基础医学各论I：缺氧-病生

1、HypoxiaReview of respirationReview of respirationMeasurements of OMeasurements of O2 2HypoxiaHypoxiadefinitiondefinitionclassification, etiology, mechanismclassification, etiology, mechanismresultant changes in the bodyresultant changes in the bodyprevention and treatmentprevention and treatmentOver

2、view1. O2 intake2. Hb carrying O23. O2 transport in circulation4. O2 utilization in the tissueRespiration-a process of gas exchangeRespiration-a process of gas exchangeExternal respiration O2 dependenceO2 dependenceLarge amount Large amount of Oof O2 2 consumption - consumption - 250ml/min (360L/day

3、)250ml/min (360L/day)Small amount Small amount of Oof O2 2 storage - storage - 1.5L (sustain life only six minutes)1.5L (sustain life only six minutes)Continuous hypoxia Continuous hypoxia 6 min-life-threatening6 min-life-threatening POPO2 2 (partial pressure of oxygen) (partial pressure of oxygen)

4、血氧分压血氧分压 Oxygen tension Oxygen tension 血氧张力血氧张力 the tension produced by oxygen molecules physically the tension produced by oxygen molecules physically dissolved in the blooddissolved in the blood Arterial (PaOArterial (PaO2 2): ): 100 mmHg (13.3kPa)100 mmHg (13.3kPa)， 取决于吸入气体的取决于吸入气体的氧分压和外呼吸功能氧分压和外

5、呼吸功能 Venous (PvOVenous (PvO2 2): ): 40 mmHg (5.33kPa) 40 mmHg (5.33kPa) ，取决于组织摄氧和，取决于组织摄氧和用氧的能力用氧的能力 Influence factors (IFs):Influence factors (IFs): Pressure of OPressure of O2 2 in the air in the air （空气氧分压）（空气氧分压） External respiratory function External respiratory function （外呼吸功能）（外呼吸功能） Shunt of

6、 blood Shunt of blood ( (血液分流血液分流) )Measurements of OMeasurements of O2 2 (1) (1) COCO2max 2max (oxygen binding capacity)(oxygen binding capacity)，最大血氧容量最大血氧容量 Maximal Maximal amount of oxygen that can be potentially bound by amount of oxygen that can be potentially bound by the haemoglobin (Hb), th

7、e haemoglobin (Hb), reflecting the ability of Hb carrying O2. reflecting the ability of Hb carrying O2. Under ideal condition, the binding capacity is 1.34 ml/g HbUnder ideal condition, the binding capacity is 1.34 ml/g Hb COCO2max 2max 反映血液携氧能力的强弱反映血液携氧能力的强弱 IFs:IFs: Quantity of Hb Quantity of Hb (

8、 (血红蛋白的量血红蛋白的量) ) Quality of Hb or affinity of Hb Quality of Hb or affinity of Hb ( (血红蛋白的质与亲和力血红蛋白的质与亲和力) )Measurements of OMeasurements of O2 2 (2) (2)COCO2: 2: (oxygen content), (oxygen content), 实际血氧含量实际血氧含量 thethe actual actual O O2 2 content in the blood, including the content in the blood, in

9、cluding the oxygen bound to the Hb and Ooxygen bound to the Hb and O2 2 dissolved in the dissolved in the blood.blood. Arterial COArterial CO2 2 (CaO (CaO2 2): 19 ml/dl): 19 ml/dl Venous COVenous CO2 2 (CvO (CvO2 2): 14 ml/dl): 14 ml/dl Differences of CODifferences of CO2 2 between arterial and veno

10、us between arterial and venous (Da-vCO(Da-vCO2 2): ): 动动- -静脉血氧含量差：静脉血氧含量差：5 ml/dl5 ml/dl IFs:IFs: PaOPaO2 2 COCO2 2 max-Hb quantity and quality max-Hb quantity and qualityMeasurements of OMeasurements of O2 2 (3) (3)SOSO2 2 (oxygen saturation) (oxygen saturation)， 血氧饱和度血氧饱和度 the percentage of oxyge

11、n-bound form (oxyhemoglobin) the percentage of oxygen-bound form (oxyhemoglobin) in total Hb.in total Hb. SOSO2 2=(=(血氧含量血氧含量- -溶解氧量溶解氧量) )、血氧容量、血氧容量X100%X100% Arterial (SaO2): 97-99%Arterial (SaO2): 97-99% Venous (SvO2): 75%Venous (SvO2): 75% IFs:IFs: POPO2 2 pH, temperaturepH, temperature CO2, DPG

