Sixteen patients—one woman and 15 men—aged 51±9 years (mean±standard deviation), body mass index (BMI) 33±8 kg/m2, apnea/hypopnea index at diagnosis 50±28/h, on long term nasal CPAP therapy (pressure: 10.7±2.1 cm H2O) were examined. We titrated lowest pressure needed was 5.9±2.3 cm H2O, the highest 10.8±3 cm H2O. With the exception of two cases, maximum pressure was necessary during REM and when the patient was in the supine position. Statistical analysis revealed that the required CPAP level was significantly higher in the supine position than in the lateral position (p=0.02). Manual regulation of pressure did not increase the number of arousals. The observed variations in the "splinting" pressure required supports the use of nasal CPAP devices with auto-titration rather than constant pressure CPAP devices.