The pharyngeal airway narrows when pharyngeal muscle tone decreases. During sleep, partial collapse at this level leads to snoring, and complete collapse to obstructive sleep apnoea , Such upper airway incompetence is relatively common: 17% of randomly selected normal British men snore ; one in 300 have severe obstructive sleep apnoea and cannot maintain a patent airway in any sleeping posture . In hospital inpatient cohorts the prevalence is greater still. In one middle-aged group with ischaemic heart disease, significant obstructive sleep apnoea affected 14% of the sample . Obstructive sleep apnoea has a range of undesirable acute effects which may be avoided by appropriate management. This review considers the causes of upper airway collapse, its consequences and treatment for the patient in hospital.