226 DISSOLVED GASES IN BODY FLUIDS 



From a physiological point of view, Fig. 95 is the most significant. Both Figs. 95 and 96 

 show a continuous decrease of inert gas concentration in urine with a corresponding partial 

 pressure decrease. Referring to Fig. 96, it is obvious that the rate of inert-gas loss from the 

 body paralleled decreasing partial pressure of inert gas with time. This in itself is significant, 

 in that it is the first time such measurements have been made. The question to be asked is: 

 could the rate of inert-gas losses from the body have paralleled the decreasing chamber gas 

 pressures if the rate of decompressions were greater than 0.18 atmosphere per hour, which 

 was maintained in this experiment? In order to ascertain if a higher rate of decompression 

 could be used, one would not want to use human subjects, but instead animals should be used. 

 These studies should be performed in chamber experiments. 



In Fig. 95 the most interesting point occurred at 11 hours after the start of decompression 

 (see point A). As pointed out earlier, this was the time at which the chamber was flushed with 

 helium in order to reduce the oxygen content. Helium purging took about 30 minutes. It is in- 

 teresting to note that the time required for the dissolved nitrogen to reach its lower level (at 

 15 hours) was approximately three hours from the end of the purging time. In this time inter- 

 val the dissolved nitrogen decreased from 15 ml/liter to 5 ml/liter. This 10 ml/liter loss of 

 dissolved nitrogen is to be compared to a loss of only 2 ml/liter during a similar three-hour 

 period in Fig. 96. In the same three-hour period, the absolute partial pressure of Nj for Team 

 2 decreased by 0.45 atmospheres. For Team 3, however, the absolute partial pressure of N2 

 decreased only 0.15 atmosphere in the same time period. 



A short comment should be made concerning the base-line results reported in Table 17. 

 The values reported in this table show a close similarity in dissolved helium concentration in 

 the blood and urine. This result may be significant for Team 1, where a total of 38 urine 

 samples and 18 blood samples were taken. The statistical average deviations for these sam- 

 ples are ±10 percent. It is probably fortuitous that the results of Team 3 are similar to Team 1 

 (that is, with blood concentrations being less than the corresponding urine samples for each 

 team) . 



Helium-uptake studies were not practical, because of the lack of an adequate sample- 

 transfer system from Sealab to the support vessel topside. Samples were transferred with 

 specially designed pressure pots. These pots were heavy, bulky, and required two subjects to 

 swim out from Sealab (putting on and taking off wet suits each time), use block and tackle to lift 

 pots into Sealab, unload and load pots with samples, and then repeat the procedure to return 

 samples to the surface. Consequently the divers were reluctant to send pots up with only one 

 or two small samples. It is felt that a better and simpler transfer system, possibly a pneu- 

 matic tube, could be used for small samples. It is also felt that a study of helium uptake could 

 be performed best in a chamber experiment with the aid of a medical lock, such as the one used 

 during the decompression studies. 



One of the major faults with the present plastic syringes was the ease with which helium 

 diffused into and out of the plastic of the syringe barrel. This was first observed after a few 

 days of using the syringe. A syringe came up from Sealab for analysis but was temporarily 

 misplaced. It was analyzed 24 hours after coming topside. Previous samples had been averag- 

 ing about 45 ml/liter He, while this sample contained only 28 ml/liter. For the decompression 

 studies, this diffusion problem was minimized as the syringes were locked into the DDC until 

 needed. They were filled and immediately locked out. The sample was analyzed usually within 

 20 minutes. In future experiments all-metal syringes will be used. This defect certainly ac- 

 counted for some of the scatter in results, particularly at the greater pressures. Another 

 major factor contributing of the scatter was poor sampling technique on the part of the divers. 

 Many syringes came up with large gas bubbles in them. It is felt that much more reliable data 

 could have been obtained in this study if the subjects had been better indoctrinated and made 

 cognizant of the importance of their participation in this specific area. 



The introduction of urine samples into the valving system of the chromatograph also will 

 require modification. When the syringe quick connect was attached to the valve quick connect, 

 the pressure was immediately reduced inside the syringe. Small bubbles formed due to the 

 pressure reduction; however, the sample was immediately injected into the loop, so it is felt 

 that any gas loss was at a minimum. Some refinements should be made, particularly in view of 

 the fact that future experiments will be at greater depths and consequently at higher pressures. 

 Modifications are presently being made which will allow the introduction of the sample into the 

 loop at the pressure at which it was taken. No bubble formation can occur under these 

 conditions. 



