Background: Compliance with fixed-level continuous positive airway pressure (CPAP) is similar whether the chosen pressure is derived by auto-titration or by attended manual titration, although the pressure derived from auto-titration is usually 2-5 cmH2O higher than manual titration.
Research question: If small changes in CPAP level do not influence preference, can complex CPAP titration procedures be simplified?
Study design: This study consisted of a series of physiological observations during wakefulness and a clinical trial at night. Diaphragm EMG, expiratory muscle EMG (transversus abdominis), and expiratory reserve volume (ERV) were measured in 12 healthy subjects at different CPAP levels. Breathing difficulty was assessed using a customized questionnaire in 35 healthy subjects and 33 patients with obstructive sleep apnea (OSA) at different CPAP pressures between 4 and 20cmH2O (with an increment of 2cmH2O). A two-night randomized crossover double-blind CPAP treatment study was also performed on 25 patients with OSA, using a pressure of 10cmH2O or the pressure derived from manual titration.
Results: In general, diaphragm EMG increased with increasing CPAP levels when CPAP was >10 cmH2O. Expiratory muscles were usually not obvious when CPAP level <14 cmH2O. End expiratory lung volume increased significantly with increasing CPAP level, but there was no significant difference in subjective sensation at different CPAP levels when pressure was <10 cmH2O or less. Sleep structure, AHI, and patient preference under the CPAP at 10 cmH2O were similar to that experienced at a pressure chosen by manual titration.
Conclusion: The majority of patients with OSA can be directly treated by CPAP at 10cmH2O without pressure titration.