15 March 1983 ERRATUM

Transcription

1 DEPARTMENT OF THE NAVY NAVY EXPERIMENTAL DIVING UNIT PANAMA ITY, FLORIDA Marh 1983 ERRATUM NEDU Report 1-83: omputer Algorithms Used in omputing the MK 15/16 onstant 0.7 ATA Oxygen Partial Pressure Deompression Tables. After publiation and distribution, an error was found in Version 1.1 of Subroutine FRSP7 whih will ause small underestimates in no-deompression time and whih will (in ertain instanes) ompute first stop depths one depth inrement deeper than neessary. (The program omputes 0 min stop times at these too deep first stops so the resulting deompression profiles are orret). All holders of the above report should make the following hanges and substitutions to the original: 1. Replae pages 40/41 and B4-1 thru B4-4 (Annex B4) with the attahed pages. Note that the replaement pages are all oded in the lower right hand orner. Subroutine FRSP7 is now Version Make a pen and ink hange to Fig. 9 (page 30). hange the no-deompression time at 110 FSW from 23 to 24 min. All other deompression profiles and Model Parameter Printouts remain orret for Version 1.2 of Subroutine FRSP7.

2 Exponential Update Proedure (Lines ) This proedure updates the tissue for a linear asent or desent. After the update is omplete, ontrol is transferred bak to the beginning of the loop until all NTISS tissues have been done. After all tissues have been updated, ontrol drops through to the proedure whih omputes the Instantaneous Asent Depth. Instantaneous Asent Depth omputation Proedure (Lines ) This proedure is idential to the one used in the E-L Version of UPDT7. Subroutine FRSP7 This subroutine finds the depth of the first stop for a speified asent rate. The depth of the first stop is passed bak to the main program as an argument of the subroutine (DFS), all other data is passed in the three ommon bloks PARAM, BLDVL and MDATA. The subroutine uses the Instantaneous Asent Depth (IAD) alulated by Subroutine UPDT7 as a first approximation of the first stop depth. A trial update at the speified rate is performed first to DIN deeper than the IAD then if all asent riteria are met at DIN+IAD to TAB itself. Depending on the rate of asent and the initial tissue tensions the tissues may saturate or desaturate during the trial asent and may have taken up exess gas (in whih ase the new IAD after asent will have inreased), offgassed suffiiently to go shallower (in whih ase the new IAD will have dereased) or still have just enough gas on board to require a stop at IAD (in whih ase the IAD will not have hanged). Depending on whether the IAD has inreased or dereased after the trial asent, the first stop depth estimate is inreased or dereased in inrements of the stop depth inrement (DIN) until the TAD before and after asent are the same and are in fat equal to the depth whih has just been asended to. Initialization Proedure (Lines ) The depth of the first stop (DFS) is initially set to the urrent depth and if the urrent depth is equal to or shallower than the IAD, DEPTH beomes the first stop depth. This preaution is neessary for two reasons. The first is that if the DX option is used for an asent one ould end up at a depth shallower than the IAD. If the DX option were not speified for the next asent, the subroutine would attempt to desend to the IAD ausing a negative desent time to be omputed. Rather than have that happen, a stop will simply be taken at DEPTH until asent is possible. The seond situation will our if a 0 min stop is taken at a deompression stop during asent (as in hanging breathing gases) in whih ase the urrent depth will be equal to the IAD. In this ase (unless preautions are taken) a trial

