Sleep induced hypoxemia in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease is a leading cause of morbidity and mortality worldwide. Sleep-induced hypoxemia is defined as "an SpO2 (oxyhemoglobin saturation) during sleep of < 90% for more than five minutes with a nadir of at least 85%" or "> 30% of total sleep time with an SpO2 of < 90%" in subject with a baseline awake SpO2 of ≥ 90%. Patients with moderate or severe COPD run a high risk of developing SIH mainly because of alveolar hypoventilation and ventilation-perfusion mismatch. Compared to their non-SIH brethren, SIH COPD patients have greater degrees of pulmonary hypertension and cor pulmonale, require more frequent hospitalizations, and sustain higher mortality rates. And the necessity of treatment of isolated SIH in COPD has been debated for years. In this mini review, the definition, reasons, prevalence, clinical significance and treatment approaches of SIH in COPD are summarized.