DISSOLVED GASES IN BODY FLUIDS 221 



With helium at the inert carrier, it is possible to analyze carbon dioxide, oxygen, and 

 nitrogen. 



During the early phases of Sealab II, it was planned to conduct chromatographic analysis 

 of urine in an effort to obtain preliminary data on gas uptake. Due to logistic difficulties, this 

 procedure was not considered feasible. 



During the decompression cycle, it was possible to conduct a program of urine monitoring 

 each hour. 



The graphic presentation of each hourly analysis, presented in the following pages, indica- 

 tes that a high correlation exists between the amount of dissolved gas in the urine and the am- 

 bient atmospheric concentration. Application of this observation to decompression schedules 

 is under serious consideration. 



The detailed report of this work follows. 



DETERMINATION OF DISSOLVED GASES IN BODY FLUIDS 



The objective of the work performed by the Ocean Sciences and Engineering Division, NHL, 

 was the measurement of dissolved gases in body fluids. In particular, measurements were to 

 be made of the rate at which the concentration of dissolved gases in body fluids responds to 

 changing pressure conditions experienced by the Sealab divers. Studies were to be made of the 

 rate of helium uptake immediately after descent into the atmospheric enviroment of Sealab and 

 of the rate of elimination of helium and nitrogen during the decompression stage. The latter 

 study is of particular importance, because the rate of gas elimination determined the optimum 

 safe rate of decompression. 



An analytical technique utilizing gas chromatography, developed at NRL for the determina- 

 tion of dissolved gases in liquids, was used to determine helium and nitrogen in blood and urine 

 of the Sealab divers. Two Fisher Model 25 gas partitioners were used in this work. One em- 

 ployed an argon carrier gas with an activated charcoal column and was used for helium deter- 

 minations. The other chromatograph used helium carrier gas with a molecular sieve column 

 and was used for N2 determination. The method has been described in detail in various publi- 

 cations [1, 2, 3]. 



Special plastic syringes were developed for obtaining urine samples under high pressure. 

 Fig. 94 is a picture of one of the syringes used in Sealab. The main body of the syringe is 2 in. 

 O. D. and 1 in. I. D. The length of the plastic housing is 5 in. One end is fitted with a Swagelok 

 quick connector. The plunger is made of brass or aluminum and has O-ring seals. Four 

 screws pass through the back flange of the syringe; these screws with nuts are used to prevent 

 the plunger from backing out when the external pressure is reduced. When filling the syringe 

 with urine, the plunger is removed and the barrel is carefully filled. The plunger is then fitted 

 into the barrel. All bubbles are expelled through the quick connector, and the plunger is 

 pushed in until the four screws protrude through the back flange. The nuts are then tightented 

 with a small wrench. The above procedures all take place in Sealab, or the deck decompres- 

 sion chamber (DDC). The syringe was then sent topside for analysis. The syringe quick con- 

 nector was then fastened to its couterpart quick connector, which was attached to the sampling- 

 valve inlet of the stripping chamber. The urine was then forced into the sampling loop of the 

 valve and immediately injected into the stripping chamber. While this method works very well 

 for sea water or any liquid at one atmosphere, some shortcomings were evident when injecting 

 samples under pressure. This problem will be discussed later. 



A modified Hamilton glass syringe was used for blood analysis. A Hamilton luer lock two- 

 way valve was used on the front end of the syringe. The plunger has a Chaney adaptor modi- 

 fied with an aluminum stop to retain the plunger in position under pressure when the syringe 

 was sent topside. The plunger was also fitted with an O-ring to insure a leak-tight fit. The 

 blood was heparinized to prevent clotting. Blood samples were injected through a serum cap 

 directly into the stripping chamber. A sampling program for obtaining blood and urine from 

 the Sealab subjects was arranged by Captain Walter Mazzone, MSC, USN (Physiological Mea- 

 surement Officer), for both the helium uptake and elimination studies. 



