ABSORPTION OF OXYGEN FROM THE PERITONEAL CAVITY AND THE STOMACH. By INDERJIT SINGH. From the Medical College, Rangoon University.

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1 :612.32: : ABSORPTION OF OXYGEN FROM THE PERITONEAL CAVITY AND THE STOMACH. By INDERJIT SINGH. From the Medical College, Rangoon University. (Received for publication 18th June 1933.) MANY attempts have been made in the therapeutic field to oxygenate the blood in cases of anoxaemia, by routes other than the pulmonary. Previously [Singh, 1932] an attempt was made to determine the actual rate of absorption of oxygen when the gas was injected into the subcutaneous tissue. In the present research these investigations have been extended to the peritoneal cavity and the stomach. The principle of the experiments is to estimate the oxygen consumption through the lungs of a decapitated post-absorptive cat before and after the injection of oxygen into the peritoneal cavity or the stomach. The general arrangement of the pump circuit, etc., is described in the previous paper [Singh, 1932]. The main outline of the present technique is as follows: During decapitation the animals are anaesthetised by a mixture of ether and chloroform in the proportion of 4 : 1 by volume. To the chloroform is added 1 per cent. of alcohol to prevent decomposition. Any excess of chloroform causes a decline in metabolism. After decapitation the animal is placed in 0 9 per cent. NaCl warmed to 39 C. The temperature of the bath (see fig. 1) is maintained constant by means of a cylindrical copper vessel (CB) containing water at about 600 to 800 C., this temperature being maintained by two electric immersion heaters (EH), placed in the copper vessel. The water in the copper vessel acts as a buffer between the electric heaters and the saline, preventing any sudden or wide fluctuation of temperature of the latter. The temperature of the saline is regulated by the depth to which the copper bath is immersed in the saline. The saline bath contains two stirrers (ST) worked by a motor to keep the water in gentle motion, so as to ensure uniformity of temperature of the bath. The animal can be tied by means of the supports (R) in the bath at any desired level, but with the type of artificial respiration employed the animal is not placed deeply in saline, since too great a pressure of saline prevents the expansion of the chest, and the preparation then dies from asphyxia.

2 46 Singh The tracheal cannula (TC, fig. 3) is put in communication with a closed circuit, well guarded against all leakages, by sealing every junction with paraffin wax. The circulation of air in this circuit is maintained by a pump working at the rate of 40 per minute, and having a stroke volume of 50 c.c. The soda-lime (SL, fig. 3) is placed in about 8 feet of U-shaped glass tubing, 1 inch in diameter. These tubes are guarded by a flask (F) containing saturated caustic potash solution, which condenses moisture and prevents air entering the tubes when they are not in use. The total resistance of the soda lime and the caustic potash solution a-_ WI FIG. 1. should be about 20 cm. of H20 during the inspiratory stroke of the pump. This resistance is used to force air into the lungs, and if it be too great the ventilation of the lungs is interfered with, as explained below. The soda lime tubes and the flask are placed in a water-bath at constant temperature. A thermometer (TH) is placed in the circuit to observe any change in the temperature of the air entering the spirometer. At the end of the soda-lime tube is placed a small quantity of sofnolite (SO) which changes colour if any carbon dioxide is left unabsorbed by the soda lime. To the inlet tube of the tracheal cannula is attached a water manometer (M1) which indicates the pressure at which air is pumped into the lungs; this is always adjusted so that the ventilation of the lungs remains constant. The manometer also acts as a safetyvalve in case there is undue resistance on the expiratory tube. The manometer has a side tube at its bend, to which is attached a funnel filled with water, so that if the water in the manometer is blown off it can be rapidly refilled without stopping the respiration of the animal. To the circuit is also attached a M'Lean urea-estimation burette

