1、肺通气肺通气肺换气肺换气氧在血液中的运输氧在血液中的运输氧在组织中释放氧在组织中释放 氧从空气进入细胞的线粒体内要经历一系氧从空气进入细胞的线粒体内要经历一系列过程，包括：肺通气、肺换气、氧在血液中列过程，包括：肺通气、肺换气、氧在血液中的运输及氧在组织的释放四个步骤。也有学者的运输及氧在组织的释放四个步骤。也有学者把氧运输过程中，从空气中氧分压把氧运输过程中，从空气中氧分压159mmHg 至细胞内的至细胞内的34mmHg的巨大落差形象地称为的巨大落差形象地称为氧瀑布。氧瀑布。饱和蒸汽压饱和蒸汽压=47mmHgPiO2=(760-47)0.2094=149mmHg v二氧化碳二氧化碳-PACO
2、2,约等于约等于 PaCO2.vPAO2=PIO2 PaCO2/R.-R 为呼吸商为呼吸商.-R 0.8.-PAO2=149 (40/0.8)=100mmHgw 氧从肺泡进入肺静脉氧分压通常下降氧从肺泡进入肺静脉氧分压通常下降 5 10 mmHg.PAO2=95mmHgw 毛细血管和组织间液间的较大的氧分压差毛细血管和组织间液间的较大的氧分压差（30 mmHg）使得氧气迅速由血液向组）使得氧气迅速由血液向组织弥散织弥散。w 1g 血红蛋白最多可结合血红蛋白最多可结合1.34ml的氧气。的氧气。(1.39ml when the hemoglobin is chemically pure)w 如果
3、如果 Hb=15g/100ml,最大结合的氧量最大结合的氧量=15*1.34=20.1ml/100mlw 动脉血动脉血:SaO2=97%,CaO2=19.4ml/100mlw 混合静脉血混合静脉血:PvO2=40mmHg,SvO2=75%CvO2=14.4ml/100mlw C(a-v)O2=19.4-14.4=5ml/100mlutilization coefficient/oxygen extraction）w The percentage of the blood that gives up its oxygen as it passes through the tissue capil
4、laries is called the utilization coefficient.-normal value is about 25%.-during exercise,can increase to 7585%.The normal relationship is for a 4:1 ratio between DO2 and VO2.or in CO and DO2 do not affect oxygen consumption.w Relationship between DO2 and VO2 seen in critically ill patients,when incr
5、eases in CO or increases in oxygen delivery,result in parallel increases in VO2.Alkalosis the Bohr effectHypothermiaAbnormal and fetal HbCarboxyhemoglobin,MethemoglobinDecreased 2,3-diphosphoglycerateIncreased hydrogen ionsIncreased CO2Increased temperatureIncreased 2,3-diphosphoglycerate(DPG)w DO2
6、是每分钟供给机体的氧量。是每分钟供给机体的氧量。w DO2=(0.0031PaO2+1.34HbSaO2)COw DO2=1.34HbSaO2CO如果如果CO=5L,Hb=15g，DO2=1.3415015=1005ml/L VO2=CO(CaO2-CvO2)(ml/min)正常情况下，正常情况下，200250ml/min.w CO.w 血流再分布血流再分布.w 细胞摄氧率细胞摄氧率.Monitoring?理想部位：线粒体难点：细胞内的氧合状况无法直接监测思路：对氧输送过程进行监测测定测定Hct及及Hb的方法的方法全血细胞分析仪全血细胞分析仪-Hct、Hb血气分析仪血气分析仪 Hct、Hb血红
7、蛋白分光光度仪血红蛋白分光光度仪-Hb离心机离心机HctSpO2 monitored by Pulse oximetry since 1980 SO2=O2Hb/(O2Hb+HHb)(%)If R940/R660=1,SO2=85%Two types oximetry:反射式脉搏氧饱和度探头反射式脉搏氧饱和度探头The esophageal probe(ESOX,ARISTO Medical,Chicago,IL)PO2 is to measure directly from a blood sample,usually by using a Clark electrode.PCO2 elec
8、trodes work by measuring the change in pH induced when blood equilibrates with a potassium chloride/sodium bicarbonate solution.连续颈内静脉血氧饱和度监测连续颈内静脉血氧饱和度监测经气管混合静脉血氧饱和度监测经气管混合静脉血氧饱和度监测术中常用的术中常用的CO监测方法监测方法w 右心飘浮导管w Piccow(外周动脉)FloTrac 传感器w TEE由动脉压力波形计算由动脉压力波形计算COCO =HR *Sd(AP)*PiCCOwUsing PiCCO typical
