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Publication AbstractsThe Effect of Simulated Weightlessness on Hypobaric Decompression SicknessUlf I. Balldin, Andrew A. Pilmanis, and James T. WebbAviat Space Environ Med 2002; 73:773-8 AbstractBackground: A discrepancy exists between the incidence of ground-based decompression sickness (DCS) during simulated extravehicular activity (EVA) at hypobaric space suit pressure (20-40%) and crewmember reports during actual EVA (zero reports). This could be due to the effect of gravity during ground-based DCS studies. Hypothesis: At EVA suit pressures of 29.6 kPa (4.3 psia), there is no difference in the incidence of hypobaric DCS between a control group and group exposed to simulated weightlessness (supine body position). Methods: Male subjects were exposed to a hypobaric pressure of 29.6 kPa (4.3 psi) for up to 4 h. The control group (n = 26) pre-oxygenated for 60 min (first 10 min exercising) before hypobaric exposure and walking around in the altitude chamber. The test group (n = 39) remained supine for a 3 h prior to and during the 60-min pre-oxygenation (also including exercise) and at hypobaric pressure. DCS symptoms and venous gas emboli (VGE) at hypobaric pressure were registered. Results: DCS occurred in 42% in the control and in 44% in simulated weightlessness group (n.s.). The mean time for DCS to develop was 112 min (SD ± 61) and 123 min (± 67), respectively. VGE occurred in 81% of the control group subjects and in 51% of the simulated weightlessness subjects (p = 0.02), while severe VGE occurred in 58% and 33%, respectively (p = 0.08). VGE started after 113 min (± 43) in the control and after 76 min (± 64) in the simulated weightlessness group. Conclusions: No difference in incidence of DCS was shown between control and simulated weightlessness conditions. VGE occurred more frequently during the control condition with bubble-releasing arm and leg movements.Keywords: decompression sickness, simulated weightlessness, hypobaric exposure, venous gas emboli, space environment. Information on subscribing, and on obtaining copies of an article or of an entire issue. Table of Contents for Volume 73, Number 8 of the ASME journal.
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