Effects ofpostureon carbon dioxide responsiveness inpatients withobstructive sleep

isweilknownthatupper airwayresistance increases withpostural changefroma sitting tosupineposition inpatients withobstructive sleep apnoea (OSA).Itisnotknown,however, howthe postural changeaffects theventilatory and occlusion pressureresponseto hypercapnia inpatients withOSA when awake. Methods-Theresponsesof minute ventilation (VE)andmouthpressure 0-1 seconds after theonsetofoccluded inspi- ration(P0.,) toprogressive hypercapnia (A&EIAPco2, APO.5/APco2) bothinsitting andsupine positions weremeasuredin20 patients withOSA.Theratioofthetwo (AVEIAPO.,) wasobtained asan indexof breathingefficiency. The postural