Randomised, sham-placebo, parallel study of Nasal Continuous Positive Airway Pressure (NCPAP) for the treatment of Obstructive Sleep Apnoea (OSA)

Doubt has been expressed as to the true symtomatic benefit derived from NCPAP in patients with OSA. We are carrying out a randomised, sham placebo-controlled trial. Patients are recruited who have more than 10/hr >4%SaO2 dips, and Epworth sleepiness scores (ESS) of more than 9. Initial assessment includes the ESS (range 0-24) and a behavioural maintenance of wakefulness test (OSLER test, J.Sleep Res. 1997;6:142, range 0-40mins). Patients are told we are comparing two pressures for treating OSA, either of which may work. Following randomisation, patients are either auto-titrated with a DeVilbiss Horizon or receive a low fixed pressure. Thereafter they spend 4 weeks set at either their required titration pressure, or at <2cms H2O (achieved by adjusting the pressure setting to 3cmsH2O and providing extra air leaks at the mask). At 4 weeks the assessments are repeated blind and patients retitrated to their required levels. 100 patients have so far been randomised and 91 have completed the protocol. Results are medians and 25/75th centiles, significance by Wilcoxon rank sum tests. Pre Post Pre Post Significance of Real Real Placebo Placebo changes produced by real v placebo ESS 16 7 16 14 <0.001 13-19 4-9 13-18 7-16 OSLER 22 36 20 24 <0.003 mins 13-32 22-40 12-32 15-35. Compliance over the 4 weeks was 5.4 and 4.2 hrs/night, real and placebo respectively (P=0.02). Despite a small placebo effect there is clear significance in favour of active treatment