Fig. 2.

A recording of breath-by-breath minute ventilation values recorded from a human participant before, during and following exposure to 12 episodes of hypoxia Each hypoxic episode and subsequent recovery period was 4 min in duration with the exception of the last recovery period, which was 30 min in duration. Note that during exposure to intermittent hypoxia the ventilatory response to hypoxia gradually increased from the initial hypoxic episode to the final hypoxic episode. This phenomenon is referred to as progressive augmentation. Also note that during exposure to intermittent hypoxia minute ventilation gradually increased during the normoxic recovery periods so that it was substantially higher during the final recovery period compared with baseline. This phenomenon is referred to as ventilatory long-term facilitation. Reprinted with permission from “Intermittent hypoxia and respiratory plasticity in humans and other animals: does exposure to intermittent hypoxia promote or mitigate sleep apnoea,” by J.H. Mateika and G. Narwani. Exp. Physiol. 94: 279–296, 2009.