3 desent would be performed to DIN+IAD ausing the tissue tensions to inrease and an anomalous stop to be taken at DIN+IAD. In the auto-deompression mode one an never go too shallow so the depth of the first stop will never be deeper than the urrent depth. Line 110 ensures this is always the ase. In lines 115 to 118 the logial variable LASTIT is initialized to "false" and the urrent tissue tensions and IAD stored temporarily beause they will be hanged when Subroutine UPDT7 is alled to do the trial asent. Depth of First Stop Iteration Loop (Lines ) The variable MIND is set initially to the IAD and in lines a trial update is done from the urrent depth to MIND+DIN. This must be done beause the definitions of the asent riteria requires that they be met DIN deeper than a given depth before asent to that depth is possible. In lines 144 and 145 the tissue tensions and TAD are restored to their original values. If after asent to MIND+DIN the IAD has inreased, ontrol is transferred by line 152 to line 161 where it will drop through to line 173. If the IAD has remained the same or dereased during the first trial asent lines do another trial asent to IAD. If the new IAD equals MIND (the value of IAD before asent) then line 161 transfers ontrol to Statement 50 (line 188) where the value of the depth of the first stop (DFS) is set to MIND and the subroutine exited. If IAD and MIND are not equal after the trial asent then ontrol goes to line 173. Sine additional tissue saturation or desaturation takes plae during asent it is unlikely that MIND and IAD will be equal the first time through the loop. The usual sequene of events is that the value of MIND is systematially inreased or dereased and by the seond iteration the value of IAD doesn't hange after the trial update and the loop is exited at line 161 with MIND ontaining the value of the depth of the first stop. In a very few ases, however, the IAD may inrease on one pass through the loop and derease on the next. This ours when a tissue is still saturating during asent. On the first trial update all tissue tensions will be less than their maximum permissible values ontained in array M and the new IAD dereases by one depth inrement after the trial update to the original value of TAD. The next time through the loop the trial update will be to the new value of IAD. If a tissue was saturating during asent it may have taken up enough additional gas during the additional asent to the new IAD to just exeed its maximum permissible value. Thus, when the next trial update is done the value of IAD will derease by one depth inrement. This osillation will ontinue indefinitely beause the tissue will have a tension just below its maximum permissible value at the deeper trial stop and just above it at the shallower trial stop. Sine the asent riteria state that one the maximum permissible tissue tension has been reahed at a given depth that asent to the next shallower depth inrement is allowed the depth of the first stop is taken at the shallower of the two depths, and assigned to MIND. One the depth of the first stop has been found the IAD is restored to its original value, the value of the integer MIND is assigned to the real variable DFS and the subroutine returns ontrol to the main program (lines ). 4 1

4 8.FRSP7 T=00004 IS ON R00012 USING BLKS R=0OOO SUBROUTINE FRSP7DFS ), 01 MAR 93 VER 1. 2 FINDS DEPTH OF FIRST STOP (DFS). TRIAL STOP DEPTH <MIND> INITIALLY SET TO URRENT INSTANTANEOUS ASENT DEPTH ( IftD). A TRIAL ASENT TO "MIND" IS DONE TO SEE IF "IAD" HANGES DURING ASENT. IF "IADn HANGES A NEU TRIAL ASENT FROM "DEPTH1' TO THE NEW "IftDn IS DONE, ITERATION ONTINUES UNTIL THE "IAD" AFTER rts.ent AND "MIND" ARE EQUAL, DEPTH OF FIRST STOP WILL NEVER BE DEEPER THAN THE URRENT DEPTH, IF ASENTS ftluoys rtompanied BY APPROPRIATE DEOMPRESSION NO FRO6LEtlS UILL OUR. HOWEVER, IF AN &ENT IS TAKEN UITHOUT DEOMPRESSION STOPS THEN A FIRST STOP DEPTH SOUGHT, THE "IAD" MAY BE DEEPER THAN THE URPEMT DEPTH. IN THESE ASES THE FIRST STOP DEPTH UILL BE THE URRENT DR EDURRD D. THALMftNN < M> U.S. NAVY EXPERIMENTAL DIVING I? I- ************** * VARIABLES * ** *rf(********* ftmblso2 DEPTH F GPO2 D DFS D I t4 FN2 HLFTM I AD I ADTMP LASTIT N MIND NTISS P PflO2 PBOVP PHs0 PO2 AMBIENT-ARTERIAL OXYGEN GRADIENT <FSM> URRENT. DEPTH <FSW OR MSU> METRI ONVERSION FATOR ONSTANT PARTIAL PRESSSURE 02? DEPTH HftNGE < FSW OR MSW Â DEPTH OF FIRST STOP (FSW OR MSU) STOP DEPTH INREMENTS <FSW OR MSU) INERT GAS FRATION OMPARTMENT HrtLFTIMES <MIH > INSTANTANEOUS ASENT DEPTH <FSW OR!'ISM? VARIABLE TO TEMORARILY STORE URRENT VALUE OF "IAD". LAST TIME THROUGH ITERATION LOOP? ONPftRTMENT MAXIMUM GAS TENSION HRPAY <FSW> TRIAL FIRST STOP DEPTH <FSM OR HSW) NUMBER OF HrtLFTIME OMPARTMENTS < 9 MAX. > OMPARTMENT GAS TENSION ARRAY < FSM > ARTERIAL O2 PARTIAL PRESSURE <FSW> GAS PHASE OVERPRESSURE < FSU > PARTIAL PRESSURE OF WATER VAPOR <FSW> INSPIRED OXYGEN PARTIAL PRESSURE ATA > B4-1

