Schwarz EI, et al. - Whether obstructive sleep apnoea (OSA) patients experience nocturnal cerebral hypoxia that is prevented by continuous positive airway pressure (CPAP), was investigated. A 2-week intervention was carried out wherein OSA patients were randomly allocated to either subtherapeutic or therapeutic CPAP. Changes in oxygenation at end of the 2-week intervention were compared between groups. OSA recurrence occurred in all 9 using subtherapeutic and in 0 using therapeutic CPAP among 21 patients (mean apnoea/hypopnoea-index 50.3/h). Findings suggested a role of cerebral hypoxia in predisposing untreated OSA patients to cerebral damage as nocturnal cerebral deoxygenation attributed to CPAP-withdrawal was evident in OSA patients.