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1、HypoxiaReviewofrespirationMeasurementsofO2Hypoxiadefinitionclassification,etiology,mechanismresultantchangesinthebodypreventionandtreatmentOverview1. O2 intake2. Hb carrying O23. O2 transport in circulation4. O2 utilization in the tissueRespiration-aprocessofgasexchangeExternal respiration O2depende
2、nceLargeamountofO2consumption-250ml/min(360L/day)SmallamountofO2storage-1.5L(sustainlifeonlysixminutes)Continuoushypoxia6min-life-threateningPO2(partialpressureofoxygen)血氧分压Oxygentension血氧张力thetensionproducedbyoxygenmoleculesphysicallydissolvedinthebloodArterial(PaO2):100mmHg(13.3kPa)，取决于吸入气体的氧分压和外呼
3、吸功能Venous(PvO2):40mmHg(5.33kPa)，取决于组织摄氧和用氧的能力Influencefactors(IFs):PressureofO2intheair（空气氧分压）Externalrespiratoryfunction（外呼吸功能）Shuntofblood( (血液分流) )MeasurementsofO2(1)CO2max(oxygenbindingcapacity)，最大血氧容量Maximalamountofoxygenthatcanbepotentiallyboundbythehaemoglobin(Hb),reflectingtheabilityofHbcarr
4、yingO2.Underidealcondition,thebindingcapacityis1.34ml/gHbCO2max反映血液携氧能力的强弱IFs:QuantityofHb( (血红蛋白的量) )QualityofHboraffinityofHb( (血红蛋白的质与亲和力) )MeasurementsofO2(2)CO2:(oxygencontent),实际血氧含量theactualO2contentintheblood,includingtheoxygenboundtotheHbandO2dissolvedintheblood.ArterialCO2(CaO2):19ml/dlVen
5、ousCO2(CvO2):14ml/dlDifferencesofCO2betweenarterialandvenous(Da-vCO2):动-静脉血氧含量差：5ml/dlIFs:PaO2CO2max-HbquantityandqualityMeasurementsofO2(3)SO2(oxygensaturation)，血氧饱和度thepercentageofoxygen-boundform(oxyhemoglobin)intotalHb.SO2=(血氧含量-溶解氧量)、血氧容量X100%Arterial(SaO2):97-99%Venous(SvO2):75%IFs:PO2pH,tempe
6、ratureCO2,DPGMeasurementsofO2(4)AcurvereflectingtherelationshipbetweenthePO2andSO2S(sigmoid)shapeSO2,SDCleftshiftHbaffinitySO2,SDCrightshiftHbaffinityO2saturationdissociationcurve(SDC)Right shiftLeft shiftP50:thePO250%SO2ReflectingtheflexibilityofHbcarryingO2SDCrightshift,P50SDCleftshift,P50P50-aval
7、ueindicatingtheflexibilityofHbHypoxiaDefintion:ApathologicalprocessinwhichO2supplytotissuesisinadequatetomeetthedemandofcells,orutilizationofO2isinsufficientincellsdespiteadequateO2supply,leadingtochangesinfunctions,metabolismsandstructuresofcellsandtissuesinthebody.Inadequate supply of O2 (氧供不足氧供不足
8、)Insufficient utilization of O2 （用氧障碍用氧障碍） 1. O2 intake2. Hb carrying O23. O2 transport in circulation4. O2 utilization in the tissueClassificationofhypoxia1. Hypotonic hypoxia2. Hemic hypoxia3. Circulatory hypoxia4. HistogenoushypoxiaThemostcommontypeofhypoxiaCauses:O2supplyTibetanPlateau,mineralwe
9、llsDysfunctioninexternalrespiration,a.k.arespiratoryhypoxiaBronchialobstructionRespiratorymuscleparalysisVenous-to-arterialshuntsCongenitalcardiacdefectsHypotonic/hypoxichypoxia(低张性缺氧)Features:minor:PaO2;CO2NSevere:PaO2;CO2maxN,CaO2;SaO2D(a-v)O2orNCentralcyanosis(紫绀)RespiratorycompensationHypotonic/
10、hypoxichypoxiaCyanosis(发绀或紫绀)Deoxyhemoglobin5g/dl(centralcyanosis)Patientswithhypoxiacanshowcyanosis,butcynosisdoesnotmeanhypoxia.Patientswithsevereanemia(贫血)，withtotalamountofhemoglobin1.5g/dl, 皮肤，粘膜可出现青紫，为皮肤，粘膜可出现青紫，为肠源性肠源性紫绀紫绀。Features:NormalPaO2CO2maxandCaO2O2deliverytotissueCO2maxnormalbutaffin
11、ityO2releasetotissueHemic/isotonichypoxiaInadequatebloodflowresultingininsufficientoxygenationofthetissueCauses:Generalcirculatorydysfunction-shock,heartfailureLocalcirculatorydysfunction-stenosis,occlusion,thrombosisMechanisms-tissueperfusionischemiahypoxia（缺血性缺氧）congestivehypoxia（充血性缺氧）Circulatory
12、/hypokinetichypoxia（循环性缺氧） Features: a. PaO2: N PvO2 b. CaO2: N CvO2 c. CO2max: N d. SaO2: N e. (Da-vCO2) f. Peripheral cyanosis (外周性紫绀外周性紫绀) g. Respiratory compensationCirculatory/hypokinetichypoxia（循环性缺氧）由于全身性或局部循环障碍使血液流经组织毛细血管的时间延由于全身性或局部循环障碍使血液流经组织毛细血管的时间延长，长， 细胞从单位容量血液中摄取的氧量增加，使静脉血氧含量细胞从单位容量血液中
