Abstract
Nocturnal periodic breathing manifests as a crescendo-decrescendo breathing pattern with alternating central events and is a common finding during sleep in patients with chronic heart or during stays at high altitude. Despite its regular occurrence during sleep studies, well-defined diagnostic criteria and specific treatment options, the pathophysiology of periodic breathing is not completely understood. An increasing likelihood for the occurrence of periodic breathing is observed for different conditions which may be comorbid to chronic heart failure including atrial fibrillation or pulmonary hypertension. In addition, studies oftentimes report an association with an increased sympathetic tone, cortical arousals, fluid shifts and oxygen desaturations. In patients with chronic heart failure, hypoxemia seems to be the most consistent finding, but tends to be overlooked on blood gas analysis due to compensatory breathing (“hypoxemic drive”) which causes an excess exspiration of CO2 of the main controlled variable by enhanced respiration. This increase in respiratory effort also occurs in metabolic acidosis due to renal failure and may be the cause of ventilatory instability and nocturnal periodic breathing. Based on the current knowledge about periodic and clinical observations in patients with chronic heart failure and chronic kidney disease, a pathophysiological concept on nocturnal periodic breathing is outlined. The essential feature of this theory includes recurrent episodes of hypoxemia and acidemia detected by peripheral chemoreceptors causing a temporarily increased respiratory drive which destabilizes respiration due to a time delay between peripheral sensation of pO2 and central chemoreception of pCO2.