Webb JT, Krock LP, Gernhardt ML. Oxygen consumption at altitude as a risk factor for altitude decompression sickness. Aviat Space Environ Med 2010; 81:987–92. Introduction: The existence of a general influence of exercise on the incidence of decompression sickness (DCS) has been known for more than a half-century. However, quantification of the effect has not been done for several reasons, including isolation of exercise as the only variable. The DCS database at Brooks City-Base, TX, contains detailed physiologic information on over 3000 altitude exposures. The purpose of this study was to measure <inline-graphic xlink:href="987inf1.gif"/>o₂ during the activities performed during those exposures to retrospectively determine if <inline-graphic xlink:href="987inf1.gif"/>o₂, a quantifiable index of exercise intensity, was related to the level of reported DCS. Methods: Ground-level activity was designed to duplicate the standardized activity during the altitude exposures. Breath-by-breath <inline-graphic xlink:href="987inf1.gif"/>o₂ was determined for each activity using a COSMED® metabolic measurement system. Comparison of the <inline-graphic xlink:href="987inf1.gif"/>o₂ during four levels of activity performed under otherwise comparable conditions allowed a determination of correlation between <inline-graphic xlink:href="987inf1.gif"/>o₂ and DCS risk observed during the altitude exposures. Results and Discussion: Four previous altitude exposure profiles at 8992 m to 9144 m (29,500 to 30,000 ft; 231 to 226 mmHg) for 4 h following a 1-h prebreathe resulted in 38–86% DCS. This study provided the o2<sub/> of activities during those studies. The correlation between DCS incidence and the highest 1-min <inline-graphic xlink:href="987inf1.gif"/>o₂ of activity was 0.89. Conclusion: The highest 1-min <inline-graphic xlink:href="987inf1.gif"/>o₂ showed a high correlation with level of DCS risk. Future exposures involving lower levels of activity could provide data that would allow improvement in modeling of DCS risk.