is also displayed on your PC screen with Smart TRAK. For the Smart COM user this includes the air consumption screen. Smart TRAK displays tissue saturation status throughout the dive. Ingassing tissues are shown in red, outgassing tissues are shown in green. Smart TRAK is a powerful database program that allows the diver to store useful information for later retrieval. Smart allows divers to program the oxygen mix from 21% O 2 (air) to 100% (pure oxygen) in 1% increments. The mix can be manually selected by the diver allowing different mixes to be dived with on any one day. A diver may also simulate a Nitrox dive with the Smart dive planner. With Smart TRAK software the Nitrox diver can change the maximum partial pressure of oxygen on both the Smart COM and the Smart PRO. For a diver who anticipates diving on the same nitrox mixture for a number of dives, with Smart TRAK it is possible to set the mixture reset to the default air (21% O 2 ) for an interval of up to 48 hours after a dive. Smart TRAK is a powerful database that allows divers to store and retrieve other useful information such as details about the dive location, conditions, weather and buddy details. With Smart TRAK the diver can change key parameters on the Smart PRO and the Smart COM.

40 S M A R T M I C R O B U B B L E M A N A G E M E N T 10 PRODUCT FEATURES AT A GLANCE Smart PRO Console Smart COM Smart PRO Wrist PROTECTIVE SCREEN SHIELD ILLUMINATED DISPLAY AUTO TURN ON/OFF ALL POSITION VIEW (APV) DISPLAY DISPLAYS TANK PRESSURE - BAR (PSI) USER ADJUSTABLE TANK RESERVE FOR RBT - CALCULATION USER ADJUSTABLE MICROBUBBLE SUPPRESSION AUTO ALTITUDE COMPENSATION 0-4,000M (13,000FT) ALTITUDE ADAPTATION TIME DISPLAYS ALTITUDE SECTOR PROHIBITED ALTITUDE ADVICE NITROX DIVE PLANNER DIVE DEPTH 0-120M (0-395FT) DISPLAY AMBIENT AND WATER TEMPERATURE DIVE TIME MAXIMUM DEPTH NO STOP TIME ADAPTIVE DECOMPRESSION MODEL B HLMANN ZH-L8 ADT MB REQUIRED DEEPEST DECO STOP (DEPTH) REQUIRED DEEPEST DECO STOP (TIME) INTEGRATES LEVEL STOPS AND DECO STOPS REMAINING DIVE TIME AT CURRENT DEPTH (RBT) USER ADJUSTABLE LOW AIR WARNING TOTAL TIME TO ASCEND INCLUDING DECO AND LEVEL STOP DATA VARIABLE ASCENT RATE 7-20M/MIN (23-67FT/MIN) NO STOP TIME IS LESS THAN 1 MINUTE ALARM RBT IS LESS THAN 3 MINUTES ALARM RBT LESS THAN 0 MINUTE ALARM HIGH BREATHING RATE ALARM (HIGH AIR CONSUMPTION) IGNORED DECOMPRESSION STOP ALARM WARNS IF LEVEL STOP IS IGNORED "CASCADING" MICROBUBBLE LEVELS ASCENT FASTER THAN 110% ALARM ASCENT FASTER THAN 140% ALARM ASCENT FASTER THAN 160% ALARM ASCENT FASTER THAN 180% ALARM PPO2 MAX HAS BEEN REACHED ALARM CNS 02 PERCENTAGE HAS REACHED 75% ALARM CNS 02 PERCENTAGE HAS REACHED 100% ALARM MISSED DECOMPRESSION STOP INSTRUCTIONS DISPLAYS ON THE SURFACE OF REDUCED MB-LEVEL DESATURATION TIME NO FLY ICON AND TIME SURFACE INTERVAL LOGBOOK CONTAINS 50 HOURS OF DIVING LOGBOOK CONTAINS 100 HOURS OF DIVING QUANTITY OF AIR USED MEASURES WATER TEMPERATURE CAUTIONS DIVER ON HIGH MICROBUBBLE LEVELS LONG LIFE BATTERY PERCENT OF REMAINING BATTERY LIFE USER SWITCHABLE METRIC/IMPERIAL USER ADJUSTABLE WORKLOAD WARNING EASY TO CHANGE OXYGEN MIX FROM 21% TO 100% OXYGEN MIX PERCENTAGE DISPLAY ADJUSTABLE MAXIMUM OXYGEN PARTIAL PRESSURE (PPO2) VIA SMARTTRAK CNS CLOCK IS ADJUSTED BY O2 UPTAKE ACCORDING TO WORKLOAD INCLUDED SMART TRAK SOFTWARE INDICATES O2 FRACTION ADJUSTABLE BACKLIGHT DURATION ADJUSTABLE DEPTH LIMIT ALARM VIA SMARTTRAK ADJUSTABLE PREMIX RESET VIA SMARTTRAK GAUGE MODE BUZZER SUPPRESSION IN SMART TRAK SMARTTRAK COMPATIBLE - CD INCLUDED INFRARED COMMUNICATION (IRDA) WITH SMARTTRAK

41

42 dpog = k.( p p dt dpog + k. pog dt Het opstellen van de ver- en ontzadigingsformules is de basisformule (wet van Haldane) is een lineaire differentiaalvergelijking in pog Om deze lineaire diff. vgl. op te lossen, stellen we eerst het rechter lid gelijk aan nul. dp dt dp p p og og og og ln( p waarbij C de integratiekonstante is door van bijde leden de exponnent te nemen We hebben nu een uitdrukking voor pog gevonden zodat we dp og kunnen bepalen. dpog k. t dt k. t dc dt = C. e.( k. ) + e. dt dt dt dpog k. t dc k. t = e k. C. e dt dt De diff. vgl. met rechter lid wordt dan: dpog + k. pog = k. p dt kt dc kt kt e k. Ce + k.( Ce ) = k. p dt dc kt = k. p. e dt bij overgang van ll naar rl verandert -kt in kt! + kp og = C. e og k. t k. t C = K. P. e. dt og = k. dt ) = k. p = 0 ) = k. t + C door te integreren vinden we de integratiekonstante C Deze integraal kunnen we niet zomaar oplossen; we moeten p kennen. Hiervoor stellen we twee oplossingen voor: A) p is een konstante zoals op de maximum diepte of of trapdiepte B) p is een lineaire funktie in de tijd ( p neemt lineair toe of af met een welbepaalde snelheid ) zoals tijdens het opstijgen of het dalen

43 A) p is een konstante in dit geval kunnen we p voor de integraal brengen C = K. P. e k. t. dt C = p. e kt + C1 er ontstaat opnieuw een integratie konstante die we nu C1 noemen Door de bekomen formule voor C in te vullen in de formule van pog en het zoeken van de randvoorwaarden kunnen we C1 vinden. pog = C.e -kt <=> pog = (p.e kt + C1).e -kt <=> pog = p + C1.e -kt randvoorwaarden: 1) op t = 0 is pog = po 2) op t = is pog = p 1) po = p + C1.e -k.0 <=> po = p + C1 <=> C1 = po - p 2) p = p + C1.e -k. <=> p = p + C1.0 <=> p = p uit randvoorwaarde 1 blijkt dat C1 = po - p zodat de formule voor pog wordt: pog = p + (po - p).e -kt of pog = p - (p - po).e -kt omdat po - p negatief is

