Ventilatory and Arousal Responses to Hypoxia and Hypercapnia in a Canine Model of Obstructive Sleep Apnea

We have previously described a canine model of obstructive sleep apnea (OSA) in which sleep–wake state is monitored continuously by a computer that produces tracheal occlusion when sleep occurs. Our aim was to assess the effects of long-term application of this model on resting ventilation and on the ventilatory and arousal responses to hypercapnia and hypoxia. Five dogs were maintained on the model for 15.5 ± 1.7 (mean ± SE) wk, with a mean apnea index of 57.5 ± 4.5 occlusions/h of sleep. Resting ventilation and the ventilatory and arousal responses to progressive hypoxic and hypercapnic rebreathing were assessed during wakefulness (W) and both slow-wave (SWS) and rapid-eye-movement (REM) sleep at baseline prior to intervention, at the end of the OSA phase, and following a 1 to 3-mo recovery period. During the period of OSA there were small changes in respiratory timing at rest, but no significant changes in Pco 2 or SaO2 . As compared with baseline, the ventilatory response to hypoxia during OSA was str...