SLEEP APNOEAS

A sleep apnoea is conventionally defined as the cessation of breathing for ten seconds or more. Apnoeas, which affect around 5 per cent of adults and are markedly more common in men, may occur as frequently as 400 times per night. They can be due to a failure of the physiological drive to breathe (central sleep apnoeas) but much more often are due to a transient obstruction of the airway between the level of the soft PALATE and the LARYNX (obstructive sleep apnoeas) when the airway dilator muscles over-relax. Any factor such as alcohol or sedative drugs that accentuates this, or that makes the airway narrower (such as obesity or large TONSILS), will tend to cause sleep apnoeas.

Vigorous respiratory movements are made to overcome the obstruction during each apnoea. These are associated with snoring and snorting noises. The apnoea ends with a mini-arousal from sleep. As a result, sleep becomes fragmented and sleep deprivation, manifested as sleepiness during the day, is common. This may result in accidents – for instance, at work or while driving – and sleep apnoea is also linked with an increased risk of STROKE, heart attacks and HYPERTENSION.

The diagnosis of sleep apnoea has recently been facilitated by linking specially designed software with ELECTROCARDIOGRAPHY performed during sleep, with minimal disturbance of the subject.

Initial treatment is directed at correcting the cause (e.g. obesity), but if the apnoeas persist or are severe a nasal mask and pump which introduces air under slight pressure into the upper airway (continuous positive airway pressure, CPAP) is almost invariably effective.