Effect of exercise on night periodic breathing and loop gain during hypoxic confinement

Hypoxic exercise exacerbates periodic breathing in otherwise healthy, awake humans. Interactions between sleep, exercise and hypoxic exposure have not been fully elucidated.

Fourteen men were confined 10 days to a simulated altitude of 4175 m (FIO2 = 0.139; PIO2 = 88 mm Hg). They were randomly assigned to an exercise intervention of 2 × 60-min cycle exercise/day at 50% of their hypoxia-specific peak power output (exercise, n = 8), or they completed no exercise (control, n = 6, random order). Sleep and breathing were objectively assessed via full polysomnography on night 1, after 14-h acute exposure (N1), and again on night 10 (N10).

The exercise group spent more time in light sleep than control on N10 (95% confidence interval (CI): 8.5-15.0%; P = 0.013) and experienced more stage shifts (CI: 13-44; P = 0.023) on both nights compared with control. The exercise group experienced more apnoea-hypopnoea (AH) events per hour compared with control (CI: 1-110; P = 0.046); AH events that were associated with night desaturations were also higher on N1 (exercise: 397 ± 320, control: 124 ± 205, P = 0.047) and N10 (exercise: 375 ± 229, control: 110 ± 138, P = 0.028, CI: 49-489 total events; P = 0.020). The length of hyperpnoea was increased from 12.8 ± 2.2 s on N1 to 14.6 ± 2.7 s on N10 (P = 0.008), and thus, total cycle length also increased (P = 0.002) in both cohorts. Mean pooled duty ratios were 0.68 ± 0.02 on N1 and 0.69 ± 0.02 on N10 (group effect P = 0.617).

Daily, moderate-intensity exercise in normobaric hypoxia equivalent to 4175 m exacerbated AH events, and negatively affected sleep architecture in exercisers compared with matched controls.