5 PV02 VENOUS 1202 PARTIAL PRESSURE <FSU;> PV02 VEI-fOUS 02 PARTIAL PRESSURE <FSW5 RATE RATE OFTRA'JEL DURING DEPTH HANGE <FSW OR MSI.i!/NIN> SDR SATURATION-DESATURATION HrtLFTIME RATIO T TIME HANGE DURING ASENT <MIN) TP ARRAY TO TEMPORARILY STORE OMPARTMENT GAS TEHSIONS NOTE: FOR PARTIAL PRESSURES WHIH ARE IN FSW. 33 FSWs1 ATA. ###########*######################################################*#### ################################################*#*#################### ******'**** ************** * SUBROUTINES REQUIRED *... UPDT7 UPDATES MODEL OVER ft SINGLE TIME INTERVAL È#############################à #à #################################*# MOREL INPUT VARIABLES THESE ARE THE ONLY VARIABLES SENT FROM THE MAIN PROGRAM TOTHE MODEL SUBROUTINES, THIS OMMON STATEMENT MUST HPPEftR IN ALL MODEL SUBROUTINES, OMMIN,'MDATA/ T. D, DEPTH, RATE, PO2, FN2, P02, DINE F MODEL OMNOM THESE VARIABLES ARE.SEtfT BETWEEN MODEL SUBROUTINES ONLY. THESE OMMON STATEMENTS MUST QPPEAR IN ALL MODEL SUBROUTItiES. OPlMON,'PARAM/M<9,30),P<9),HLFTM<9>,NTISS,SDR<9), OMMON,'BLDVL/PAO2,PH20, PV02, PV02, rtmba02, PBOVP LOGIAL P02,LASTIT REAL M DIMENSION TP<9> w******:**************************************************************** INITIALIZATION PROEDURE *********************************************************************** 0106 INITIALIZE DEPTH OFFIRST STOP TO URRENT DEPTH. IF "DEPTH" EQUAL 0107 TO OR SHALLOUER THAN "IfiD" FIRST STOP IS AT "DEPTH" DFS=DEPTH IF< INT<DEPTH).LE. IAD) RETURN INITIALIZE "LAST ITERATION" SWITH. SAVE TISSUE TENSIONS AND "IAD" TEMPORARILY. IAD

6 *********************************************************************** END OFIHITIALIZATION *********************************************************************** *********************************************************************** DEPTH OF FIRST STOP ITERATION LOOP ALL EXITS GO TO STATEMENT #50 *********************************************************************** TRY FIRST STOP DEPTH AS "IAD". DEFINITION OF ASENT RITERIA REQUIRES THEY BE MET "DIN" DEEPER THAN FINAL FIRST STOP DEPTH. SUBROUTINE UPDT7 WILL OMPUTE NEW "IAD" AFTER TRIAL ASENT. REESTABLISH TISSUE TENSIONS AFTER ALLING SUBROUTINE UPDT7, ALL IJPDT7 DO 32 I=l,NTISS P< I?=TP< I ) IF "IAD" HASN'T HANGED OR HAS DEREASED DURING TRIAL ASEHT TO "MIND+DItl" THEM ASENT TO "NIND" MAY BE POSSIBLE WITHOUT VIOLATING THE ASEHT RITERIA* GIVE IT A TRY, REESTABLISH TISSUE TEHSIOHS UHEH DONE. IF< IAD.GT. MIND m 0 TO 42 D-MIND-DEPTH TODXRATE ALL UPDT7 DO 40 I=l,NTISS P< I >=TP< I 5 IF NElJ "IAD" AND "WIND" EQUAL AFTER TRIAL ASENT, WE'RE DONE. IF NEU "IAD" IS SHALLOWER THAN "MIND" SET "LASTIT" TO TRUE. THIS UILL STOP THE ITERQTION IF "IAD" BEOMES GREATER THAN "MIND" THE NEXT TIME AROUND. THIS UILL PREVENT GETTING STUK IN THE LOOP IF THERE IS A TISSUE STILL SATURATING AT "MIND" IN WHIH ASE "IAD" UILL NEVER EQUAL "NIt4D" BUT MILL OSILLATE ONE DEPTH INREMENT DEEPER AND SHALLOUER ON SUESSIVE ITERATIONS, IN THESE ASES THE FIRST STOP DEPTH IS THE FIRST VALUE OF "NIND" UHIH AUSES "IAD" 70 INREASE IN VALUE AFTER IT HAD DEREASED ON THE PREVIOUS ITERATION. IF< IAO.LT. MIND > LASTIT=. TRUE, IF<IAD.GT.MIND,AND, LASTIT? GO TO 50 SET UP FOR ASENTTO NEW "IAD".

7 *********************************************************************** END OF ITERATION LOOP ********:*************************************************************** REESTABLISH "IAD". DEPTH OFFIRST STOP IS "MIND". 50 IAD=IADTMP DFS=M IHD RETURN END ENDS