Decompression Stress in Simulated Orbital Flight

摘要

Endocrine-metabolic appraisal was made (by means of urinalysis) of human subjects experimentally exposed to hypobaric conditions similar to those encountered in orbiting spacecraft or during extravehicular activity in space. In one test, 26 subjects were exposed sequentially (after 1.5 hours of denitrogenation) to 5 p.s.i.a. for 2.5 hours, 3.5 p.s.i.a. for 15 minutes (with standardized exercise), 7 p.s.i.a. for 4 hours, and 3.5 p.s.i.a. for 2 hours (with standardized exercise). Nonspecific stress was evident, as there were decompression-induced elevations in urinary creatinine, urea, magnesium, sodium, Na/K, urine volume, 17-hydroxycortico-steroids, epinephrine (E), norepinephrine (NE), and the NE/E ratio. In a second test (n = 13), all conditions were the same as those in the first test except that there was a 4-hour exposure to 5 p.s.i.a. instead of 7 p.s.i.a. Subjects who suffered joint pain showed signs of stress before the appearance of symptoms. More intense and more progressive stress was evident in test 2, apparently reflecting the long exposure to 5 p.s.i.a. Reductions in urinary phosphorus occurred in both tests, but this is not a typical nonspecific response to stressors. (Author)