Cardiovascular function during sleep apnoeas.

common disorder which may have both mental and physical effects.l'2 It is an excellent example ofthe close interaction between respiratory and cardiac function. It is claimed that among SAS patients there is an increased risk of sudden death during sleep.3 The literature which states this is very limited, but it seems that these patients run an increase risk of developing systemic hypertension, cardiac diseases and strokes.4-6 The main pathophysiological mechanisms that are implicated in the haemodynamic changes during sleep in patients with SAS are firstly the cessation of breathing and the consequent hypoxia, and secondly the development of extreme negative intrathoracic pressures (obstructive apnoea). These two mechanisms which differentiate patients with SAS from other groups of patients who experience severe hypoxaemia during sleep but without any cessation of breathing,7 lead to a reduction in cardiac output due to