44 dp V = B) p is een lineaire functie dt stel V de snelheid van drukverandering is de toename van druk met de tijd. V is niet 18 m/min maar 1.8 bar/min en indien we over de toename van de ppn2 spreken is V = 1.44 bar/min. Belangrijk is het teken van V indien de druk stijgt is dp positief en V dus ook (dalen). Bij het stijgen is dp negatief (de druk neemt af) en is ( voor een stijgsnelheid van 18 m/min ) V = bar/min! dp = V. dt p = V p = p Invullen in de formule voor C geeft: C = K. C = k. C = k. C = C = dt + V.( t 0 t 0 ) k. t P. e. dt k. t ( p0 + V.( t t0 )). e dt kt kt kt p0. e + V. t. d( e ) V. t0. e kt kt kt p0. e + [ V. e. t V. e dt] kt kt kt [ p0. e. dt + V. t. e dt V. t0. e dt] + C2 V. t + C2 kt V kt C = [ p0 + V.( t t0 )]. e. e + C2 k Door de bekomen formule in te vullen in de formule van pog en het zoeken van de randvoorwaarden, kunnen we de integratiekonstante C2 vinden. kt p = C. e og p p og og = = [ p + V.( t t )]. 0 kt [ p + V.( t t )] + C2. e e kt V k randvoorwaarde: 1) op t = to is pog = pogo V kt0 pogo = [ p0 + V.( t0 t0 )] + C2. e k V kt0 C2 = ( pogo p0 + ). e k de formule voor pog wordt dus: p p og og =. e kt V. e k kt 0. e. e [ p + V.( t t )] 0 = ( p 0 V k 0 ) + V.( t kt kt t + C2. e V k 0 kt + ( p ) + ( p ogo ogo p 0 p 0 V + ). e k V + ). e k k ( t t 0 k ( t t ) 0 )

45 An abridged version of this article was originally in DeepTech, 5:64; and the full version subsequently published in Cave Diving Group Newsletter, 121:2-5. The Importance of Deep Safety Stops: Rethinking Ascent Patterns From Decompression Dives by Richard L. Pyle Before I begin, let's make something perfectly clear: I am a fish-nerd (i.e., an ichthyologist). For the purposes of this commentary, that means two things. First, it means that I have spent a lot of time underwater. Second, although I am I biologist and understand quite a bit about animal physiology, I am not an expert in decompression physiology. Keep these two things in mind when you read what I have to say. Back before the concept of "technical diving" existed, I used to do more dives to depths of feet than I care to remember. Because of the tremendous sample size of dives, I eventually began to notice a few patterns. Quite frequently after these dives, I would feel some level of fatigue or malaise. It was clear that these post-dive symptoms had more to do with inert-gas loading than with physical exertion or thermal exposure, because the symptoms would generally be much more severe after spending less than an hour in the water for a 200-foot dive than they would after spending 4 to 6 hours at much shallower depths. The interesting thing was that these symptoms were not terribly consistent. Sometimes I hardly felt any symptoms at all. At other times I would be so sleepy after a dive that I would find it difficult to stay awake on the drive home. I tried to correlate the severity of symptoms with a wide variety of factors, such as the magnitude of the exposure, the amount of extra time I spent on the 10-foot decompression stop, the strength of the current, the clarity of the water, water temperature, how much sleep I had the night before, level of dehydration...you name it...but none of these obvious factors seemed to have anything to do with it. Finally I figured out what it was - fish! Yup, that's right...on dives when I collected fish, I had hardly any post-dive fatigue. On dives when I did not catch anything, the symptoms would tend to be quite strong. I was actually quite amazed by how consistent this correlation was. The problem, though, was that it didn't make any sense. Why would these symptoms have anything to do with catching fish? In fact, I would expect more severe symptoms after fish-collecting dives because my level of exertion while on the bottom during those dives tended to be greater (chasing fish isn't always easy). There was one other difference, though. You see, most fishes have a gas-filled internal organ called a "swimbladder" - basically a fish buoyancy compensator. If a fish is brought straight to the surface from 200 feet, its swimbladder would expand to about seven times its original size and crush the other organs. Because I generally wanted to keep the fishes I collected alive, I would need to stop at some point during the ascent and temporarily insert a hypodermic needle into their swimbladders, venting off the excess gas. Typically, the depth at which I needed to do this was much deeper than my first required decompression stop. For example, on an average 200-foot dive, my first decompression stop would usually be somewhere in the neighborhood of 50 feet, but the depth I needed to stop for the fish would be around 125 feet. So, whenever I collected fish, my ascent profile would include an extra 2-3 minute stop much deeper than my first "required" decompression stop. Unfortunately, this didn't make any sense either. When you think only in terms of dissolved gas tensions in blood and tissues (as virtually all decompression algorithms in use today do), you would expect more decompression problems with the included deep stops because more time is spent at a greater depth. As someone who tends to have more faith in what actually happens in the real world than what should happen according to the theoretical world, I decided to start including the deep stops on all of my decompression dives, whether or not I collected fish. Guess what? My symptoms of fatigue virtually disappeared altogether! It was nothing short of amazing! I mean I actually started getting some work done during the afternoons and evenings of days when I did a morning deep dive. I started telling people about my amazing discovery, but was invariably met with skepticism, and sometimes stern lectures from "experts" about how this must be wrong. "Obviously," they would tell me, "you should get out of deep water as quickly as possible to minimize additional gas loading." Not being a person who enjoys confrontation, I kept quiet about my practice of including these "deep decompression stops". As the years passed, I became more and more convinced of the value of these deep stops for reducing the probability of decompression sickness (DCS). In all cases where I had some sort of post-dive symptoms, ranging from fatigue to shoulder pain to quadriplegia in one case, it was on a dive where I omitted the deep decompression stops. As a scientist by profession, I feel a need to understand mechanisms underlying observed phenomena. Consequently, I was always bothered by the apparent paradox of my decompression profiles. Then I saw a presentation by Dr. David Yount at the 1989 meeting of the American Academy of Underwater Sciences (AAUS). For those of you who don't know who he is, Dr. Yount is a professor of physics at the University of Hawaii, and one of the creators of the "Varying- Permeability Model" (VPM) of decompression calculation. This model takes into account the presence of "micronuclei" (gas-phase bubbles in blood and tissues) and factors that cause these bubbles to grow or shrink during decompression. The upshot is that the VPM calls for initial decompression stops that are much deeper than those suggested by neo- Haldanian (i.e., "compartment-based") decompression models. It finally started to make sense to me. (For a good overview of the VPM, read Chapter 6 of Best Publishing's Hyperbaric Medicine and Physiology; Yount, 1988.) Importance of deep safety stops Richard Pyle 1

46 Since you already know I am not an expert in diving physiology, let me explain what I believe is going on in terms that educated divers should be able to understand. First, most readers should be aware that intravascular bubbles are routinely detected after the majority of dives - even "no decompression" dives. The bubbles are there - they just don't always lead to DCS symptoms. Now; most deep decompression dives conducted by "technical" divers (as opposed to commercial or military divers) are very-much sub- saturation dives. In other words, they have relatively short bottom-times (I would consider 2 hours at 300 feet a "short" bottom time in this context). Depending on the depth and duration of the dive, and the mixtures used, there is usually a relatively long ascent "stretch" (or "pull") between the bottom and the first decompression stop as calculated by any theoretical compartment-based model. The shorter the bottom time, the greater this ascent stretch is. Conventional mentality holds that you should "get the hell out of deep water" as quickly as possible to minimize additional gas loading. Many people even believe that you should use faster ascent rates during the deeper portions of the ascent. The point is, divers are routinely making ascents with relatively dramatic drops in ambient pressure in relatively short periods of time - just so they can "get the hell out of deep water". This, I believe, is where the problem is. Maybe it has to do with the time required for blood to pass all the way through a typical diver's circulatory system. Perhaps it has to do with tiny bubbles being formed as blood passes through valves in the heart, and growing large due to gas diffusion from the surrounding blood. Whatever the physiological basis, I believe that bubbles are being formed and/or are encouraged to grow in size during the initial non-stop ascent from depth. I've learned a lot about bubble physics over the last year, more than I want to relate here - I'll leave that for someone who really understands the subject. For now, suffice it to say that whether or not a bubble will shrink or grow depends on many complex factors, including the size of the bubble at any given moment. Smaller bubbles are more apt to shrink during decompression; larger bubbles are more apt to grow and possibly lead to DCS. Thus, to minimize the probability of DCS, it is important to keep the size of the bubbles small. Relatively rapid ascents from deep water to