Chronic Obstructive Pulmonary Disorders (COPD) and Sleep

Abstract

Alveolar hypoventilation and alterations in the distribution of ventilation perfusion ratios are the predominant mechanisms of hypoxemia during sleep with related transient episodes of pulmonary hypertension. We study, by all night polysomnography, 17 patients with severe chronic obstructive pulmonary diseases (mean awake PaO₂ 9 KPa, mean FEV, 30 per cent predicted normal). Preliminary data show that only 5 subjects had significant episodes of apnea during sleep. We did not find the cyclic precipitous falls in SaO₂ so characteristics of sleep apnea syndrome, althought in 14 patients (82%) there are sleep disturbances (especially during REM sleep). We think that the majority of patients with COPD do not have the classical sleep apnea syndrome. Furthermore, since the frequency of arousal does not decrease significantly following nocturnal oxygen therapy, we emphasize that, in our study, the 5 patients with sleep apnea syndrome, had also the higher PaCO₂. It could be possible that not hypoxemia, but hypercapnia is the principal arousal stimulus.