Fixed CPAP at 10 cmH₂O May Replace Manual Titration in Moderate to Severe OSA Patients: A Preliminary Randomised Controlled Trial

Background and Objectives: Patient compliance with continuous positive airway pressure (CPAP) is similar using manual-titrated pressure compared to auto-titration, although auto-titration pressures are usually 2–5 cmH₂O higher than manual pressure, indicating that CPAP moderately higher than the optimal pressure will not necessarily impair compliance. We try to find the tolerable highest CPAP which does not increase respiratory effort based on changes in lung volume, diaphragm electromyography (EMG) and breathing sensations in healthy volunteers and OSA patients to simplify pressure titration. Methods: Part 1, 12 healthy subjects and 16 OSA patients were enrolled in the measurement of expiratory reserve volume, diaphragm EMG, and expiratory muscle EMG at different CPAP levels. Breathing difficulty during different CPAP levels was assessed using a customised questionnaire in 35 healthy subjects and 33 OSA patients. Part 2, a two-night randomised crossover double-blind trial using the tolerable highest CPAP (10 cmH₂O) based on the results derived from Part 1 and the manually titrated pressure was performed in 25 OSA patients. Results: End expiratory lung volume increased significantly with increasing CPAP. In general, diaphragm EMG changed little when CPAP ≤ 10 cmH₂O. Expiratory muscle activity appeared when CPAP > 12 cmH₂O. There was no significant difference in subjective sensation of breathing difficulty with CPAP ≤ 10 cmH₂O. Sleep structure, AHI, and patient preference with 10 cmH₂O CPAP were not different from those under titrated pressure. Conclusions: This study suggests that most patients with moderate to severe OSA can be effectively treated with CPAP at an initial pressure of 10 cmH₂O without pressure titration.