the first required decompression stop do not help to keep bubbles small! By slowing the initial ascent to the first decompression stop, (e.g., by the inclusion of one or more deep decompression stops), perhaps the bubbles are kept small enough that they continue to shrink during the remainder of the decompression stops. If there is any truth to this, I suspect that the enormous variability in incidence of DCS has more to do with the pattern of ascent from the bottom to the first decompression stop, than it has to do with the remainder of the decompression profile. DCS is an extraordinarily complex phenomenon - more complex than even the most advanced diving physiologists have been able to elucidate. The unfortunate thing is that we will likely never understand it entirely, largely because our bodies are incredibly chaotic environments, and that level of chaos will hinder any attempts to make predictions about how to avoid DCS. But I think that we, as sub-saturation decompression divers, can significantly reduce the probability of getting bent if we alter the way we make our initial ascent from depth. Some of you may now be thinking "But he said he's not an expert in diving physiology - why should I believe him?" If you are thinking this, then good - that's exactly what I want you to think because you shouldn't trust just me. So, why don't you dig up your September '95 issue of DeepTech (Issue 3) and read Bruce Weinke's article? I know it covers some pretty sophisticated stuff, but you should keep re- reading it until you do understand it. Why don't you call up aquacorps and order audio tape number 9 ("Bubble Decompression Strategies") from the tek.95 conference, and listen to Eric Maiken explain a few things about gas physics that you probably didn't know before. While you're at it, why don't you order the audio tape from the "Understanding Trimix Tables" session at the recent tek.96 conference? You can listen to Andre Galerne (arguably the "father of trimix") talk about how the incidence of DCS was reduced dramatically when they included an extra deep decompression stop over and above what was required by the tables. On the same tape you can listen to Jean-Pierre Imbert of COMEX (the French commercial diving operation which conducts some of the world's deepest dives) talk about a whole new way of looking at decompression profiles which includes initial stops that are much deeper than what most tables call for. Why don't you ask George Irvine what he meant when he said he includes "three or four short deep stops into the plan prior to using the first stop recommended by each of the [decompression] programs" in the January, '96 issue of DeepTech (Issue 4)? If that's not enough, then check out Dr. Peter Bennett's editorial in the January/February 1996 Alert Diver magazine; he's talking about basically the same thing in the context of recreational diving. If you really want to read an eye-opening article, see if you can find the report on the habits of diving fishermen in the Torres Strait by LeMessurier and Hills (listed in the References section at the end of this article). The lists goes on and on. The point is, I don't seem to be the only one advocating deep decompression stops. Are you still skeptical? Let me ask you this: Do you believe that so-called "safety stops" after so-called "nodecompression" dives are useful in reducing probability of DCI? If not, then you should take a look at the statistics compiled by Diver's Alert Network. If so, then you are already doing "deep stops" on your "no-decompression" dives. If it makes you feel better, then call the extra deep decompression stops "deep safety stops" which you do before you ascend to your first "required" decompression stop. Think about it this way: Your first "required" decompression stop is functionally equivalent to the surface on a dive that is taken to the absolute maximum limit of the "no-decompression" bottom time. Wouldn't you think that "safety stops" on "no-decompression" dives would be most important after a dive made all the way to the "no- decompression" limit? Some of you may be thinking, "I already make safety stops on my decompression dives - I always stop 10 or 20 feet deeper than my first required stop." While this is a step in the right direction, it is not what I am talking about here. "Why not?", you ask, "I do my safety stops on no-decompression dives at 20 feet. Why shouldn't I do my deep safety stops 20 feet below my first required ceiling?" I'll tell you why - because the safety stops have to do with preventing bubble growth, and bubble growth is in part a function of a change in ambient pressure, not a function of linear feet. Suppose that, after a dive to 75 feet, you make a safety stop at 20 feet. Well, the ambient pressure at sea level is 1 ATA. The ambient pressure at 75 feet is about 3.3 ATA. The ambient pressure at your 20-foot safety stop is 1.6 ATA - which Importance of deep safety stops Richard Pyle 2