9、ly requires insertion of a thermodilution catheter in the femoral or axillary artery instead of a standard arterial line.Any available central venous catheter can be used to inject the solution for the thermodilution analysis.术中术中TEE测量测量COw M型法短轴缩短率：FAC=(EDA-ESA)/EDA;自动边缘识别系统（ABD）w 二维Simpson法 SV=LVE
10、DV-LVSDV w 多谱勒法 SV=时间速度积分X横截面积 w 三维法 Calculation of the shunt fractionw Qt=total cardiac output w Qs=shunted portion of cardiac output w Qns=normal pulmonary end-capillary blood flow that is not shunted past abnormal alveoli w Qt=Qs+Qns w or Qns=Qt-Qs Calculation of the shunt fractionw Qt(CaO2)=tota
11、l oxygen delivered to the body(DO2)w Qs(CvO2)=oxygen content of shunted blood w Qns(CcO2)=oxygen content of end-capillary blood Total oxygen delivered equals the sum of oxygen in both shunted and non-shunted blood w Qt(CaO2)=Qs(CvO2)+Qns(CcO2)Calculation of the shunt fractionSubstituting(Qt-Qs)for Q
12、nsw Qt(CaO2)=Qs(CvO2)+(Qt-Qs)(CcO2)w Qt(CaO2)=Qs(CvO2)+Qt(CcO2)-Qs(CcO2)w Qs(CcO2-CvO2)=Qt(CcO2-CaO2)The intrapulmonary shunt equationw Qs/Qt=CcO2-CaO2/CcO2-CvO2 w SvO2 60%80%w Oxygen extraction ratio(O2ER)O2ER=(CaO2-CvO2)/CaO2w Lactic acid 7.32wGastric tonometry determines intraluminal PCO2 which i
13、s assumed to be in equilibrium with PCO2 in the gastric mucosa.Intramucosal pH(pHim)can be calculated by the Henderson-Hasselbach equation using the PCO2 value determined by gastric tonometry and the bicarbonate concentration in arterial blood.oBaigorri et al.Critical Care 2019 1:61 doi:10.1186/cc10
14、4决定决定DO2与与VO2的因素的因素DO2VO2HbSaO2COSvO2HbCOSaO2.术中影响氧供的因素术中影响氧供的因素DO2CO/Hb100%50%25%缺氧缺氧w 低氧血症：PaO260mmHgw 缺氧类型Hypotonic anoxiaAnemic anoxiaCirculatory anoxiaHistogenous anoxia 氧治疗氧治疗wControlled oxygen treatment is used in those who need supplemental oxygen but not rely on their hypoxic drive to conti
15、nue breathing.-an increase in PaCO2 show they rely on hypoxic drive.(1)Give oxygen as much as you can at first,and then reduce it,guided by blood gas measurements.(2)Oxygen treatment will work only if the patient has a patent airway and is breathing.(3)Definitive treatment of hypoxia depends on the underlying cause.Giving oxygen is a holding measure.w CO2 w Absorption atelectasisw Oxygen intoxication请讨论请讨论w 术中监测氧供和氧耗的指标？术中监测氧供和氧耗的指标？w 术中引起氧供下降的因素？术中引起氧供下降的因素？w 根椐氧供与氧耗的相关知识，试推一下肺根椐氧供与氧耗的相关知识，试推一下肺内分流率的计算公式。内分流率的计算公式。
