Role of Sleep and Fatigue in Genesis of Respiratory Insufficiency

Abstract

Changes in respiration during sleep in normal man include a decrease in minute ventilation, inspiratory flow rate [1], respiratory responsiveness to hypoxia or hypercapnia [2], and respiratory muscle tone. Short periods of apnoea (less than 10 seconds) occurring less than 5 times per hour are common in otherwise healthy subjects, particularly males and post-menopausal females, and are associated with minor changes in oxygen saturation. Longer periods of apnoea occurring more frequently, are the defining characteristic of the sleep apnoea syndromes [3], usually subdivided into patients who suffer intermittent upper respiratory tract obstruction and those who become apnoeic because of failure of central drive. Although described separately, there is often considerable overlap in individual patients. Characteristically, episodes of sleep disordered breathing are more common during rapid eye movement sleep. A minority of patients suffer such extreme disturbance of ventilation that diurnal respiratory and ultimately cardiac failure can result, and there is also an increased incidence of sudden death during sleep, almost certainly attributable to disturbances of cardiac rhythm associated with hypoxia.