3 Absorption of Oxygen from Peritoneal Cavity and Stomach 47 (AIB2), by means of which a known quantity of air is withdrawn preliminary to the experiment to see if the volume recorded is functioning properly. Water manometers are included in various parts of the circuit to study the pressure changes. All exits and entrances are guardled by Y-shaped taps (see fig. 2) which can be filled and emptied by imeans of mercury. The advantage of these mercury taps is the ease with which a number of them can be opened and closed simultaneously, when one isj likely to forget to close or open a tap; also they do not leak. Tap closed FIG. 2. p open The concentration of oxygen in the inspired air is maintained at about 21 per cent. automatically. Oxygeni is entering the circuit from a volume recorder, and as the quantity entering is equal to the quantity absorbed by the lungs, the composition of the inspired air remains constant. R (fig. 3) is an adjustable resistance in the expiratory tube regulating the pressure required to expand the lungs; a constant pressure for the OVR 1 ST I KS 1G. 3. expansion of the lungs ensures constant ventilation, which in turn means a constant metabolism. A decreased ventilation leads to a decliniing metabolisin and vice versa. When the circuit is closed, the resistance of the soda lime is used to inflate the lungs, instead of R, wrhich operates while the circuit is open. ST1 and ST2 are side tubes which lead to sliding test-tubes TT1 and TT2 containiing mercury. AW'hen the test-tubes are raisecl, these openings are closed simultaneously. When the test-tubes are lowered the spirometer and the soda lime are

4 48 Singh left out of the circuit, the animal inspiring from and expiring into the room air. ITS is the inlet tube of the spirometer with a side tube to the volume recorded. OTS is the outlet tube of the spirometer. It is prolonged upwards so as to allow proper mixing of the oxygendeficient expired air and oxygen from the volume recorder. The movements of the inverted cylinder of the spirometer are limited. During each expiration it rises to a constant level, its upward progress being limited by the glass tube GL, and also by 50-gram weights (WTS) which, placed on top, give it a tendency to sink downwards. During each inspiration the cylinder sinks to a constant level and no more, its downward progress being checked by limiting the movements of the wheel (WL) fitted with a projection which strikes against a metal piece during each inspiration. The spirometer serves as a tension equalizer during the inspiratory and expiratory phases. The inlet ITS is connected to an ordinary volume recorder, of which OVR and IVR are the outlet and the inlet tubes respectively. Inside the volume recorder the outlet tube OVR bears a valve VA, which allows oxygen to pass out of the volume recorder but prevents the ingress of the air from the circuit. The valve prevents the volume recorder from being affected by the respiratory excursions of the inverted cylinder of the spirometer, and since the downward progress of the cylinder of the spirometer is limited, any diminution in volume only affects the volume recorder, the result being an evenly sloped curve. M4 is a water manometer, which measures the resistance of the valve VA; this should be negligible. CI1, a clamp, is slid up and down during the experiment; it carries the test-tubes TT1 and TT2 and the funnels MF1 and MF2, the latter being attached to CI, by means of a string over the pulley. When CI, is raised, the tubes ST1 and ST2 are closed, completing the circuit. The funnel MF1, which is filled with mercury, is also raised, thus closing the tap TP1; the funnel MF2 is lowered and the tap TP2 is opened, thus placing the volume recorder in communication with the spirometer. When CI1 is lowered the reverse happens. TP3 is a tap which places the spirometer in communication with the external air, TP4 at the same time closing and shutting off the volume recorder, when CI2 is lowered. The reverse happens when Cl2 is raised. S, an ordinary spirometer, serves as a reservoir for oxygen, the oxygen in it being kept under slight and constant pressure by placing the weight W on the top of its inverted cylinder; when CI1 is lowered the tap TP1 is opened, and the volume recorder is automatically replenished with a fresh supply of oxygen. The volume recorder is prevented from overfilling by the resistance L. T is a three-way tap connecting the volume recorder with a M'Lean burette MB1, which is used to graduate the recorder, while MB2 is the M'Lean burette attached

