Influence of sleep on respiratory function in emphysema.

To assess the influence of sleep on respiratory function, five patients with chronic obstructive pulmonary disease (COPD) with laboratory evidence of emphysema were monitored during sleep in a horizontal body plethysmograph. Neither lung volume nor lower airway resistance (Rla) changed in association with sleep. Upper airway resistance (Rua) increased during sleep and was highest during rapid eye movement (REM) sleep (Rua = 5.9 +/- 1.1, 9.6 +/- 2.1, 11.2 +/- 1.5, and 15.6 +/- 4.1 cm H2O/L/s during wakefulness, Stages 2, 3-4, and REM, respectively, p < 0.05). Tidal volume (VT) decreased during sleep, resulting in a sleep-associated decrement in minute ventilation (VI = 8.69 +/- 0.46, 7.64 +/- 0.65, 7.08 +/- 0.70, and 5.62 +/- 0.47 L during wakefulness, Stages 2, 3-4, and REM, respectively, p < 0.05). Respiratory neuromuscular output was also reduced during sleep (esophageal occlusion pressure [P0.1] = 2.69 +/- 0.39, 2.02 +/- 0.27, 1.90 +/- 0.27, and 1.63 +/- 0.25 cm H2O during wakefulness, Stages 2, 3-4, and REM, respectively, p = 0.005). We conclude that in patients with emphysema (1) sleep does not alter lung volume or increase lower airway resistance, (2) sleep is associated with a decrease in VT and VI, and (3) sleep is associated with an increase in Rua and a reduction in P0.1 that may contribute to the sleep-associated decrease in VI.