BREATHING DURING SLEEP: THE RESPONSES TO ASPHYXIA and PROCHLORPERAZINE IN NORMAL SUBJECTS and PATIENTS WITH OBSTRUCTIVE SLEEP APNEA*

:The effects of sleep and prochlorperazine (12.5 mg intravenous bolus) on the ventilatory and arousal responses to asphyxia were studied in normal subjects and patients with obstructive sleep apnea (OSA). The ventilatory response to asphyxia was reduced during non-rapid eye movement sleep in the six normal subjects studied (1.93 ± 0.181 min^-1. % SaO₂ awake vs. 1.01 ± 0.10 I min^-1. ± SaO₂ asleep; rnean ± SEM; p<0.01) (SaO₂= arterial oxygen saturation). In the two normal subjects studied during sleep following prochlorperazine administration, ventilatory responsiveness was increased (p<0.05) but arousal response to asphyxia was depressed (p<0.025). Although prochlorperazine increased waking ventilatory responsiveness to asphyxia in five of six patients with OSA (2.26 ± 0.44 I min^-1.% SaO₂vs.4.77 ± 1.39 I min^-1.% SaO₂; mean ± SEM; p<0.01), the drug had no clinically significant effect on upper airway obstruction during sleep; in three patients, apnea frequency was slightly reduced but in four of six patients severity of hypoxemia during apnea was increased with drug administration. We conclude that prochlorperazine administration is unlikely to benefit patients with obstructive sleep apnea despite its ventilatory effects during wakefulness and sleep. This lack of effect may be explained by separate effects of the drug on ventilatory and arousal responses to asphyxia. (Aust NZ J Med 1983; 13: 613–620.)