Central Sleep Apnoea
The term central sleep apnoea encompasses a group of sleep-related breathing disorders in which respiratory effort is diminished or absent in an intermittent or cyclical fashion during sleep. In most cases, central sleep apnoea is associated with obstructive sleep apnoea syndromes or is caused by an underlying medical condition, recent ascent to high altitude, or narcotic use. Primary central sleep apnoea is a rare condition, the etiology of which is not entirely understood.
During polysomnography (PSG), a central apnoeic event is conventionally defined as cessation of airflow for 10 seconds or longer without an identifiable respiratory effort. In contrast, an obstructive apnoeic event has a discernible ventilatory effort during the period of airflow cessation.
In general, treatment of central sleep apnoea is often more difficult than treatment of obstructive sleep apnoea and treatment varies according to the specific syndrome. Central sleep apnoea in adults includes primary central sleep apnoea, Cheyne-Stokes breathing-central sleep apnoea (CSBCSA) pattern, high-altitude periodic breathing, central sleep apnoea due to medical conditions other than Cheyne-Stokes, and central sleep apnoea due to drugs or substances.
During sleep, behavioural control is lost and chemical control is the major mechanism regulating ventilation. Central sleep apnoea is most often seen during non–rapid eye movement (NREM) sleep, when behavioural influence is least, followed by rapid eye movement (REM) sleep, while a fully awake person is least likely to manifest it. Despite these changes, ventilatory control during sleep remains similar to that during wakefulness.
The types of pathophysiologic phenomena which can cause central sleep apnoea syndromes are ventilatory instability or depression of the brainstem respiratory centres or chemoreceptors.