ABSTRACT
Not only is the voluntary control of respiration seen in the awake state lost with the emergence of sleep, the usual ventilatory responses to both low oxygen and high carbon dioxide levels are also blunted (25-28). The marked hypoxemia seen during REM sleep in patients with severe lung and chest disease is due to this phenomenon, which is most depressed during REM sleep. These physiological responses may also be important in the pathogenesis of upper airway obstruction during sleep and are responsible for the patient’s failure to arouse rapidly during apneas or hypopneas. The change in ventilatory sensitivity to external stimuli during sleep therefore predisposes patients with airway problems to develop clinically significant hypoxia and hypercapnia before arousal occurs.
