Background: Patients with OSA are usually treated by automatic CPAP or Fixed CPAP after pressure titration. However, we have previously shown that auto-titrated CPAP was usually 2-5 cmH2O higher than the manual titrated pressure, suggesting patients whose auto-titrated CPAP higher than 10 cmH2O could still be treated by the fixed CPAP at 10 cmH2O.

Methods: Twenty-one severe OSA patients (age 44±11 years, BMI 30.3±5.2 kg/m2, AHI 74.8±13.8 events/h) whose 90% of automatic pressure ?11 cmH20 (mean titrated pressure 13.1±1.9 cmH20) were invited to have an overnight full polysomnography under the fixed CPAP level of 10 cmH2O.  

Results: The residual AHI in two subjects whose AHI before treatment was 67 events/h and 86 events/h was still unnormal and was 14 events/h and 20 events/h respectively.  However, the residual AHI in all other subjects under fixed CPAP at 10 cmH2O was lower than 10 events/h.  There were no significant differences in AHI between Auto-CPAP and fixed CPAP at 10cmH20 ( 4.3±1.8 events/h vs 3.2±3.3 events/h; p>0.05). The number of patients who preferred to be treated by Auto-CPAP was similar to by fixed CPAP at 10cmH2O (?2 = 1.322, P>0.05). 

Conclusions: A fixed CPAP at 10 cmH2O can be used to treat most severe patients even whose auto titrated pressure is  higher than 10 cmH2O.