47 represents roughly the midpoint in pressure between 3.3 ATA and 1 ATA. Now, suppose you're on a dive to 200 feet (about 7 ATA) and your first required decompression stop is 50 feet (about 2.5 ATA). The ambient pressure midpoint between these two depths is 4.75 ATA, or a little less than 125 feet. Thus, on this dive you would want to make your deep safety stop at about 125 feet - exactly the depth I used to stop to stick a hypodermic needle in my little fishies. But of course, the physics and physiology are much more complex than this. It may be that ambient pressure mid- points are not the ideal depth for safety-stops - in fact, I can tell you with near certainty that they are not. From what I understand of bubble-based decompression models, initial decompression stops should be a function of absolute ambient pressure changes, rather than proportional ambient pressure changes, and thus should be even deeper than the ambient pressure mid-point for most of our decompression dives. Unfortunately, I seriously doubt that decompression computers will begin incorporating bubble-based decompression algorithms, at least not in their complete form. Until then, we decompression divers need a simpler method - a rule of thumb to follow that doesn't require the processing power of an electronic computer. Perhaps the ideal method would be simply to slow down the ascent rate during the deep portion of the ascent. Unfortunately, this is rather difficult to do - especially in open water. Instead, I think you should include one or more discrete, short-duration stops to break up those long ascents. Whether or not it is physiologically correct, you should think of them as pit-stops to allow your body to "catch up" with the changing ambient pressure. Here is my method for incorporating deep safety stops: 1) Calculate a decompression profile for the dive you wish to do, using whatever software you normally use. 2) Take the distance between the bottom portion of the dive (at the time you begin your ascent) and the first "required" decompression stop, and find the midpoint. You can use the ambient pressure midpoint if you want, but for most dives in the "technical" diving range, the linear distance midpoint will be close enough and is easier to calculate. This depth will be your first deep safety stop, and the stop should be about 2-3 minutes in duration. 3) Re-calculate the decompression profile by including the deep safety stop in the profile (most software will allow for multi-level profile calculations). 4) If the distance between your first deep safety stop and your first "required" stop is greater than 30 feet, then add a second deep safety stop at the midpoint between the first deep safety stop and the first required stop. 5) Repeat as necessary until there is less than 30 feet between your last deep safety stop and the first required safety stop. For example, suppose you want to do a trimix dive to 300 feet, and your desktop software says that your first "required" decompression stop is 100 feet. You should recalculate the profile by adding short (2-minute) stops at 200 feet, 150 feet, and 125 feet. Of course, since your computer software assumes that you are still on-gassing during these stops, the rest of the calculated decompression time will be slightly longer than it would have been if you did not include the stops. However, in my experience and apparently in the experience of many others, the reduction in probability of DCI will far outweigh the costs of doing the extra hang time. In fact, I'd be willing to wager that the advantages of deep safety stops are so large that you could actually reduce the total decompression time (by doing shorter shallow stops) and still have a lower probability of getting bent - but until someone can provide more evidence to support that contention, you should definitely play it safe and do the extra decompression time. One final point. As anyone who reads my posts on the internet diving forums already knows, I am a strong advocate of personal responsibility in diving. If you choose to follow my suggestions and include deep safety stops on your decompression dives, then that's swell. If you decide to continue following your computer-generated decompression profiles, that's fine too. But whatever you do, you are completely and entirely responsible for whatever happens to you underwater! You are a terrestrial mammal for crying out loud - you have no business going underwater in the first place. If you cannot accept the responsibility, then stay out of the water. If you get bent after a dive on which you have included deep safety stops by my suggested method, then it was your own fault for being stupid enough to listen to decompression advice from a fish nerd! References: Bennett, P.B Rate of ascent revisited. Alert Diver, January/February 1996: 2. Hamilton, B. and G. Irvine A hard look at decompression software. DeepTech, No. 4 (January 1996): LeMessurier, D.H. and B.A. Hills Decompression sickness: A thermodynamic approach arising from a study of Torres Strait diving techniques. Scientific Results of Marine Biological Research. Nr. 48: Essays in Marine Physiology, OSLO Universitetsforlaget: Weinke, B The reduced gradient bubble model and phase mechanics. DeepTech, No. 3 (September 1995): Yount, D.E Chapter 6. Theoretical considerations of Safe Decompression. In: Hyperbaric Medicine and Physiology (Y-C Lin and A.K.C. Niu, eds.), Best Publishing Co., San Pedro, pp I would like to thank Eric Maiken for explaining bubble physics to me and for adding some theoretical foundation to my silly ideas. Palau 'Twilight Zone' Expedition BISHOP MUSEUM Importance of deep safety stops Richard Pyle 3

