Chapter 5 Hypoxia P69,Department of Pathophysiology Molin Li,Questions,（1）How long will you live if there is no food, but plenty of water? （2）How long will you live if there is no food no water? （3）How long will you live if there is no oxygen?,Oxygen is vital to life.,O2,CaO2,Hb,O2,CaO2,供氧过程,利用氧,CvO2,CvO2,Blood,blood flow,PaO2,肺v.,主a.,肺a.,腔v.,Oxygen supply =CaO2 X tissue blood flow Oxygen consumption =Ca-vO2 X tissue blood flow,氧的获得和利用,Concept of hypoxia,Hypoxia refers to a deficiency of oxygen in either the delivery or the utilization at the tissue level, which can lead to changes in function，metabolism and even structure of the body. 指组织 供氧减少或用氧障碍，从而引起其代谢、功能以致形态结构发生异常变化的病理过程。,第一节,常用血氧指标及其意义,1. 血氧分压 (partial pressure of oxygen, PO2),Oxygen dissolved in plasma form an oxygen tension 物理溶解的 O2 产生的张力(氧张力),正常值,吸入气 PAO2,外呼吸功能,组织摄氧和用氧的能力,影响因素,指100ml血液中的血红蛋白，在氧分压为150mmHg 、二氧化碳分压为40mmHg、温度为38时，所能结合氧的最大毫升数，即100ml血液中血红蛋白（Hb）的最大带氧量 。,正常值,1g Hb可结合1.34ml O2 15g Hb 20 ml O2,取决于 Hb 的质与量 Hb的质: 与氧结合的能力 Hb的量: 每100ml血所含Hb的数量,2. Oxygen binding capacity, CO2 max（氧容量）,3. O2 content, CaO2（氧含量）,指100ml血液中实际含有的氧量(ml数)，包括物理溶解的和化学结合的氧量，但因正常时物理溶解的氧量很少(0.3ml/dl)，常可忽略不计。,正常值:,动脉血 19 ml/dl; 静脉血 14 ml/dl,取决于 氧分压与 氧容量,4. oxygen saturation, SaO2（氧饱和度）,正常值,动脉血 93-98%; 静脉血 70-75%,取决于 氧分压, 两者的关系可用氧解离曲线表示,( 血氧含量溶解的氧量),血氧容量,SaO2 (%) ,100%,CO2max,氧分压与氧饱和度的关系 氧解离曲线,氧 饱 和 度 %,氧分压 (mmHg),pH 2,3DPG CO2 T,pH 2,3DPG CO2 T,P50: 反映Hb与氧亲和力的指标。SO2为50%时的PO2。P50增大，Hb与氧的亲和力减小。,P50,表. 氧 解 离 曲 线 的 特 点,PO2 SO2(%) 线形 意义 部位 特点 上段 60100 9097.4 平坦 Hb与O2结合 肺 PO2变化 对SO2影响不大 中段 4060 7590 较陡 HbO2释放02 安静 PO2 100 40 组织 100ml血液释放 O25ml 下段 15 40 22 75 陡 Hb与O2解离 活动增 PO2略降 SO2 强组织 供给组织足够 的O2,Blood Oxygen is important index reflexing supply of O2 to tissue and tissues consumption of O2,PaO2 : partial pressure of blood oxygen CO2max :oxygen binding capacity CaO2 : oxygen content SaO2 : oxygen saturation D(CaO2-CvO2): the arterio-venous difference,capacity,第二节 缺氧的类型、原因和发病机制 （重点）,（一）低张性缺氧 (hypotonic hypoxia) （二）血液性缺氧 (hemic hypoxia) （三）循环性缺氧 (circulatory hypoxia) （四）组织性缺氧 (histogenous hypoxia),Classification of hypoxia (缺氧的类型),O2,CaO2,Hb,O2,CaO2,供氧过程,利用氧,低张性缺氧,血液性缺氧,循环性缺氧,组织性缺氧,CvO2,Blood血,肺v.,主a.,腔v.,肺a.,CvO2,PaO2,一、乏氧性缺氧（hypoxic hypoxia),概念： 以动脉血氧分压（PaO2）降低为基本特征的缺氧称为乏氧性缺氧，又称低张性缺氧（ Hypotonic Hypoxia ）。 