Sleep in patients with chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) become hypoxemic during sleep, particularly during rapid eye movement (REM) sleep. Those who are most hypoxemic when awake experience the most severe hypoxemia during sleep. The major cause of REM hypoxemia is hypoventilation, with additional contributions from alteration in ventilation/perfusion matching and functional residual capacity (FRC) reduction. REM hypoxemia probably contributes to the development of pulmonary hypertension and polycythemia and may predispose to cardiac arrhythmias in some patients. The most effective form of therapy is nocturnal oxygen therapy, but the indications for the use of nocturnal oxygen therapy are entirely based on daytime oxygenation levels. Routine polysomnography is not indicated in patients with COPD but should be performed in patients who have symptoms suggestive of coexisting sleep apnea/ hypopnea syndrome.