A Comparison of Nocturnal Hypoxia Markers in Apnea Patients with Chronic Obstructive Pulmonary Disease and without it: A Crosssectional Study

Background and Objective: The main causes of nocturnal hypoxemia are pulmonary diseases or sleep related breathing disorders. In overlap syndrome, the co-existence of chronic obstructive pulmonary disease (COPD) and ob-structive sleep apnea (OSA), blood oxygen alteration, and hypercapnia may be more severe. We aimed to study hypox-emia markers in OSA patients with or without COPD. Materials and Methods: This cross-sectional study evaluated clinical data and polysomnographic findings of 210 patients with apnea hypopnea index (AHI) 5 among whom 35 patients had COPD. Results: A total of 210 patients with mean age of 57 years were enrolled in this study. 140 patients (66.7%) had se-vere OSA (AHI ≥ 30). At wake stage, the mean oxygen saturation (SpO2) was 89.7 ± 5.1 mmHg for those with severe apnea, 91.0 ± 5.7 mmHg for non-severe apnea patients (AHI 30), 82.7 ± 10.1 mmHg for COPD patients with severe apneas, and 89.3 ± 7.5 mmHg for COPD patients with non-severe OSA (P 0.0001). Mean pressure of carbon dioxide was 52.9 ± 7.6 mmHg for COPD patients with severe apneas, and 50.2 ± 10.1 mmHg among those with not-severe OSA (P 0.0001). In average, blood SpO2 dropped to 68.0 ± 12.6 mmHg in severe OSA group, to 57.0 ± 13.6 mmHg in COPD patients with severe OSA (P 0.0001). Conclusion: Hypoxemia is significantly prominent in overlap syndrome. The presence of diurnal hypoxemia and hypercapnia may predict nocturnal hypoxemia in these patients.