hypotonic hypoxia refers to decreased PaO2, making CaO2 reduced and causing an inadequate supply of O2 to tissue . 由于动脉血氧分压降低， 使氧含量减少，组织供氧不足,Hypoxia =?= hypoxemia,Hypoxemia: PaO260mmHg,1. 原因与机制,(1)外环境氧分压过低 decreased PO2 in inspired air : 见于登上高山等、通气不良的矿井等,(2)外呼吸功能障碍external respiratory dysfunction: 见于肺通气功能障碍、肺换气功能障碍,(3)静脉血分流入动脉shunting of venous into arterial blood: 见于有右向左分流的心脏病,Altitude air pressure PairO2 PAO2 (m) (mmHg) (mmHg) (mmHg) Sea level 760 159 105 1000 680 140 90 2000 600 125 70 3000 530 110 62 5000 405 85 45 366 74 40 8000 270 56 30,外环境氧分压过低,left -toright shunt right-to-left shunt,Ventricular septal defect Ventricular septal defect with pulmonary artery constriction,ventricle,atrium,aorta,3. 血氧指标的变化,2 组织缺氧的机制,PaO2,毛细血管 PO2,PaO2 CaO2 SaO2 CO2max D(CaO2- CvO2 ) 4. 皮肤粘膜: 发绀,Concept of Cyanosis (发绀),Average deoxygenated Hb(HHb) in the blood capillary is increased by more than 5g/dl (gram/deciliter), which make the skin and mucosa such as lips, nailbeds appear bluish discoloration. 毛细血管中的脱氧Hb平均浓度超过5g/dl, 皮肤粘膜青紫色,The relationship between hypoxia and cyanosis,1.Cyanosis is an appearance of hypotonic and circulatory hypoxia 2.Severe anemia does not appear cyanosis 3.A person with polycythemia(红细胞增多症) or in cold environment may have cyanosis though hypoxia is absent at this time,二 血液性缺氧（hemic hypoxia）,概念：由于血红蛋白数量减少或性质改变，以致血液携带氧的能力降低或血红蛋白结合的氧不易释出而引起的缺氧称血液性缺氧（hemic hypoxia). hemic hypoxia refers to the altered quantity/ quality （the affinity for O2 ）of hemoglobin (Hb), resulting in tissue hypoxia. 血液性缺氧的特征性血氧变化是血氧容量降低。,1 血红蛋白（Hb）是由两对珠蛋白肽链和 4 个亚铁血红素构成。珠蛋白 4条肽链（、链）；亚铁血红素：原卟啉、铁。 2 特点 ：（1）正常情况下，99%Hb为还原Hb（HbA），1%为高铁Hb（HbF）。（2）只有Fe2+状态的Hb才能与氧结合，称为氧和血红蛋白。,原因与机制:,The decreased quanity of Hb:,The altered quality of Hb:,anemia,CO poisoning CO中毒,Methemoglobinemia 高铁血红蛋白血症,The hypoxic mechanisms of CO poisoning,The affinity of Hb for CO is much higher than its Affinity for O2, (Hb与CO的亲和力比O2高210倍) CO induce the HbO2 dissociation curve shifting to the left because CO inhibit glycolysis within RBC, which reduce the production of 2,3 DPG, therefore impaired ability to unload O2 in the tissue CO能抑制红细胞内糖酵解，使2,3 DPG减少， 氧解离曲线左移 .,The hypoxic mechanisms of Methemoglobinemia,Fe3+不能携氧,Fe2+-O2不能解离,HbFe3+OH,1. HbFe3+OH lose the ability of Hb carrying O2 because the Fe3+ in Hb combine with OH tightly. 2. HbFe3+OH make the HbO2 dissociation curve shif