Webb J T, Pilmanis A A
KRUG Life Sciences, San Antonio Division TX 78279-0644.
Aviat Space Environ Med. 1993 Sep;64(9 Pt 1):808-12.
The risk of venous gas emboli (VGE) and decompression sickness (DCS) must be determined before selection of the lowest pressure for an extravehicular activity (EVA) pressure suit which eliminates the requirement for prebreathing. In earlier studies, use of a 50% oxygen:50% nitrogen breathing mixture (50:50 mix) during 139 zero-prebreathe decompressions of male subjects to 8.3-7.8 psia resulted in 51 instances of severe VGE and one case of DCS. Our current study investigated effects of 40 zero-prebreathe decompressions of male subjects to 8.3-6.8 psia for 6 h while breathing 100% oxygen and performing moderate exercise. No DCS symptoms were observed. Severe VGE were not detected at 8.3 psia, but were present during 10%, 20%, and 40% of the exposures at 7.8, 7.3, and 6.8 psia, respectively. Zero-prebreathe decompression while breathing 100% oxygen results in significantly lower VGE and DCS risk levels than while breathing a 50:50 mix. Our results show that 7.3 psia EVA pressure suits with 100% oxygen should be safer than 8.3 psia suits with a 50:50 mix.
在选择无需预呼吸的舱外活动（EVA）压力服的最低压力之前，必须确定静脉气体栓塞（VGE）和减压病（DCS）的风险。在早期研究中，139名男性受试者在未进行预呼吸的情况下减压至8.3 - 7.8 psia，期间使用50%氧气:50%氮气的呼吸混合气（50:50混合气），出现了51例严重VGE和1例DCS。我们目前的研究调查了40名男性受试者在未进行预呼吸的情况下减压至8.3 - 6.8 psia并持续6小时，同时呼吸100%氧气并进行适度运动的影响。未观察到DCS症状。在8.3 psia时未检测到严重VGE，但在7.8、7.3和6.8 psia的暴露过程中，分别有10%、20%和40%的情况出现严重VGE。与呼吸50:50混合气相比，呼吸100%氧气时进行未预呼吸减压会使VGE和DCS风险水平显著降低。我们的结果表明，配备100%氧气的7.3 psia EVA压力服应比配备50:50混合气的8.3 psia压力服更安全。
