Continuous positive airway pressure in clinically stable patients with mild-to-moderate obesity hypoventilation syndrome and obstructive sleep apnoea.

Background and objective The use of continuous positive airway pressure (CPAP) treatment in patients with obesity hypoventilation syndrome (OHS) and obstructive sleep apnoea (OSA) was evaluated, and factors that might predict CPAP treatment failure were determined. Methods A sleep study was performed in 29 newly diagnosed, clinically stable OHS patients. CPAP treatment was commenced if the apnoea–hypopnoea index was >15. Lung function, night-time oximetry, blood adipokine and C-reactive protein levels were assessed prospectively on enrollment and after 3 months. Treatment failure at 3 months was defined as daytime arterial partial pressure of carbon dioxide (PaCO2) >45 mm Hg and/or oxygen saturation (SpO2) 30% of the night-time oximetry study. Results All patients had severe OSA (median apnoea–hypopnoea index = 74.7 (62–100) with a nocturnal mean SpO2 of 81.4 ± 7), and all patients were treated with CPAP. The percentage of time spent below 90% saturation improved from 8.4% (0.0–39.0%) to 0.3% (0.4–4.0%). Awake PaCO2 decreased from 50 (47–53) mm Hg to 43 (40–45) mm Hg. Seven patients failed CPAP treatment after 3 months. PaCO2 at 1 month and mean night-time SpO2 during the first night of optimal CPAP were associated with treatment failure at 3 months (odds ratio 1.4 (1.03–1.98); P = 0.034 and 0.6 (0.34–0.93); P = 0.027). Conclusions CPAP treatment improves night-time oxygenation and daytime hypoventilation in selected clinically stable OHS patients who also have OSA. Patients with worse night-time saturation while on CPAP and higher daytime PaCO2 at 1 month were more likely to fail CPAP treatment.