Is more NCPAP better?

Study objectivesTo assess the benefit of NCPAP in OSA and its relation to the degree of use of NCPAP.DesignRandomised parallel controlled one month study comparing NCPAP set at therapeutic levels of pressure, with NCPAP set at sub-therapeutic pressure levels.SettingTeaching hospital sleep clinic and laboratorySubjects101 men referred for investigation of possible OSA who were sleepy (Epworth Sleepiness Score > or = 10) and had > or = 10/hr of >4% dips in SaO2 due to OSA.Outcome measuresBaseline and one month measures of Epworth Sleepiness Score (ESS), Maintenance of Wakefulness Test (MWT), and the Energy/Vitality dimension of the SF-36 (health status questionnaire). Correlation of these outcome measures with NCPAP usage.ResultsAll outcome measures improved significantly more in the therapeutic, compared to the sub-therapeutic, group (e.g. ESS 15.0 to 13.0 on sub-therapeutic, and 15.5 to 7.0 on therapeutic, p<1x10(-6)). The degree of improvement correlated significantly with NCPAP usage in the therapeutic group (ESS, r=-0.60; MWT, r=0.55) but insignificantly in the sub-therapeutic group (ESS, r=-0.15; MWT, r=-0.06). Sub-therapeutic NCPAP did not improve OSA severity and acted as a control.ConclusionsNCPAP is clearly effective in relieving the sleepiness of OSA compared to a control group identical in every way, except for receiving a nasal pressure inadequate to control the OSA.