Occurrence of Cortical Arousal at Recovery from Respiratory Disturbances during Deep Propofol Sedation

Recent evidences suggest that non-arousal mechanisms can restore and stabilize breathing in sleeping patients with obstructive sleep apnea. This possibility can be examined under deep sedation which increases the cortical arousal threshold. We examined incidences of cortical arousal at termination of apneas and hypopneas in elderly patients receiving propofol sedation which increases the cortical arousal threshold. Ten elderly patients undergoing advanced endoscopic procedures under propofol-sedation were recruited. Standard polysomnographic measurements were performed to assess nature of breathing, consciousness, and occurrence of arousal at recovery from apneas and hypopneas. A total of 245 periodic apneas and hypopneas were identified during propofol-induced sleep state. Cortical arousal only occurred in 55 apneas and hypopneas (22.5%), and apneas and hypopneas without arousal and desaturation were most commonly observed (65.7%) regardless of the types of disordered breathing. Chi-square test indicated that incidence of no cortical arousal was significantly associated with occurrence of no desaturation. Higher dose of propofol was associated with a higher apnea hypopnea index (r = 0.673, p = 0.033). In conclusion, even under deep propofol sedation, apneas and hypopneas can be terminated without cortical arousal. However, extensive suppression of the arousal threshold can lead to critical hypoxemia suggesting careful respiratory monitoring.