Central Sleep Apnoea

Central Sleep Apnoea/Cheyne Stokes Breathing

Cycles of under breathing (hyponoeas) shown in blue and breathing stoppages (apnoeas), shown in red in a man with severe heart failure on maximal drug treatment using a relatively simple home sleep:breathing study (ApneaLink Plus). The top panel shows the whole night with blue lines showing periods of low blood oxygen (hypoxia)

This type of breathing disorder occurs during sleep in those with heart failure. Known to occur since the early 1900s it results in alternating cycles of over breathing, or hyperventilation, followed by breathing stoppages without an attempt to breathe during them called central (sleep) apnoeas. The traditional medical term has been paroxysmal nocturnal dyspnoea or PND. Although OSA can cause heart failure, this condition is due to heart failure, not the other way around. As the sufferer is not attempting to breathe during the apnoea, it is relatively silent and those who had snoring or OSA before heart failure developed, are noticed to have gone quiet but this is not as good as it might seem. The condition is conventionally diagnosed by a full diagnostic sleep study (PSG) but is a very variable condition which changes between sleep stages, with sleeping posture, disease progression and in response to heart failure treatment. 

Central sleep apnoea/Cheyne-Stokes respiration forms part of a downward spiral in heart failure and although CSA is common in heart failure at worst only 70% of heart failure sufferers will develop it. This condition will change as heart failure status changes; it may improve in response to drug or device-based treatments for heart failure.

The physiology of CSA in heart failure is complex but leads to unstable breathing patterns in which there are alternating cycles of over-breathing (hyperventilation) and under-breathing (hypoventilation or apnoeas). Hyperventilation lowers CO2 in the blood (hypocapnia) which acts on the breathing control centres in the brainstem and reduces or actually stops breathing efforts. When breathing resumes it is excessive and hyperventilation recurs.

Treating this type of sleep apnoea starts with optimising the conventional treatment of heart failure but positive airway pressure either simple (CPAP, BiPAP®, or VPAP™) or more complex treatment (Adaptive Servoventilation or ASV) can improve both the sleep apnoea and heart failure. Major clinical trials are underway to answer these and other questions.