48 Decompression theory - Bubble models ABSTRACT This page describes principles and theories about bubble generation and bubble growth in the scuba divers body and about the effect of bubble formation on decompression and decompression sickness (DCS, bends) in scuba diving. Whereas classical (neo-)haldane theories are mainly empirical and only take dissolved gas into account, bubble theories intend to give a physical explanation of the effects of bubbles on decompression. Bubble theories take dissolved and free gas into account. Especially the Varying Permeability Model (VPM) and Reduced Gradient Bubble Model (RGBM) give good explanation. History In classic decompression theory according to Haldane and successors a certain amount of supersaturation of the divers tissue with dissolved inert gas is allowed. The divers tissue is divided in a number of hypothetical tissue compartments. A certain limit (M-value) is associated with each compartment to supersaturation levels of dissolved inert gas in the compartment (tissue tension). This theory suggests efficient decompression by pulling the diver as close to the surface as possible with constraint that in all tissue compartments the supersaturated tissue tension remains within the limits. By pulling the diver as close to the surface the pressure gradient between the supersaturated tissue tension and the pulmonary (or arterial) gas is maximized. This enhances the elimination of the excess gas in the tissue. This theory is mainly empirical and based on experiment. At the moment most diving tables and computers are based on this theory. Since the early days, diving has become more sophisticated by diving deeper and longer, the use of other breathing mixtures, etc. Some tech divers have made their own adaptations to the decompression schedules by inserting depression stops at greater depth ('deep stops', sometimes called 'Pyle stops' after Richard Pyle). These divers report feeling better when using these deep stops. This suggests that classic decompression theory fails in some situations and cannot be extrapolated to every diving situation. In order to gain insight in the principles of decompression, forming of bubbles during decompression has been studied for the last three decades. This has resulted in new theories like the Varying Permeability Model (VPM) by Yount et al. and the Reduced Gradient Bubble Model (RGBM). Bubble theories do not only take into account the dissolved gas (like the Haldane models), but also the free gas in the divers body. In this chapter we will have a look at some features of bubble theory. Lots of mathematics will be presented. The most important equations however, will be highlighted. Bubbles and surface tension Consider a small air bubble in a glass of water. For the moment we neglect the solubility of the air in water. The small amount of air within the bubble is surrounded by a surface. The surface consists of water molecules which are unbound to one side. An unbound molecule represents more energy than a molecule which is completely surrounded by other water molecules. A surface tension γ is associated with this surface between air and water. The surface tension is the amount of energy per unit of surface area and is expressed in J/m 2 or N/m. A system will always try to minimize energy. Surface tension tends to minimise the bubble's surface. Hence, a bubble tends to collapse. However, collapsing a bubble decreases its volume. This will increase the gas pressure in the bubble (Boyle's law), until equilibrium is established: the internal pressure compensates the surface tension. The internal pressure due to the ambient pressure and surface tension is given by the Laplace equation: Figure 1: In equilibrium the internal pressure in the bubble is equal to the sum of the ambient pressure and the skin pressure due to the surface tension Decompression Theory Bubble models David E. Yount Deep Ocean 1

