The reduced oxygen breathing paradigm for hypoxia training: Physiological,cognitive, and subjective effects

The current training program for hypoxia familiarization requires a low-pre ssure chamber that places aviator trainees at risk for decompression sickne ss. A cost-effective reduced oxygen-breathing (ROB) paradigm that decreases oxygen (O-2) concentration leading to normobaric hypoxia was assessed as a n alternative to the hypobaric chamber. Purpose: Tn help establish the vali dity of the ROB paradigm, this report documents cognitive performance, card iopulmonary and subjective changes during ROB exposure. Methods: Performanc e on a two-dimensional tracking task, as well as BP, heart rate, end-tidal carbon dioxide (ETCO2), O-2 saturation, and subjective reports of hypoxia s ymptoms were observed in 12 U.S. Navy divers during exposure to normoxic ai r followed by one of four experimental gas mixtures per session. Ali partic ipants received all gas conditions that differed in their relative concentr ations of O-2 and nitrogen (6.20/93.80, 7.00/93.00, 7.85/92.15, and 20.85/7 9.15% O-2/N-2). Results: ROB caused increases in tracking task error (p < 0 .0001). ROB also increased heart rate (p < 0.001) and systolic BP (p = 0.00 4), and decreased ETCO2 and O-2 saturation (p < 0.0001). Finally, subjects responded to ROB-induced hypoxia with higher subjective symptom ratings (p < 0.0001). Conclusions: These data are consistent with those expected from hypoxic states and support the validity of the ROB paradigm for hypoxia tra ining. Future validation studies comparing a ROB device with hypobaric cham bers are needed.