Valsalva meaningValsalva maneuver ruptured eardrumValsalva testvalsalva maneuver迷走神經Valsalva maneuver heart ratevalsalva maneuver心跳valsalva動作Valsalva maneuver pronunciationValsalva ratioValsalva maneuver PSVTvalsalva maneuver活動Valsalva maneuver mechanism

Hemodynamics of a Valsalva Maneuver - Cardiovascular ...

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Hemodynamics of a Valsalva Maneuver ... When a person forcefully expires against a closed glottis, changes occur in intrathoracic pressure that dramatically ...   Introduction Acknowledgements Topics: Arrhythmias CardiacValveDisease CoronaryArteryDisease Edema HeartFailure Hypertension Hypotension PeripheralArteryDisease AlsoVisitCVpharmacology.com ClickhereforinformationonCardiovascularPhysiologyConcepts,3rdedition,atextbookpublishedbyWoltersKluwer(2021) ClickhereforinformationonNormalandAbnormalBloodPressure,atextbookpublishedbyRichardE.Klabunde(2013)   Tweet HomeContentsTutorials/QuizzesGlossarySearchAuthor HemodynamicsofaValsalvaManeuver   Whenapersonforcefullyexpiresagainstaclosedglottis,changesoccurinintrathoracicpressurethatdramaticallyaffectvenousreturn,cardiacoutput,arterialpressure,andheartrate.ThisforcedexpiratoryeffortiscalledaValsalvamaneuver.InitiallyduringaValsalva,intrathoracic(intrapleural)pressurebecomesverypositiveduetocompressionofthethoracicorgansbythecontractingribcage.Thisincreasedexternalpressureontheheartandthoracicbloodvesselscompressesthevesselsandcardiacchambersbydecreasingthetransmuralpressureacrosstheirwalls.Venouscompression,andtheaccompanyinglargeincreaseinrightatrialpressure,impedesvenousreturnintothethorax.Thisreducedvenousreturn,andalongwithcompressionofthecardiacchambers,reducescardiacfillingandpreloaddespitealargeincreaseinintrachamberpressures.ReducedfillingandpreloadleadstoafallincardiacoutputbytheFrank-Starlingmechanism.Atthesametime,compressionofthethoracicaortatransientlyincreasesaorticpressure(phaseI);however,aorticpressurebeginstofall(phaseII)afterafewsecondsbecausecardiacoutputfalls.Changesinheartratearereciprocaltothechangesinaorticpressureduetotheoperationofthebaroreceptorreflex.DuringphaseI,heartratedecreasesbecauseaorticpressureiselevated;duringphaseII,heartrateincreasesastheaorticpressurefalls. Whenthepersonstartstobreathenormallyagain,aorticpressurebrieflydecreasesastheexternalcompressionontheaortaisremoved,andheartratebrieflyincreasesreflexively(phaseIII).Thisisfollowedbyanincreaseinaorticpressure(andreflexdecreaseinheartrate)asthecardiacoutputsuddenlyincreasesinresponsetoarapidincreaseincardiacfilling(phaseIV).Aorticpressurealsorisesabovenormalbecauseofabaroreceptor,sympathetic-mediatedincreaseinsystemicvascularresistancethatoccurredduringtheValsava.Similarchangesoccurwheneverapersonconductsaforceexpirationagainsteitheraclosedglottisorhighpulmonaryoutflowresistance,orwhenthethoracicandabdominalmusclesarestronglycontracted.Thiscanoccurwhenapersonstrainswhilehavingabowelmovement. Similarchangescanalsooccurwhenapersonliftsaheavyweightwhileholdingtheirbreath.Revised4/28/2014 DISCLAIMER:Thesematerialsareforeducationalpurposesonly,andarenotasourceofmedicaldecision-makingadvice.

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