Webb J T, Pilmanis A A, O'Connor R B
KRUG Life Sciences Inc., San Antonio, TX 78214, USA.
Aviat Space Environ Med. 1998 Apr;69(4):335-40.
The altitude threshold for decompression sickness (DCS) symptoms has been variously described as being 18,000 ft (5,487 m) to above 25,000 ft (7,620 m). Safety and efficiency of aerospace operations require more precise determination of the DCS threshold.
Subjects were 124 males who were exposed to simulated altitudes (11 at 11,500 ft; 10 at 15,000 ft; 8 at 16,500 ft; 10 at 18,100 ft; 10 at 19,800 ft; 20 at 21,200 ft; 20 at 22,500 ft; 10 at 23,800 ft, and 25 at 25,000 ft) for 4 to 8 h. All breathed 100% oxygen beginning with ascent. Subjects were monitored for precordial venous gas emboli (VGE) and DCS symptoms. Probit curves representing altitude vs. incidence of DCS symptoms and VGE allowed estimation of respective risk.
VGE were first observed at 15,000 ft with increasing incidence at higher altitudes; over 50% at 21,200 ft and 70% or higher at 22,500 ft and above. The lowest altitude occurrence of DCS was a 5% incidence at 21,200 ft. At 22,500 ft, the DCS incidence abruptly climbed to 55%.
A 5% threshold for DCS symptoms was concluded to be 20,500 ft under the conditions of this study. The abrupt increase in DCS symptoms, with zero-preoxygenation exposure above 21,200 ft implies a need for reconsideration of current USAF and FAA altitude exposure guidance.
减压病（DCS）症状的海拔阈值有多种描述，范围从18,000英尺（5,487米）到25,000英尺（7,620米）以上。航空航天作业的安全性和效率需要更精确地确定DCS阈值。
受试者为124名男性，他们暴露于模拟海拔高度（11,500英尺有11人；15,000英尺有10人；16,500英尺有8人；18,100英尺有10人；19,800英尺有10人；21,200英尺有20人；22,500英尺有20人；23,800英尺有10人，25,000英尺有25人）4至8小时。所有人从上升开始就呼吸100%的氧气。对受试者进行心前区静脉气体栓塞（VGE）和DCS症状监测。代表海拔与DCS症状和VGE发生率的概率曲线可用于估计各自的风险。
VGE首次在15,000英尺处被观察到，在更高海拔处发生率增加；在21,200英尺处超过50%，在22,500英尺及以上处达到70%或更高。DCS的最低海拔发生率在21,200英尺处为5%。在22,500英尺处，DCS发生率突然攀升至55%。
在本研究条件下得出，DCS症状的5%阈值为20,500英尺。在21,200英尺以上零预充氧暴露情况下DCS症状的突然增加意味着需要重新考虑美国空军和联邦航空管理局当前的海拔暴露指南。
