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CARBON DIOXIDE RETENTION DURING PROLONGED EXPOSURE TO HIGH PRESSURE ENVIRONMENT
NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
Pagination or Media Count:
In preparation for the SEALAB II project, three subjects were exposed for twelve days to seven atmosphere of pressure in an artificial environment composed of helium, oxygen, and nitrogen. Average ambient CO2 concentration was 17 surface equivalent. Resting respiratory minute volume was increased to twice normal and related to a proportional increase in tidal volume. Both oxygen consumption and CO2 excretion were elevated, resulting in a respiratory exchange ratio of 1.02. Alveolar CO2 and mixed expired CO2 were significantly higher during the exposure period. Urine CO2 excretion was markedly increased from the second day on throughout the exposure. Potassium, sodium and chloride excretion showed a transitory increase during the first four days. The pattern of urinary CO2 and electrolyte excretion reflected a response to higher CO2 load than that present in the atmosphere of the chamber during the test. All values returned to initial levels during the 27 12 hour decompression period. The observed CO2 retention is explained as the summation of increased respiratory work indicated in the 38 reduction in maximum breathing capacity, accumulated CO2 in the chamber atmosphere, and respiratory pattern of trained divers serving as subjects. In regard to the increased CO2 production, an additional factor of possible metabolic alterations is suggested. A stress response was indicated in the increased blood corticosterone levels and elevated excretion of ketosteroids. The PO2 level of 200 mm Hg did not produce any change in hemoglobin or hematocrit.
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