Introduction

Obstructive sleep apnoea is usually referred to as Obstructive Sleep Apnoea/Hypopnoea Syndrome (OSAHS) as it provides a more accurate description of the condition. OSAHS is caused by blockage of the airway, typically when the soft tissue at the back of the throat collapses during sleep due to lack of muscle tone, predominantly during rapid eye movement (REM) sleep. OSAHS is common and is one extreme of a continuum of sleep-disordered breathing (SDB) (Young et al., 1993) that ranges from normality with few obstructive events, to a life-threatening condition, which may present with cardiovascular, respiratory, or sleep related symptoms (Shneerson, 2000). OSAHS differs from central sleep apnoea, which is caused by problems with brain mechanisms that control breathing and can be found in patients with cardiac failure or neurological disease, particularly stroke (Douglas, 2002) (see ‘Stroke’).

The currently accepted definition of OSAHS is the co-existence of at least five obstructive breathing events per hour of sleep with unexplained excessive daytime sleepiness or at least two other major symptoms (American Sleep Disorders Association, 1999). Apnoeas are characterized by repeated nocturnal episodes of cessation of airflow and hypopnoeas as a 50% reduction in airflow, with both lasting for at least ten seconds (Schneerson, 2000). These obstructed breathing events are terminated by arousals from sleep and are sometimes associated with temporary dips in oxygen saturation (Engleman & Joffe, 1999).