5 Absorption of Oxygen from Peritoneal Cavity and Stomach 49 to the main circuit. By means of the latter a known volume of air is withdrawn from the circuit to see whether the volume recorder satisfactorily records the resulting diminution in volume. Lastly, TU is a test-tube which serves as a catch for any mercury spilt over from the mercury taps and prevents it entering the spirometer and amalgamating with the lead of the joints. M3 and M2 are water manometers, indicating the pressure in various parts of the circuit. M2 always records a positive pressure, but if the valve VA does not function properly, then the manometers M3 and M4 record negative pressure. During the experiment, all that one has to do is to raise or lower the clamp CI1, because when it is raised the following happens (a) The circuit is closed. (b) The volume recorder is placed in communication with the circuit. (c) The spirometer S is disconnected with the volume recorder. On the other hand, when the clamp CI1 is lowered:- (a) The circuit is opened, the spirometer and the soda lime being disconnected from the main circuit, and the animal inspiring from and expiring into the room air. (b) The volume recorder is disconnected with the main circuit. (c) The spirometer S is connected with the volume recorder so that the latter fills up with oxygen. Thus the labour during the experiment is reduced to a minimum, the whole apparatus working almost automatically. The volume of gas in the spirometer of the circuit is about 6000 c.c., and in the recorder about 300 c.c. During the experiment oxygen enters the circuit spirometer from the volume recorder equal in amount to the oxygen absorbed by the lungs, and as the volume recorder is a small one the accuracy of measurement is quite reliable. Observations can be made by having any desired concentration of 02 in the inspired air. One point requires mention here, namely, when the motor is started the air between the pump and the resistance of the soda lime undergoes slight compression, as shown by the manometers M1 and M2, till a sufficient head of pressure is established to overcome the resistance of the soda-lime tubes, i.e. for the first few minutes more air leaves the spirometer than enters it, till equilibrium is attained, when the incoming and the outgoing volumes of air become equal. The attainment of equilibrium takes about 5 minutes, so that only after this time the pointer of the volume recorder runs parallel or colinear with the base line. All the apparatus is tested for leakage by water under pressure, especially the rubber tubing, which is very liable to deteriorate rapidly in a tropical climate such as that of Rangoon; in addition, all parts predisposed to leakage are painted with paraffin wax. VOL. XXIV., NO

6 50 Singh Before noting down the oxygen consumption, the clamp CIl is raised, thus closing the side tubes ST1 and ST2, the resistance R removed (as the resistance of the soda lime is sufficient to expand the lungs), and the pump allowed to run for ten minutes for reasons mentioned above. Then the oxygen consumption is measured for ten minutes, and then the clamp Cl1 is lowered, the resistance R restored, and the volume recorder is automatically replenished with a fresh supply of oxygen. These measurements are made at half-hourly intervals after decapitation. For example, a cat was decapitated at 9.15 a.m., the first measurement being made from 9.45 a.m. to 9.55 a.m., the second from to a.m., etc. Six experiments, in which normal metabolism was measured at half-hourly intervals over a period of more than 5 hours, gave sufficient information regarding spontaneous variations in the oxygen consumption of the preparation. Generally only three observations on normal metabolic rate were made before injection of oxygen into the peritoneal cavity or the stomach, but the number of preliminary observations in some cases had to be extended to 4, 5, or 6, since metabolism fell or rose before it became constant; sometimes it increased at first and then decreased at a constant rate. When three observations showed a constant or a constantly declining metabolism, then injection of oxygen was carried out. If the metabolism declined at a constant rate, then corrections had to be made accordingly. After injection of oxygen, 10-minute observations were continued as before at half-hourly intervals. If the metabolism had been declining constantly, then the figures obtained after injection of oxygen represented an algebraical summation of a declining metabolism and a diminishing rate of absorption. Curves were plotted, the ordinates showing consumption of oxygen per minute or in 10 minutes, the abscisse showing the time-intervals of 30 minutes each. The oxygen was warmed to 390 C. and then slowly injected into the peritoneal cavity or the stomach by displacement of water by means of two pressure bottles. The apparatus used plus the saline bath are shown in fig. 1. PB1 and PB2 are the pressure bottles, the lower one containing the oxygen and the upper one containing the water. M is a water manometer indicating any pressure in PB2. TH is a thermometer, EC an electric coil for heating the water in the bath TB, in which PB2 is immersed. WF is a weighted float, the descent of which causes a proportional rotation of a pointer P, indicating the volume of oxygen injected. P magnifies the movements of WF, and is directly under the observer's eye, thus facilitating the injection. The oxygen was injected into the peritoneal cavity a little to one side of the middle line about midway between the symphysis pubis and the subcostal angle. Any escape afterwards through the puncture was revealed as bubbles through the saline, but generally there was no

