Aviator 'Bends' Pain as Influenced by Altitude and In-Flight Denitrogenation

Abstract : After aviator's bend pains were pre-established by exposure to a simulated altitude of 38,000 ft, the average critical altitude (CA) determined for severe pain was 31,600 ft, the CA for moderate pain was 28,500 ft, and the CA disappearance or reappearance of mild pain was 23,900 ft. Subjects with bends, when kept without exercise (stored) at 10,000 to 15,000 ft, showed a reduction in bends with time; a 12,000 or 13,000 ft increase over the former CA'a occurred in 3 hrs. No increase in CA occurred after storing at 20,000 or 25,000 ft for 3 hrs, presumably because of the growth of subclinical tissue bubbles. The results indicate that inflight denitrogenation should be conducted at 10,000 to 15,000 ft. Oxygen economy was aided without sacrificing protection by breathing cabin air at 10,000 ft during the first hr of a longer period of breathing full oxygen at 15,000 ft. A discussion is appended concerning the symptoms other than bends which result from altitude-chamber decompression.