Effects of long-hose breathing.
The need for aircrew members to use long breathing hoses between regulator and mask arises in the design of new transport aircraft and in several cargo operations requiring an open rear door. In this study, induced work of breathing through long hoses, the resulting changes in oxygen consumption, and comfort were studied in relation to altitude, hose length, and  exercise level. Conclusions were that, above 18,000 ft (5.5 km), a 30-ft (9.1-m) hose is acceptable for all reasonable work levels; for altitudes between 13,000 and 18,000 ft (4.0 and 5.5 km), the hose length should preferably be 18 ft (5.5m), and at altitudes below 13,000 ft (4.0 km), hose length should be limited to 12 ft (3.6). Moreover, at ground level, the hose length should be limited to 6 ft (1.8 m) for all but sedentary activity. Should the potential for rapid decompression exist, at any altitude, volume considerations limit hose length to 18 ft (5.5 m) since larger hoses possess excessive regulator-to-mask dead space.
D000328:Adult; D000337:Aerospace Medicine; D000531:Altitude; D006801:Humans; D010101:Oxygen Consumption; D012119:Respiration; D014939:Work of Breathing