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

Abstract

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 obstructive sleep apnea (OSA), blood oxygen alteration, and hypercapnia may be more severe. We aimed to study hypoxemia 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 severe 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.

Keywords

• Nocturnal hypoxia
• Chronic obstructive pulmonary disease
• Sleep-disordered breathing
• Polysomnography