心肺交互作用(simplified)（五月二十六）.ppt

心肺交互作用 首都医科大学北京朝阳医院李文雄 Basicphysiologyofheart lunginteraction Pumpfunction PreloadatagivenHRPraorCVPAfterloadContractility Returnfunction Bloodvolume vein stressedandunstressedComplianceResistance CO Preload 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 ThisdecreaseinRVpreloadleadstoadecreaseinRVoutputthatsubsequentlyleadstoadecreaseinleftventricularoutput Second RVafterloadincreasesduringinspirationbecausetheincreaseinalveolarpressureisgreaterthantheincreaseinpleuralpressure However leftventricularpreloadin creasesduringinsufflationbecausebloodisexpelledfromthecapillariestowardtheleftatrium Finally leftventricularafterloaddecreasesduringinspirationbecausepositivepleuralpressuredecreasestheintracardiacsystolicpressureandthetransmuralpressureoftheintrathoracicpartoftheaorta CCM 2009 Ventricularafterload Definition theforceopposingejectionVentricularafterloadisrepresentedbytheleveloftransmuralpressure inthecourseofsystole withineithertheaorticroot LVafterload orthepulmonaryarterytrunk RVafter load Thetransmuralratherthantheintraluminalpressuremustbeconsideredbecausethesegreatvesselsaswellastheventriclesareexposedtoanextramuralpressure i e ITP whichisusuallynonatmospheric ThemechanismswherebyrespirationinteractswithLVandRVafterloadaredifferent LVafterload Attheonsetofspontaneousinspiration theintraluminalpressureintheaorticrootdecreaseslessthandoesITP duetotheconnectionofthisvesselwithextrathoracicarteries Asaresult aortictransmuralpressureincreases Withspontaneousbreathingtherefore LVafterloadisgreaterininspirationthaninexpiration AsymmetricalchainofeventsleadstoareducedLVafterloadinthecourseofatransientincreaseinITP suchaswithpositivepressureinflationofthelungs SteadyincreasesinITP aseffectedwithPEEP similarlyunloadtheLVwithpotentiallybeneficialconsequencesinpresenceofleftheartfailure asdescribedingreaterdetailbelow Sect EffectsofPEEPoncardiacoutput inPartII Conversely patientswithobstructivesleepapneahaveboutsofgreatlynegativeITPwhichincreaseLVafter load thuscontributingtoLVhypertrophy RVafterload AseminalpaperbyPermuttshowsthatRVafterloadishighlydependentonandincreaseswiththeproportionoflungtissueinWestzone1or2 asopposedtozone3conditions Zones1or2existwhenevertheextraluminalpressureofalveolarcapillaries whichisclosetoalveolarpressure PA exceedstheintraluminalvalue leadingtovesselcompression Inzone3bycontrast intraluminalcapillarypressureexceedsPAForhydrostaticreasons zones1and2aremorelikelytooccurinnondependentpartsofthelung Furthermore respiratorychangesintheintraluminalpressureofalveolarcapillariestendtotrackchangesinITPandthustodecreasemorethandoesPAduringaspontaneousinspirationandtoincreaselessthandoesPAoninflationofthelungwithpositivepressure Thus anyincreaseinlungvolume whetherinthecontextofspontaneousormechanicallyassistedbreathing hasthepotentialtopromotetheformationofzones1and2attheexpenseofzone3 andthustoincreaseRVafterload Theseconsiderationsareofhighclinicalrelevance notablyconcerningthepossibleinductionoraggravationofacutecorpulmonalebymechanicalventilation asdescribedbelow Sect Mechanicalven tilationandacutecorpulmonale inPartII IntensiveCareMed 2009 35 45 54 Afterload effectoflunginflation 肺膨胀影响CO肺膨胀挤压肺泡内血管肺膨胀必须增加胸膜腔内压Pv PA时影响很小 Zonesofthelung Zone1 PA Pa PvZone2 Pa PA PvZone3 Pa Pv PA Thezonesofthelungdividethelungintothreeverticalregions basedupontherelationshipbetweenthepressureinthealveoli PA inthearteries Pa andtheveins Pv Zonesofthelung 肺动脉和静脉压力与肺部区域有关肺尖最低肺底最高直立位肺顶部Pa很可能低于PA WestJ DolleryC NaimarkA 1964 Distributionofbloodflowinisolatedlung relationtovascularandalveolarpressures JApplPhysiol19 713 24 Zonesofthelung 全肺PA 0 2cmH2O直立位肺尖与肺底动脉压差 20mmHg受重力影响全肺静脉压 5mmHg肺尖部静脉压 5mmHg肺底部静脉压 15mmHgPAP 25 10mmHg Mean 15mmHg 肺尖部mPAP 5mmHg肺底部mPAP 25mmHg Zonesofthelung 正常人群全部肺区Pa PAZone1正常情况下不存在正压通气时可以存在PA Pa受肺泡压力影响区域血管彻底塌陷血流消失死腔通气 Zonesofthelung Zone2位于心脏上方3cm以上肺区区域血流呈搏动状毛细血管床静脉端阻塞 无血流动脉端压力超过PA时产生血流如此反复循环正常肺大部分位于Zone3存在连续血流zone1通气 血流比 zone3 Zonesofthelung PA Pv WestzoneII肺区 右室后负荷随肺膨胀增加随肺泡压1 1增加肺血管血流淤滞 肺水 Therelationbetweenlungvolumeandthepulmonaryvascularresistance Aslungvolumeincreasesfromresidualvolume RV tototallungcapacity TLC thealveolarvesselsbecomeincreasinglycompressedbythedistendingalveoli andsotheirresistanceincreases whereastheresistanceoftheextra alveolarvessels whichbecomelesstortuousaslungvolumeincreases falls Thecombinedeffectofincreasinglungvolumeonthepulmonaryvasculatureproducesthetypical Ushaped curveasshown withitsnadir oroptimum ataroundnormalfunctionalresidualcapacity FRC WhittenbergerJL etal JApplPhysiol1960 15 878 82 Frank Starlingrelationshipsbetweenventricularpreloadandstrokevolume Agivenchangeinpreloadinducesalargerchangeinstrokevolumewhentheventricleoperatesontheascendingportionoftherelationship A co。