Increases in arterial oxygen saturation (SaO(2)) in response to intermittent hypoxic exposure (IHE) are well established. However, IHE protocols have historically involved static hypoxic environments. The effect of a dynamic hypoxic environment on SaO(2) is not known.

The purpose of this study was to examine the effect of dynamic IHE conditioning on SaO(2) using the Cyclical Variable Altitude Conditioning Unit.

Methods.-Thirteen trained participants (9 males, age 30.1 +/- 9.2 years; 4 females, age 30.3 +/- 8.9 years) residing at or near sea level were exposed to a 7-week IHE conditioning protocol (mean total exposure time = 30.8 hours). Participants were exposed to a constantly varying series of hypobaric pressures simulating altitudes from sea level to 6858 m (22 500 feet) in progressive conditioning tiers, creating a dynamic hypoxic environment. SaO(2) was evaluated using pulse oximetry (SpO(2)) 4 times: at 2740, 3360, and 4570 m, prior to and following the first 3 weeks of IHE, and at 4570. 5490, and 6400 in at the start and end of the final 4 weeks.

Results.-SpO(2) improved 3.5%, 3.8%, and 4.1% at 2470, 3360, and 4570 m, respectively (P < .05), and 3.3%, 3.4%, and 5.9% at 4570, 5490, and 6400 m, respectively (P < 05). At 4570 in, SpO(2) increased from 81.7% +/- 6.5% to 89.1% +/- 3.2% over the entire 7-week conditioning period.

The dynamic intermittent hypoxic conditioning protocol used in the present study resulted in an acclimation response, such that SPO2 was significantly increased at all altitudes tested, with shorter exposure times than generally reported.

Hetzler, R.K., Stickley, C.D., Kimura, I.F., Labotz, M. et al., (2009). Wilderness and Environmental Medicine. 20, 1, 26-32.

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