49 P in = P amb + P surf = P amb + 2γ/r (1) r Radius of the bubble in m γ Surface tension in joule/m 2 of N/m. The surface tension of water at 273 K is N/m. P in Pressure inside the bubble in N/m 2 =10-5 bar P amb Ambient pressure in N/m 2 =10-5 bar P surf Pressure due to the surface tension in N/m 2 =10-5 bar From this equation we learn that the smaller the bubble, the higher the pressure inside. You can experience the radius dependency of the pressure by trying to blow a balloon (bubble principles perfectly apply to a balloon up to the point where the balloon explodes). To get the first blow of air into the balloon (small radius) is a hell of a job, whereas it becomes easier if the balloon becomes larger. Bubbles and diffusion When we have a bottle of beer things get a bit more complicated (Usually the opposite holds, but when we look at the bubbles it might be). Bubbles in beer contain Carbon Dioxide. There is also Carbon Dioxide in solution in the beer. Carbon Dioxide can diffuse from the solution into the bubble or vice versa, depending on the partial pressure of the Carbon Dioxide in solution and in the bubble. If we assume that the bubble consist of only Carbon Dioxide, the Carbon Dioxide pressure in the bubble is given by equation (1) and depends on the radius of the bubble. We define the partial pressure of the Carbon Dioxide in solution in the beer to be P t. (If we regard the bottle of beer as a primitive model for a diver, we could call it 'tissue tension'). If the bottle is closed, the partial pressure of the Carbon Dioxide in solution P t is in equilibrium with the ambient pressure P amb. If we assume there is only Carbon Dioxide gas in the (closed) beer bottle, the beer is saturated with Carbon Dioxide and P t will be equal to P amb (we can neglect hydrostatic pressure). The pressure in the bubble P in will be higher than P t due to the surface tension. Gas from within the bubble will diffuse into solution and the bubble will collapse. So every bubble will collapse eventually due to this gradient P in -P t. This is why in a closed bottle of beer there are no bubbles and there is no foam. However, if we open the bottle things will be different. The ambient pressure will drop, whereas the value of P t remains the same, at least for the moment. In this case P t is larger than P amb : the beer is supersaturated with Carbon Dioxide. Given an ambient pressure P amb and the partial pressure P t of the Carbon Dioxide in solution, there is a critical bubble radius r min at which the pressure inside the bubble P in equals P t. The critical radius can be found by substituting P in by P t in equation (1): r min = 2γ/(P t - P amb ) (2) For bubbles which size exceeds this critical size the pressure P in in the bubble is smaller than the partial pressure P t of the Carbon Dioxide in solution. Carbon Dioxide will diffuse from solution into the bubble. The bubble will grow. For bubbles smaller than the critical size, the opposite holds: gas from the bubble diffuses into solution and the bubble shrinks until it collapses completely. Bubbles at the critical size are in equilibrium, though it is an unstable equilibrium. This is depicted in Fig. 2. Figure 2: So every bubble with a radius larger than r min will start to grow. When we look at our opened bottle of beer we see bubbles becoming visible and heading for the surface, where they form foam. If you scrutinize a bubble you'll see that it grows during ascent. Its diameter might have doubled or tripled when it arrives at the surface. You might think this is due to Boyle's law. However it takes an ascent of several meters for a bubble to double its diameter. The growth of the bubble is due to the diffusion described above. As an example, we can calculate critical radii for Spa Barisart Soda ( g/l Carbon Dioxide). The pressure in the bottle specified by Spa is shown in next table (dependant on temperature). The partial pressure P t of the Carbon Dioxide Decompression Theory Bubble models David E. Yount Deep Ocean 2

50 in solution is roughly that value. If we open the bottle the ambient pressure P amb drops to 1 bar, whereas the partial pressure P t remains at the high value. Using equation (2) we can calculate the critical radius r min. Temperature Pressure (bar=10 5 ( C) Pa) r min (µm) The Varying Permeability Model According to previous chapter, in a supersaturated situation any bubble exceeding a critical size r min will grow (and will disappear by floating to the surface) and any bubble smaller than this size will collapse. In a normal non-supersaturated situation, r min approaches infinity. Any bubble will collapse. So we do not expect any bubbles around after a while. You might expect that if no initial bubbles are around, there is no bubble to grow on supersaturating the liquid. The tensile strength of water is estimated on 1000 atm, making immense supersaturations possible, before bubbles (voids) are created. If no initial bubbles would be present in the water making up the diver, a diver could easily dive to a kilometer depth and pop up to the surface without any problems. In practice, this is not the case. Bubbles form on modest decompression as low as 1 atm. Here comes in the Varying Permeability Model (VPM). The VPM was initially defined by Yount et al. [2] in order to give a quantitative explanation on the formation of bubbles in decompressed gelatin [1] (as model for divers tissue). Later on, they showed this model can be used to calculate dive tables as well [3], [4]. In next paragraphs we will have a look at the gelatin theory. Later on we will apply the theory to diving. The gelatin experiments Figure 3: Skins of varying permeability are the base of the VPM Experiments on gelatin have been performed, by David Yount and other researchers [1]. The advantage of gelatin over water is