7 Absorption of Oxygen from Peritoneal Cavity and Stomach 51 escape as the needle was left in situ. This arrangement also prevented oxygen escaping from the peritoneal cavity into the subcutaneous tissue through the puncture. A post-mortem was always made to investigate and exclude such possibilities. The amount of oxygen injected was about 500 c.c. for 2000 grams weight of the animal. The oxygen injected should not cause any respiratory distress, which is indicated as increased resistance by the manometer M1 (fig. 3). In the case of the stomach no attempt was made to open the abdomen to tie the pyloric orifice; for in that case the results would have been complicated by the absorption of atmospheric oxygen by the peritoneal cavity, etc. Nor was any attempt made to open the abdomen under saline, in which case the absorption of saline by the peritoneum, hsemorrhage and shock of the operation would have acted as disturbing factors on the constancy of metabolism. So a stomach tube was passed through the cesophagus, and kept in place throughout the course of the experiment. In some cases pressure was caused by the stomach tube on the trachea, as indicated as increased resistance by the manometer M1 (fig. 3), and by asphyxial convulsions. In such cases the tube was only introduced during the time of injection and quickly withdrawn, the whole procedure occupying about a minute or two. In some cases the stomach was washed out with warm (300 C.) saline before any observations commenced. The injection of oxygen into the stomach caused a visible swelling in the epigastric region, and its persistence indicated the presence of gas in the stomach. This was confirmed by opening the abdomen at the termination of the experiment, when the gas injected was always found to be confined to the stomach, evidently being prevented from escaping into the duodenum by the pyloric sphincter. In most cases 100 c.c. of oxygen were injected. In regard to the peritoneal cavity, the observations were made in two positions, namely, supine and prone. This was done to observe any effect produced by difference in circulation in the abdomen in these two positions, since the amount of oxygen absorbed would be proportional apparently to the amount of blood circulating in unit time. Evidence was obtained from 48 human subjects in Rangoon that the pulse-rate is somewhat faster in the prone position (see Appendix I). Further, it was found that a loaded stomach impeded the circulation in the inferior vena cava of the cat in the supine position (see Appendix II). There was some evidence that oxygen was absorbed from the peritoneal cavity of the cat more rapidly in the prone position. RESULTS. The tabular matter of the details of the observations is too extensive for publication, and only the main results are given here. Six

8 52 Singh experiments covering more than 5 hours were carried out with six cats varying in weight from 1350 grams to 2750 grams, their normal oxygen consumption varying from 12 to 20K5 c.c. per minute; after the injection of oxygen into the peritoneal cavity with the animal in the supine position, the possible maximum rates of absorption of oxygen from the injected gas in the six experiments were only 0 6, 0 3, 0 6, 0 7, 0 7, and 0 4 c.c. per minute, measured at 32 C. and 760 mm. Hg. from change of oxygen consumption through the lungs. Five experiments similar to the above were performed, but with the animal in the prone position. The cats varied in weight from 1250 to 1750 grams and their normal oxygen consumption from 10 0 to 16 6 c.c. per minute. The possible maximum rates of absorption of oxygen from gas injected into the peritoneal cavity were 0 8, 0 7, 0 7, 0 7 c.c. per minute respectively. Another five experiments were conducted to determine the rate of absorption of oxygen from the stomach by the above method. The five cats varied in weight from 1040 to 2500 grams and their normal oxygen consumption from 12 3 to 21-2 c.c. per minute. The possible maximum rates of absorption of oxygen from the stomach were 0*3, 0-4, 0 3, 0 3, and 0 2 c.c. per minute respectively as measured from change in oxygen consumption through the lungs. McIver, Redfield and Benedict [1926] found that, with about 50 c.c. of oxygen injected into a cat's stomach ligatured at both cardiac and pyloric orifices, only 7 c.c. of oxygen was absorbed per hour; from this we may assume that 14 c.c. would be absorbed per hour if 100 c.c. had been injected and a larger area of the stomach exposed. This gives 0 23 c.c. per minute, which agrees fairly well with the figures for the present experiments. The possible maximum efficiency of the peritoneum, in the above eleven experiments, to saturate the blood with oxygen when compared with the lungs is in the ratio of 4.5 to 100; and the efficiency of the stomach compared with the lungs is as 2 to 100, judging from the results of the five experiments. The absorption of oxygen from the peritoneal cavity and the stomach is thus slow, and even these rates are not long maintained, the absorption falling to near nil in a few hours after the injection. This is due partly to slower diffusion as the tissues become saturated and partly to the lowering of oxygen pressure in the injected gas owing to diffusion of carbon dioxide and nitrogen from the tissues [Campbell, 1924, 1932]. SUMMARY. 1. In the decapitated cat the lungs are about twenty times more efficient in absorbing oxygen than is the peritoneal cavity filled (500 c.c.) with pure oxygen; and about fifty times more efficient than the stomach containing 100 c.c. of oxygen. In a previous research

