Integrative control of respiration in the sleep apnea syndrome

Spontaneous pulmonary ventilation is a remarkably well-controlled process in mammals. Humans, however, may experience disturbance of ventilatory control during sleep owing to narrowing of their collapsible pharynx or alterations in the gain of the chemoreflex feedback loops. Consequently, during sleep, some fail to generate stable breathing with a level of alveolar ventilation that is appropriate for metabolic needs. Such disturbances result either from a mechanical load on the pump muscles caused by narrowing of the pharyngeal airway or from unstable chemoreflex control. The former is referred to as obstructive sleep-disordered breathing and the latter as central sleep-disordered breathing. While this dichotomous conceptualization describes severe examples of sleep-disordered breathing, current evidence suggests that both types of pathophysiologic processes co-exist, with the ultimate expression of ventilatory pattern being the outcome of a complex interplay between the obstructive and central pathophysiological processes. The article looks at this interplay to see how integrative respiration control is achieved.