that any bubble appearing during decompression gets trapped and won't flow to the surface. In this way they can be observed and counted. Yount applied the rudimentary pressure of Figure 4 to gelatin samples: Gelatin samples were made at ambient pressure P amb =P 0 of 1 atm. The samples were rapidly compressed in a 100% Nitrogen atmosphere to P amb =P m. The samples were left at a pressure P amb =P s =P m for more than 5 hours. This period was long enough to fully saturate the sample at this pressure, so that P t =P s. After this, the samples were rapidly decompressed to a final pressure P amb =P f. After this decompression, bubbles formed in the sample. The number of bubbles were counted. Pressure changes are regarded fast: during the changes no gas is taken up or removed from any bubble. Figure 4: Rudimentary pressure schedule applied to the gelatin samples by Yount. Decompression Theory Bubble models David E. Yount Deep Ocean 3

51 Basic concepts Figure 5: Pressures acting on the surface of the bubble. According to the VPM, in aqeous media like water and gelatin stable gaseous cavities are present. They are called nuclei. Radii range from a few 1/100 µm up to around 1 µm. Any nucleus in water larger will flow to the surface and disappear. Whereas an ordinary bubble with these radii would collapse under normal conditions (no supersaturation), these nuclei appear to be exceptionally stable and have a long life. Yount proposed this stability is due to an elastic skin made up of surfactant, as shown schematically in Figure 3. Surfactant consists of (hydrophobic) surface active molecules, which are aligned. During the compression stage, these skins are permeable for gas up to a pressure of around 8 atm. Diffusion through the skin takes place. The pressure P in of the gas in the nucleus is equal to the dissolved gas tension P t in the surrounding liquid. Above this pressure, the skin becomes impermeable. Upon decompressing (reducing the ambient pressure) the skins are regarded permeable. The skin gives rise to a 'surface compression' Γ which opposes the regular surface tension γ of the water/air surface, as shown in Figure 5: P in + 2Γ/r = P amb + 2γ/r (3) The skin tension Γ is not constant but ranges from 0 to a maximum γ c, which is called the 'crumbling compression'. The idea is that small variations of the size of the nucleus can be supported by varying the distance between the molecules in the skin. This gives rise to varying Γ. This situation is described by equation (3) and is referred to as the small-scale situation. In this equilibrium situation and in the permeable region, due to diffusion the internal pressure P in is equal to the tension P t. In the samples (no hydrostatic pressure, 100% Nitrogen) P t equals P amb. So P in = P t = P amb. In this situation Γ equals γ, according to equation (3). Upon compressing and decompressing, variation of the size of the nucleus becomes to large to be supported by varying distances between molecules. Surfactant molecules have to be expelled from or taken up into the skin in order to compensate for the area decrease resp. increase of the nucleus. This is schematically shown in Figure 6. The skin is surrounded by an amount of surfactant, which is not part of the skin. This amount acts as a reservoir, taking up or supplying surfactant molecules from or to the skin. The reservoir molecules are not aligned and cannot support a pressure gradient. Γ takes its crumbling value γ c in this large-scale situation. Yount proposes two derivations of the VPM [2]: one from a thermodynamic point of view and one from a mechanical point of view. Figure 6: The large-scale situation: variation in the size of the nucleus result in expelling molecules from the skin In the original sample there is a initial distribution of nuclei with radii distributed according to some function f(r 0 ). (The '0' in r 0 refers to the initial situation). On applying the pressure schedule, it is assumed that all nuclei with a radius larger than some minimal initial radius r 0 min will grow into bubbles. The number of bubbles N that occur is given by the integration of f(r 0 ) from r 0 min to infinity. N = f(r 0 ) dr 0, integration from r 0 min to (4) Applying this theory to a diver, it might be assumed that the severity of Decompression Sickness (DCS) might be related to this number of bubbles, which occur after decompression. Hence, r 0 min becomes an indication for the severity of DCS. It is assumed that no nuclei are extinguished or created during application of the pressure schedule. Furthermore it is assumed that the ordering of nuclei is preserved: if one nucleus is larger than an other one, this is still true after a pressure change (ordering hypothesis). At the end of the pressure schedule there is a new distribution of radii g(r f ) and a new radius r f min above which all nuclei will grow into bubbles. Note: a nucleus with radius r 0 min ends up as a nucleus with radius r f min after application of the presure schedule. The aim of next VPM calculations is Decompression Theory Bubble models David E. Yount Deep Ocean 4