title: Pathogenesis of central and complex sleep apnoea.
abstract: Central sleep apnoea (CSA) - the temporary absence or diminution of ventilatory effort during sleep - is seen in a variety of forms including periodic breathing in infancy and healthy adults at altitude and Cheyne-Stokes respiration in heart failure. In most circumstances, the cyclic absence of effort is paradoxically a consequence of hypersensitive ventilatory chemoreflex responses to oppose changes in airflow, that is elevated loop gain, leading to overshoot/undershoot ventilatory oscillations. Considerable evidence illustrates overlap between CSA and obstructive sleep apnoea (OSA), including elevated loop gain in patients with OSA and the presence of pharyngeal narrowing during central apnoeas. Indeed, treatment of OSA, whether via continuous positive airway pressure (CPAP), tracheostomy or oral appliances, can reveal CSA, an occurrence referred to as complex sleep apnoea. Factors influencing loop gain include increased chemosensitivity (increased controller gain), reduced damping of blood gas levels (increased plant gain) and increased lung to chemoreceptor circulatory delay. Sleep-wake transitions and pharyngeal dilator muscle responses effectively raise the controller gain and therefore also contribute to total loop gain and overall instability. In some circumstances, for example apnoea of infancy and central congenital hypoventilation syndrome, central apnoeas are the consequence of ventilatory depression and defective ventilatory responses, that is low loop gain. The efficacy of available treatments for CSA can be explained in terms of their effects on loop gain, for example CPAP improves lung volume (plant gain), stimulants reduce the alveolar-inspired PCO2difference and supplemental oxygen lowers chemosensitivity. Understanding the magnitude of loop gain and the mechanisms contributing to instability may facilitate personalized interventions for CSA.
authors: Division of Pulmonary and Critical Care Medicine, University of California San Diego, La Jolla, California, USA.
authors: Jeremy E
authors: JE
authors: Orr
authors: Division of Pulmonary and Critical Care Medicine, University of California San Diego, La Jolla, California, USA.
authors: Atul
authors: A
authors: Malhotra
authors: Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.|Department of Allergy Immunology and Respiratory Medicine and Central Clinical School, The Alfred and Monash University, Melbourne, Victoria, Australia.
authors: Scott A
authors: SA
authors: Sands
mesh_terms: D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006801:Humans; D020182:Sleep Apnea, Central / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D020181:Sleep Apnea, Obstructive / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D016896:Treatment Outcome
keywords: central apnoea; loop gain; periodic breathing; ventilatory instability