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

The current training program for hypoxia familiarization requires a low-pressure chamber that places aviator trainees at risk for decompression sickness. A cost-effective reduced oxygen-breathing (ROB) paradigm that decreases oxygen (O2) concentration leading to normobaric hypoxia was assessed as an alternative to the hypobaric chamber.

To help establish the validity of the ROB paradigm, this report documents cognitive performance, cardiopulmonary and subjective changes during ROB exposure.

Performance on a two-dimensional tracking task, as well as BP, heart rate, end-tidal carbon dioxide (ETCO2), O2 saturation, and subjective reports of hypoxia symptoms were observed in 12 U.S. Navy divers during exposure to normoxic air followed by one of four experimental gas mixtures per session. All participants received all gas conditions that differed in their relative concentrations of O2 and nitrogen (6.20/93.80, 7.00/93.00, 7.85/92.15, and 20.85/79.15% O2/N2).

ROB caused increases in tracking task error (p < 0.0001). ROB also increased heart rate (p < 0.001) and systolic BP (p = 0.004), and decreased ETCO2 and O2 saturation (p < 0.0001). Finally, subjects responded to ROB-induced hypoxia with higher subjective symptom ratings (p < 0.0001).

These data are consistent with those expected from hypoxic states and support the validity of the ROB paradigm for hypoxia training. Future validation studies comparing a ROB device with hypobaric chambers are needed.