VENTILATORY DYNAMICS DURING TRANSIENT AROUSAL FROM NREM SLEEP - IMPLICATIONS FOR RESPIRATORY CONTROL STABILITY

The polysomnographic and ventilatory patterns of nine normal adults we re measured during non-rapid-eye-movement (NREM) stage 2 sleep before and after repeated administrations of a tone (40-72 dB) lasting 5 s. T he ventilatory response to arousal (VRA) was determined in data sectio ns showing electrocortical arousal following the start of the tone. Me an inspiratory flow and tidal volume increased significantly above con trol levels in the first seven breaths after the start of arousal, wit h peak increases (64.2% > control) occurring on the second breath. Bre ath-to-breath occlusion pressure 100 ms after the start of inspiration showed significant increases only on the second and third postarousal breaths, whereas upper airway resistance dedined immediately and rema ined below control for greater than or equal to 7 consecutive breaths. These results suggest that the first breath and latter portion of the VRA are determined more by upper airway dynamics than by changes in t he neural drive to breathe. Computer model simulations comparing diffe rent VRA time courses show that sustained periodic apnea is more likel y to occur when the fall in the postarousal increase in ventilation is more abrupt.