Chronic Obstructive Pulmonary Disease
Both hypoxemia and hypercapnia can develop during sleep in patients with chronic obstructive pulmonary disease. Respiratory impairment is more severe during REM sleep compared with NREM sleep. Hypoxemia, the extent of which is related to the percentage of REM sleep in relation to total sleep time and daytime levels of PaCO2, PaO2, and oxygen saturation (SaO2), can result from hypoventilation, ventilation-perfusion mismatching, or reduction of lung volume (eg, functional residual capacity). Chronic obstructive pulmonary disease can also occur concurrently with obstructive sleep apnea; referred to as the ‘‘overlap syndrome,’’ this is associated with worse hypoxemia and greater pulmonary artery pressures compared with patients with isolated chronic obstructive pulmonary disease.
Source : Respiratory Disorders and Sleep, An Issue of Sleep Medicine Clinics (The Clinics: Internal Medicine)