9 Absorption of Oxygen from Peritoneal Cavity and Stomach 53 the whole subcutaneous region gave results similar to the peritoneal cavity [Singh, 1932]. 2. In human subjects living in Rangoon the pulse-rate in the prone position is always higher than in the supine position. This is perhaps a climatic effect (Appendix I). 3. The cat's stomach when filled with 100 c.c. saline apparently slows the flow of fluid through the inferior vena cava when the animal is in the supine position (Appendix II). I beg to thank Dr Argyll Campbell of the National Institute for Medical Research for help, advice and suggestions in the publication of these results. APPENDIX I. PULSE-RATE IN THE SUPINE AND PRONE POSITION IN MAN LIVING IN RANGOON. This was undertaken to determine whether the pulse-rate would reflect any circulatory variation in the abdomen in the prone position as contrasted with the supine position in man. The subject, with muscles relaxed, was made to lie supine on the floor or couch until the pulse-rate was steady; then the pulse was counted for five minutes. The subject was gently turned over and ten minutes or more were allowed to lapse before the second observation was made. In a few cases the prone position was taken before the supine. In one case the pulse was counted in a child while asleep. In certain cases the person fell asleep while the observations were made. Forty-eight subjects, 6 females and 42 males, mostly adult, were employed. In all cases the pulse was faster in the prone position on an average by about 6 beats per minute, the extreme limits for the increases being 2 and 16 beats per minute. It is suggested that one of the factors in the causation of the pulserate difference in the two positions may be the greater filling of the abdominal veins in the prone position, and hence acceleration of the pulse [Bainbridge's Law] with increased inflow into the heart in this position. MacWilliam f 1933] found no difference between pulse-rates in the supine and in the prone positions in subjects living in Britain, so that the difference recorded above may be a climatic, that is, tropical effect. APPENDIX II. EFFECT OF LOADED STOMACH ON THE CIRCULATION IN THE INFERIOR VENA CAVA. It is known that veins are much more collapsible than arteries, and are easily affected by external pressure. When an animal is in the

10 54 Absorption of Oxygen from Peritoneal Cavity and Stomach supine position, the various viscera, like the liver, the stomach, and the intestines, press upon the blood-vessels anterior to the vertebral column. The effects of pressure will be more marked if these are loaded with fluid or solid foodstuffs. An attempt was made to determine if such effects occurred, and the following procedure was adopted. The abdomen of a cat was opened above the symphysis pubis, and a wide-bore cannula inserted into the inferior vena cava. Saline was run down into the cannula from a fixed burette. The chest was then opened and the heart exposed. The heart was cut in the middle transversely and a rubber tube inserted into the right ventricle, and inclined downwards through a stab puncture on the side of the chest so that the saline flowed freely down the burette, the inferior vena cava, right auricle, and the rubber tube. A stomach tube was then passed through the cesophagus, a funnel being attached to its outer end. The cannula in the inferior vena cava was fixed with a clamp so that it could not alter its position to the slightest extent. This is important, as mere shifting of the cannula will alter the resistance to the flow of saline. The abdomen was then closed, except where the cannula emerged from it. Saline was then let in from the mark 0 to 25 of the burette. The time taken for the saline to flow between these marks was noted by means of a stop-watch, and when the observations showed a constant figure they were recorded. After ten such observations, water was poured into the funnel and the stomach filled with about 100 c.c. of water. During all this procedure the cat was untouched and unmoved so that all conditions remained constant. Three experiments were performed: in the first the times in seconds before and after filling the stomach with saline were 22 and 29; in the second experiment 20 and 2,; in the third 50 and 75. Thus there is an appreciable pressure effect. Such a phenomenon may ordinarily have little or no effect on the circulation with a healthy heart, but may be of some concern with a morbid heart, e.g. the sudden death after heavy meals. REFERENCES. CAMPBELL, J. A. (1924). J. Physiol. 59, 1. CAMPBELL, J. A. (1932). Quart. J. Exp. Physiol. 22, 159. DAVIES, H. W., and RABINOVITCH, M. (1927). J. Physiol. 64, 38P. GUTHRIE, C. C. (I 91 1). Zeits. biol. Tech. Met. 2, 138. LANGLEY, J. N. (1912). J. Physiol. 45, 239. MKIVER, M. A., REDFIELD, A. C., and BENEDICT, E. B. (1926). Amer. J. Physiol. 76, 92. MACWILLIAM, J. A. (1933). Quart. J. Exp. Physiol. 23, 10. SINGH, I. (1932). Quart. J. Exp. Physiol. 22, 193. STEWART, G. N., GUTTHRIE, C. C., BURNS, R. L., and PIKE, F. H. (1906). J. Exp. Med. 8, 289.