12、CO2, DPGMeasurements of OMeasurements of O2 2 (4) (4) A curve reflecting the relationship between the POA curve reflecting the relationship between the PO2 2 and SOand SO2 2 S (sigmoid) shapeS (sigmoid) shape SOSO2 2 , SDC left shift , SDC left shift Hb affinityHb affinity SOSO2 2 , SDC right shift

13、, SDC right shift Hb affinityHb affinityO O2 2 saturation dissociation curve (SDC) saturation dissociation curve (SDC)Right shiftLeft shift P50: the POP50: the PO2 2 50% 50% SOSO2 2Reflecting the flexibility of Reflecting the flexibility of HbHb carrying carrying O2O2 SDC right shift , P50SDC right

14、shift , P50 SDC left SDC left shift, shift, P50P50 P50-a value indicating the flexibility of HbP50-a value indicating the flexibility of HbHypoxiaHypoxiaDefintion:Defintion:A pathological process in which A pathological process in which O O2 2 supply to tissues is supply to tissues is inadequate to

15、meet the demand of cells, or utilization of Oinadequate to meet the demand of cells, or utilization of O2 2 is is insufficient in cells despite adequate Oinsufficient in cells despite adequate O2 2 supply supply, leading to , leading to changes in changes in functions, metabolisms functions, metabol

16、isms and and structuresstructures of cells of cells and tissues in the body.and tissues in the body.Inadequate supply of O2 (氧供不足氧供不足)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 tissueClassification of hypoxia1. Hypoto

17、nic hypoxia2. Hemic hypoxia3. Circulatory hypoxia4. HistogenoushypoxiaThe most common type of hypoxiaThe most common type of hypoxia CausesCauses: : O2 O2 supplysupply Tibetan Plateau, mineral wellsTibetan Plateau, mineral wells Dysfunction in external Dysfunction in external respiration, respiratio

18、n, a.k.aa.k.a respiratory hypoxiarespiratory hypoxia Bronchial obstructionBronchial obstruction Respiratory muscle paralysisRespiratory muscle paralysis Venous-to-arterial Venous-to-arterial shuntsshunts Congenital cardiac defectsCongenital cardiac defectsHypotonic/hypoxic hypoxia(Hypotonic/hypoxic

19、hypoxia(低张性缺氧低张性缺氧) )Features:minor: PaO2 ; CO2 NSevere:PaO2 ; CO2max N, CaO2 ; SaO2 D(a-v)O2 or NCentral cyanosis (紫绀)Respiratory compensation Hypotonic/hypoxic hypoxiaHypotonic/hypoxic hypoxiaCyanosis (发绀或紫绀) Deoxyhemoglobin 5g/dlDeoxyhemoglobin 5g/dl (central cyanosis)(central cyanosis) Patients

20、with hypoxia can show cyanosis, but Patients with hypoxia can show cyanosis, but cynosis does not mean hypoxia.cynosis does not mean hypoxia. Patients with severe anemia (Patients with severe anemia (贫血贫血) )， with with total amount of hemoglobin 5g/dl, will not total amount of hemoglobin 1.5g/dl, 皮肤

21、，粘膜可出现青紫，皮肤，粘膜可出现青紫，为为肠源性肠源性紫绀紫绀。Features:Features:Normal PaONormal PaO2 2COCO2 2 max max and CaOand CaO2 2 O2 delivery to O2 delivery to tissue tissue COCO2 2 max normal but affinity max normal but affinity O2 O2 release to tissue release to tissue Hemic/isotonic hypoxiaHemic/isotonic hypoxia Inade

22、quate blood flow resulting in insufficient Inadequate blood flow resulting in insufficient oxygenation of the tissueoxygenation of the tissue Causes:Causes: GeneralGeneral circulatory dysfunction-shock, circulatory dysfunction-shock, heart failureheart failure Local Local circulatory dysfunction-ste

23、nosis, circulatory dysfunction-stenosis, occlusion, thrombosisocclusion, thrombosis Mechanisms-tissue perfusion Mechanisms-tissue perfusion ischemia hypoxia ischemia hypoxia （缺血性缺氧缺血性缺氧） congestive hypoxia congestive hypoxia （充血性缺氧充血性缺氧）Circulatory/hypokinetic hypoxiaCirculatory/hypokinetic hypoxia（

