Determinants of breathing effort sensation in normoxia and hypobaric hypoxia

Abstract

none13Thesensationofbreathingeffortisthoughttobetheresultofacomplexintegra- tion ofdifferentsensoryinputsincludingchemical-,mechanical- andneural-based signals.Wewishedtoexplorethedeterminants ofbreathingeffortsensation(BES) duringexhaustingexerciseinnormobaricnormoxiaandhypobarichypoxia.Eleven non-smokinghealthymalesubjects(age41[14],mean[SD]yr)werestudiedduring incrementalcycleexercise(30watt/3min)untilexhaustion(WLmax)atsealevel (SL)andafter2-3daysat4559meters(ALT).WemeasuredBES(Borgscale), ventilation(V’E),tidalvolume(Vt),respiratoryrate(RR),oxygensaturation(Sat), workofbreathing(fromdynamicesophagealpressure-volumeloops,WOB),total breathingmechanicalpoweroutput(W’=WOB*RR)andenergycostofbreathing perunitventilation(WOB/V’E). ComparedtoSL,atALTV’EandSatwerehigher(p<0.001forboth)foranywork- load.WLmaxwas15[8]%lowerthanSL(p<0.001).TheBESvsV’Erelationship wassimilaratALTcomparedtoSL.WithincreasingV’E,W’wasprogressively loweratALTthanatSL(p<0.001)asaconsequenceofaprogressivelyreduced flowresistivework.BeyondV’E>∼50 L/minBESwasprogressivelyhigherat ALTcomparedtoSLforagivenWOB/V’E.Yet,thechangesofVtandRR remainedsimilaratanylevelofventilationonbothconditions. In conclusionbreathingeffortsensationappearsuniquelyrelatedtoventilation, despitethedifferencesincostofbreathingandmetabolicrequirementsatALTand SL.noneA.Aliverti; A.LoMauro; M.Quaranta; P.Pompilio; R.Dellacà; M.Milanese; L. Pomidori ; L. Cavalleri; V. Fasano; A. Cogo; R. Pellegrino ; B. Kayser; G. MiserocchiA., Aliverti; A., Lomauro; M., Quaranta; P., Pompilio; R., Dellacà; M., Milanese; Pomidori, Luca; L., Cavalleri; V., Fasano; Cogo, Annaluisa; R., Pellegrino; B., Kayser; G., Miserocch