Ventilatory long-term facilitation in non-snoring subjects during NREM sleep.

We hypothesized that very brief episodes of hypoxia (<1 min) would evoke long-term facilitation (LTF) in individuals free of inspiratory flow limitation (IFL). We studied 12 healthy participants who were self-reported non-snorers and confirmed the absence of IFL. We induced 15 brief episodes of hypoxia during non-REM sleep, reducing arterial oxygen saturation to 84-85%, followed by 1 min of room air. Ventilatory variables and resistance were measured during the control period, hypoxic trials, room air controls, and for 20 min following the last hypoxic episode. There was a significant increase in minute ventilation (108+/-1.3% of control, P < 0.05) and tidal volume (105+/-1.7% of control, P < 0.05) and a significant decrease in upper airway resistance (88+/-9.8% control, P < 0.05) during the recovery period. However, there were no significant changes in any variable during sham studies. We have shown for the first time that LTF can be elicited in sleeping humans free of IFL.