[Breathing during sleep].

Sleep alters breathing pattern and respiratory responses to many external stimuli. These changes permit the development of sleep-related hypoxemia in patients with respiratory diseases and may contribute to the pathogenesis of apneas in patients with sleep apnea syndrome. Many respiratory problems during sleep are related to an abnormal control of ventilation. The impaired ventilatory responses permit the development of hypoventilation during sleep and of sleep-related hypoxemia in patients with hypoxic chronic emphysema post TB sequela and kyphoscoliosis. In all these conditions, the hypoxia is most marked in REM sleep, when the ventilatory responses are at their lowest. The impaired ventilatory responses during sleep may accompanied by a decrease in the response of the upper airway opening muscles to chemostimulation during sleep and both factors may be important in the initiation and continuation of apneas.