[Heart failure and central respiratory dysregulation. Cheyne-Stokes respiration during sleep in advanced left heart...

Central sleep apnoea, especially Cheyne-Stokes respiration, is found in 45 to 66% of patients with congestive heart failure (CHF) in functional classes NYHA II to IV. Cheyne-Stokes breathing cycles are characterised by central apnoeas, followed by a crescendo--like increase of tidal volume into hyperventilation and a subsequent decline of tidal volume, ending in another central apnoea. Cheyne-Stokes respiration has been shown to be a poor prognostic factor for patients with CHF. Apnoeas and hypopnoeas cause marked oxygen desaturation and rises of carbon dioxide concentrations in the blood. The resumption of breathing is frequently associated with arousals, which might cause daytime symptoms like fatigue and sleepiness as well as persistent activation of the sympathetic nervous system. Elevated concentrations of catecholamines increase cardiac work, adversely affecting cardiac function. Serum catecholamines are known to augment the chemoreceptor susceptibility for carbon dioxide. This might be one reason for the permanent mild hyperventilation found in these patients during wakefulness. Increased chemoreceptor responsiveness destabilises the feedback control of breathing, and hyperventilation below the apnoeic threshold grows more likely. Other contributing factors for the development of Cheyne-Stokes respiration include alterations in the control of breathing during sleep and the increased circulation time between the lung and chemoreceptors in CHF patients. The feedback regulation of breathing might be less dampened since carbon dioxide levels are reduced in these patients. Treatment includes nCPAP, but in many cases this is poorly tolerated in patients with central sleep apnoea. Future approaches to Cheyne-Stokes respiration might focus on improving ventilatory pattern and pharmacological manipulation of carbon dioxide receptor susceptibility.