Clinical diagnosis and assessment of obstructive sleep apnoea syndrome

Obstructive sleep apnoea (OSA) syndrome is very common, affecting up to 4% of adult males. The pathophysiology of OSA is complex and incompletely understood, but upper airway (UA) obstruction appears to be the net result of an inability of the UA dilating muscles to maintain a patent oropharyngeal airway during sleep. A narrowed UA is common among OSA patients, and in adults this is usually due to nonspecific factors, such as fat deposition in the neck, or abnormal bony morphology of the UA. The present criteria for the diagnosis of OSA are not well-defined, and different centres use different thresholds of apnoea and hypopnoea frequency during sleep to diagnose the clinical syndrome. The advent of many simplified diagnostic systems, some of which are portable and suitable for use in the patient's home, represents a major advance, but many of these systems are poorly validated, and there is no uniformity of measured variables among the various systems, apart from arterial oxygen saturation (Sa,O2). The established prevalence of OSA among the general population implies that most patients with suspected OSA should be initially assessed outside major sleep laboratories, in many cases by clinicians who may not have as detailed an understanding of the syndrome as clinicians who have undertaken specific training in sleep medicine. It is important, therefore, that clear-cut guidelines and criteria be established for the assessment and management of patients with suspected OSA.