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ID:50572307
大小:4.39 MB
页数:66页
时间:2020-03-11
《心肺交互作用simplified.ppt》由会员上传分享,免费在线阅读,更多相关内容在工程资料-天天文库。
1、心肺交互作用首都医科大学北京朝阳医院李文雄Basicphysiologyofheart–lunginteractionPumpfunction:PreloadatagivenHRPraorCVPAfterloadContractility.Returnfunction:Bloodvolume(vein)stressedandunstressedComplianceResistanceCOPreload—Transmuralpressure跨壁压(Ptm)舱或血管内外压力差=血管内收缩压−Ppl非胸腔内血管外压=大气压(传感器的零点)胸腔内血管被胸膜腔内压包围胸膜
2、腔内压随通气周期变化Ppl↑→RV前负荷↓自主呼吸或负压呼吸时Ppl和血管内主动脉压力均下降Ppl下降幅度大于主动脉压力下降幅度Ptm实际增加→LV后负荷↑、SV↓FourmechanismsparticipateinthecyclicchangesofSVobservedduringmechanicalventilation.First,duringinsufflation,venousreturndecreasesduetoanincreaseinpleuralpressure.ThisdecreaseinRVpreloadleadstoadecreasei
3、nRVoutputthatsubsequentlyleadstoadecreaseinleftventricularoutput.Second,RVafterloadincreasesduringinspirationbecausetheincreaseinalveolarpressureisgreaterthantheincreaseinpleuralpressure.However,leftventricularpreloadin-creasesduringinsufflationbecausebloodisexpelledfromthecapillarie
4、stowardtheleftatrium.Finally,leftventricularafterloaddecreasesduringinspirationbecausepositivepleuralpressuredecreasestheintracardiacsystolicpressureandthetransmuralpressureoftheintrathoracicpartoftheaortaCCM.2009VentricularafterloadDefinition:theforceopposingejectionVentricularafter
5、loadisrepresentedbytheleveloftransmuralpressure,inthecourseofsystole,withineithertheaorticroot(LVafterload)orthepulmonaryarterytrunk(RVafter-load)Thetransmuralratherthantheintraluminalpressuremustbeconsideredbecausethesegreatvesselsaswellastheventriclesareexposedtoanextramuralpressur
6、e(i.e.,ITP)whichisusuallynonatmospheric.ThemechanismswherebyrespirationinteractswithLVandRVafterloadaredifferent.LVafterloadAttheonsetofspontaneousinspiration,theintraluminalpressureintheaorticrootdecreaseslessthandoesITP,duetotheconnectionofthisvesselwithextrathoracicarteries.Asares
7、ult,aortictransmuralpressureincreases.Withspontaneousbreathingtherefore,LVafterloadisgreaterininspirationthaninexpiration.AsymmetricalchainofeventsleadstoareducedLVafterloadinthecourseofatransientincreaseinITP,suchaswithpositivepressureinflationofthelungs.SteadyincreasesinITP,aseffec
8、tedwithPEEP,
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