Behavioural hyperventilation as a novel clinical condition associated with central sleep apnoea: a report of three cases.

Central sleep apnoea (CSA) is a disorder characterised by repetitive episodes of decreased ventilation due to complete or partial reduction in the central neural outflow to the respiratory muscles. Hyperventilation plays a prime role in the pathogenesis of CSA. Chronic heart failure and dwelling at high altitude are classical conditions in which CSA is induced by hyperventilation. Hyperventilation syndrome (HVS) is a prevalent behavioural condition in which minute ventilation exceeds metabolic demands, resulting in haemodynamic and chemical changes that produce characteristic dysphoric symptoms. HVS is frequently caused by anxiety disorders and panic attacks. Until now, medical literature has focussed primarily on daytime symptoms of behavioural hyperventilation. It is currently unknown how this condition may affect sleep. Three cases are reported in which behavioural hyperventilation was associated with occurrence of significant central sleep apnoea, which was not present during normal tidal breathing in steady sleep. Therefore, behavioural hyperventilation should be added to the list of known clinical conditions associated with CSA.