Prevalence of decompression sickness among U-2 pilots

Background: Though it is rarely reported, decompression sickness (DCS) is an expected risk for U-2 aviators. The potential for chronic sequelae of untreated DCS in this population has never been addressed. Methods: After conducting a preliminary survey at an active-duty U-2 squadron, a cohort of 416 U-2 pilots (active-duty and retired) were mailed two sequential anonymous surveys to assess demographic data, career prevalence of DCS symptoms, and overall health status with an emphasis on chronic musculoskeletal problems. Results The response rate for each mail-in survey was over 60%. During their career, 75.5% of pilots experienced DCS symptoms such as joint pain, skin manifestations, and/or various neurological problems. Symptoms generally started during flight and resolved upon descent. Many pilots voluntarily increased their oxygen prebreathing time, or inflated the pressure suit during flight to prevent or treat symptoms. At some point in their career 12.7% of those experiencing symptoms either altered the flight profile or aborted a mission as a result The association of past DCS with current arthritic problems was not statistically significant. Conclusions The career prevalence of DCS symptoms in U-2 pilots is higher than previously reported, and these symptoms sometimes affect mission completion. We found no evidence that chronic musculoskeletal sequelae (e.g., arthritis or dysbaric osteonecrosis) are causally associated with DCS in this population.