Central Apnea

Central apnea during sleep is a relatively common condition that can occur either as a single disorder or as part of a variety of clinical conditions. The development of central apnea represents a balance between excitatory and inhibitory influences. Central apnea occurs when arterial PCO₂ is lowered, spontaneously or experimentally, below a highly sensitive hypocapnic “apneic threshold”. The magnitude of requisite hypocapnia is referred to as the CO₂ reserve, which represents a measurable quantification of the propensity to develop central apnea. Understanding the determinants of central apnea may also enhance our understanding of the pathogenesis of obstructive sleep apnea. In fact, the development of central apnea may contribute to upper airway obstruction in susceptible individuals. In addition, variability in the propensity to develop central apnea appears to mirror the variability in the prevalence of central apnea in different populations. Furthermore, several physiologic and pharmacologic interventions may alter the CO₂ reserve. The plasticity of the apneic threshold may represent an opportunity to develop pharmacologic treatments for central apnea.