24、循环性缺氧）（循环性缺氧） Features: a. PaO2: N PvO2 b. CaO2: N CvO2 c. CO2max: N d. SaO2: N e. (Da-vCO(Da-vCO2 2) ) f. Peripheral cyanosis (外周性紫绀外周性紫绀) g. Respiratory compensationCirculatory/hypokinetic hypoxiaCirculatory/hypokinetic hypoxia（循环性缺氧）（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

25、， 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/Histogenous/dysoxidative hypoxia (dysoxidative hypoxia (组织性缺氧组织性缺氧) )Causes:Causes: Cell/tissue poisoningCell/tissue poisoning cyanide (cyanide (氰化物氰化物) poisoninghistotoxic ) poisoninghistotoxic hypoxiahypoxia A

26、rsenic poisoning (Arsenic poisoning (砒霜砒霜) ) Mitochondria injuryMitochondria injury radiation ; ROS radiation ; ROS Inadequate synthesis of biological oxidation Inadequate synthesis of biological oxidation coenzymecoenzyme deficiency of vitamin B deficiency of vitamin B2 2 or PPor PPMechanisms:Mecha

27、nisms:Aberrant Aberrant biological biological oxidation or oxidation or oxidative oxidative phosphorylation phosphorylation deficiency in deficiency in oxygen oxygen consumption consumption ATPATP . . Features: a. PaO2 = N, PvO2 b. CaO2 = N, CvO2 c. CO2max = N d. SaO2 = N e. (CaO2-CvO2) f. No cyanos

28、is g. No respiratory compensationFeatures of different types of hypoxia Type PaO2 SaO2 CO2 max CaO2 D(a-v)CO2Hypotonic hypoxia N or NHemic 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. Hypotonic hypoxia: PaOHypotonic hypoxia: PaO

29、2 2 Hemic hypoxia: Normal PaOHemic hypoxia: Normal PaO2 2, altered Hb , altered Hb quantity and quality, COquantity and quality, CO2 2max or max or Circulatory hypoxia: Normal PaOCirculatory hypoxia: Normal PaO2 2, Hb quantity , Hb quantity and quality, blood flow and quality, blood flow Histogenous

30、 hypoxia: normal OHistogenous hypoxia: normal O2 2 supply to the supply to the tissue, Otissue, O2 2 utilization utilization Features of different types of hypoxiaFeatures of different types of hypoxiaImpact of hypoxia on the bodySlight hypoxia: stimulationCompensatory responsesSevere hypoxia: impai

31、rmentdysfunction and failure of cells and tissuesAcute hypoxia: mainly damageChronic hypoxia: both damage and compensationRespiratory systemCirculatory systemHematologic systemCentral nervous system Tissues and cellsCompensatory reaction-hyperventilation (过度通气过度通气) PaO2 8Kpa or 60 mmHg chemoreceptor

32、srespiratory rate and depth hypoxic ventilation reaction (HVR).Consequences:respiratory surface, O2 diffusion, PaO2&SaO2More fresh air into the lung, 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

33、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 edemaRespiratory failureSevere hypoxia (PaO2 30 mmHg) inhibition of respiratory center slow and periodic or irregular breathing stop of breathing.Circulatory systemC

34、irculatory system Compensatory responsesCompensatory responses Cardiac output : tachycardia （心动过速） arrhythmia myocardial contractility Pulmonary vasoconstriction pulmonary arterial hypertension right heart failure Redistribution of blood ensure enough blood to heart and brain Capillary hyperplasiaIn

35、jury manifestationInjury manifestation Pulmonary hypertension Decreased diastolic and systolic myocardial function Arrhythmia Decrease in Venous blood return to the heart Hemic systemHemic systemCompensatory responsesCompensatory responses Rightward shift of oxyhemoglobin dissociation curve Increase

36、 of red blood cell and erythropoietin(EPO)Injury manifestationInjury manifestation Blood viscosity Brain is highly sensitive to hypoxia. Blood redistribution to the brainPaO28 mmHg， mental disorder Cerebral edemaCentral nervous system CellCellCompensation: Compensation: increased ability to use Oincreased ability to use O2 2 anaerobic glycolysis anaerobic glycolysis increase of myoglobinincrease of myoglobinInjur