Breathing Pattern and Eye Movement Density during REM Sleep in Humans

Abstract

Changes in the density of eye movement during rapid eye movement (REM) sleep are associated with changes in ventilation and ventilatory response in animals. Recent data in patients with chronic obstructive pulmonary disease suggest that periods of frequent eye movements may be associated with hypoxemia during REM sleep. We have therefore investigated the association between eye movements and ventilation and ventilatory pattern in 10 normal men. Expired ventilation was measured using a pneumotachograph attached to a valved face mask with a dead space of 50 ml and incorporating a peripheral CO2 leak detector. Ventilation was reduced (p < 0.02) in all stages of sleep compared with that during wakefulness, with no difference between the level of ventilation in each sleep stage (awake, 7.18 .+-. 0.43 SEM: Stage 2, 6.47 .+-. 0.43; Stage 3/4, 6.45 .+-. 0.52; REM sleep, 6.55 .+-. 0.47 L/min). During REM sleep, eye movements (EMs) were associated with rapid shallow breathing. Dividing REM into 20-s epochs with or without EMs, EMs were associated with raised breathing frequency (no EMs, 14.4 .+-. 0.4 breaths/min; EMs, 15.8 .+-. 0.5 breathws/min; p = 0.01), reduced tidal volume (0.49 .+-. 0.03; Li 0.41 .+-. 0.03 L; p < 0.01), and reduced minute ventilation (6.87 .+-. 0.45 L; 6.27 .+-. 0.51 L; p = 0.01). Eye movements were associated with a shortened expiratory time (2.44 .+-. 0.08 s; 2.20 .+-. 0.12 s; p < 0.05), an increased duty cycle ratio (TI/Ttot, 43.2 .+-. 0.9%; 45.7 .+-. 1.0%; p < 0.01), and reduction of mean inspiratory flow rate (0.27 .+-. 0.02 L/s; 0.24 .+-. 0.02 L/s; p < 0.02). Thus, ventilation was reduced during periods of dense eye movements in these men. Hypoventilation during periods of frequent EMs may explain the hypoxemia seen during REM sleep in patients with respiratory diseases.