[Effect of sleep on respiration]

Physiologists as well as chest physicians are both interested in respiratory control and disturbances during sleep. Many studies have demonstrated episodic falls in oxygen saturation in lung disease during sleep related to episodic alveolar hypoventilation and/or apneas. A better understanding of these sleep-induced disorders has been possible since the use of electroencephalo-and oculogram (EEG-EOG) to separate the two stages of sleep i.e rapid eye movement sleep (REM sleep) and slow wave sleep (non-REM sleep), and of non invasive methods in assessment of respiratory parameters. Several mechanisms may explain respiratory disturbances during sleep: --a failure of respiratory control systems which differ between the two stages of sleep (central apnea); --a decrease in activity of all upper airway muscles, mainly during REM sleep (occlusive apnea); --a worsening in ventilation-perfusion inhomogeneities which may occur independently of the apnea periods. The detection of such falls in oxygen saturation in pulmonary patients, especially in hypoxemic ones appear to be very important to avoid the adverse effects of hypoxemia on pulmonary circulation. This could be realized by: --an evaluation of respiratory disorders during sleep; --a better assessment of the respiratory control systems in cold patients; --suppression of predisposing factors of occlusive apnea. These different investigations would lead us to a more logical management of respiratory disturbances during sleep, especially in patients suffering from chronic respiratory insufficiency.