AbstractContinuouspositiveairwaypressure(CPAP)isastandardtreatmentofmoderateandsevereobstructive sleepapnea syndrome.However, itseffect inpatients with coexistingobstructiveandcentralapneasiscontroversial. Objectives:TodeterminetheimmediateresponsetoCPAPincombinedobstructiveandcentralsleepapneapatientswithoutheartfailure. Methods:Thirty sevenconsecutivepatients with moderateandsevere coexisting obstructive andcentralapneas(combinedgroup)wereprospectivelyenrolledinthiscrosssectionalanalyticstudy.Allpatientsunderwentafullnight-attendedandafullnightCPAPtitrationpolysomnography.TitrationwasconsideredsuccessfulifAHI 10andthetitrationstudyincludedatleast15 min inREMstage. Results:OnCPAPtitration,thecombinedgroupshowedsignificantimprovementinsleepandrespiratorypolysomnographicparameters.MeanAHIwasreducedfrom71.9±30.3to 8.39±5.15(P=0.000).WhereasCPAPsignificantlyreducedthecentralapneaindexfrom 12.8±6.67to3.1±2.86(P=0.000),theresponsetocentraleventswasvariable(rangedfrom20%to100%).Overallresults,25(67.6%)hadsuccessfultitrationwithsignificantbetterresponseinfemalesthanmalestoCPAPthanmales(88.9%vs.60.7%,P=0.019). Conclusion:CPAPcanbeeffectiveincombinedobstructiveandcentralapneapatientswithoutheartfailurewithconsiderationofindividualvariability.AtrialofCPAPtitrationshouldbedoneinthosepatients. 2016TheEgyptianSocietyof ChestDiseasesandTuberculosis.Productionandhostingby ElsevierB.V.Thisisanopenaccessarticle under theCCBY-NC-ND license (http://creativecommons.org/licenses/by-nc-