13、摄取的氧量增加，使静脉血氧含量降低，动降低，动-静脉血氧分差增加静脉血氧分差增加Histogenous/dysoxidativehypoxia(组织性缺氧)Causes:Cell/tissuepoisoningcyanide(氰化物)poisoninghistotoxichypoxiaArsenicpoisoning(砒霜)Mitochondriainjuryradiation;ROSInadequatesynthesisofbiologicaloxidationcoenzymedeficiencyofvitaminB2orPPMechanisms:Aberrantbiologicaloxid
14、ationoroxidativephosphorylationdeficiencyinoxygenconsumptionATP. Features: a. PaO2 = N, PvO2 b. CaO2 = N, CvO2 c. CO2max = N d. SaO2 = N e. (CaO2-CvO2) f. No cyanosis g. No respiratory compensationFeatures of different types of hypoxia Type PaO2 SaO2 CO2 max CaO2 D(a-v)CO2Hypotonic hypoxia N or NHem
15、ic hypoxia N or N or N or N Circulatory hypoxia N N N N Histogenic hypoxia N N N N Notes: decrease; increase; N normal.Hypotonichypoxia:PaO2Hemichypoxia:NormalPaO2,alteredHbquantityandquality,CO2maxorCirculatoryhypoxia:NormalPaO2,Hbquantityandquality,bloodflowHistogenoushypoxia:normalO2supplytotheti
16、ssue,O2utilizationFeaturesofdifferenttypesofhypoxiaImpact of hypoxia on the bodySlight hypoxia: stimulationCompensatory responsesSevere hypoxia: impairmentdysfunction and failure of cells and tissuesAcute hypoxia: mainly damageChronic hypoxia: both damage and compensationRespiratory systemCirculator
17、y systemHematologic systemCentral nervous system Tissues and cellsCompensatory reaction-hyperventilation (过度通气过度通气) PaO2 8Kpa or 60 mmHg chemoreceptorsrespiratory rate and depth hypoxic ventilation reaction (HVR).Consequences:respiratory surface, O2 diffusion, PaO2&SaO2More fresh air into the lung,
18、PaO2 ，PCO2blood volume returning to the heartRespiratory system缺氧引起的过度通气其意义在于：缺氧引起的过度通气其意义在于：1.增加肺泡通气量和肺泡气的PO2(PAO2)，从而增加动脉血氧分压PO2(PaO2)2.胸廓运动增强，增大胸内负压，促进静脉回流、增加回心血量，继而增加心输出量和肺血流量， 有利于血液摄取和运输更多的氧肺通气量增加是急性低张性缺氧的最重要代偿方式。肺通气量增加是急性低张性缺氧的最重要代偿方式。Injury manifestationHigh-altitude pulmonary edemaRespirator
19、y failureSevere hypoxia (PaO2 30 mmHg) inhibition of respiratory center slow and periodic or irregular breathing stop of breathing.CirculatorysystemCompensatoryresponsesCardiacoutput:tachycardia（心动过速）arrhythmiamyocardialcontractilityPulmonaryvasoconstrictionpulmonaryarterialhypertensionrightheartfai
20、lureRedistributionofbloodensureenoughbloodtoheartandbrainCapillaryhyperplasiaInjurymanifestationPulmonaryhypertensionDecreaseddiastolicandsystolicmyocardialfunctionArrhythmiaDecreaseinVenousbloodreturntotheheart HemicsystemCompensatoryresponsesRightwardshiftofoxyhemoglobindissociationcurveIncreaseof
21、redbloodcellanderythropoietin(EPO)InjurymanifestationBloodviscosityBrain is highly sensitive to hypoxia. Blood redistribution to the brainPaO28 mmHg， mental disorder Cerebral edemaCentral nervous system CellCompensation:increasedabilitytouseO2anaerobicglycolysisincreaseofmyoglobinInjurymanifestation
22、cellularmembraneinjurymitochondriaimpairmentlysosomebreakageFactorsinvolvedintolerancetohypoxiaOxygenconsumptionrateBrainoxygenconsumptionratetoleranceSkinoxygenconsumptionratetoleranceCompensatoryabilityofthebody PreventionandtreatmentInhalationofoxygen(氧吸入)Efficiency:HypotonichypoxiathebestHistoge
23、noushypoxiatheworstWhenthepatientinhaledhighpressureofoxygen(PO2is2-3timesatmosphere),aseriesoftoxicsignsandsymptomswasappeared,thisconditionistermedasoxygentoxication（氧中毒）. Oxygen toxication: 1. Pulmonary oxygen toxication 2. Cerebral oxygen toxication The mechanisms of oxygen toxicity: Reactive oxygen species (氧自由基氧自由基) or oxygen free radicals .掌握各项血氧检测指标的意义。掌握各项血氧检测指标的意义。掌握缺氧概念，分类与特征。掌握缺氧概念，分类与特征。掌握紫绀，肠源性紫绀的概念。掌握紫绀，肠源性紫绀的概念。熟悉呼吸的基本过程。熟悉呼吸的基本过程。熟悉机体对缺氧的代偿反应熟悉机体对缺氧的代偿反应。熟悉缺氧治疗的原则。熟悉缺氧治疗的原则。了解氧中毒概念。了解氧中毒概念。学学 习习 目目 标标 与与 内内 容容Thank you !
