氧供需平衡麻醉課件

1、氧供需平衡Balance of Oxygen Supply and Demand,四川大學(xué)華西醫(yī)院 麻醉科魏蔚,氧輸送 oxygen transport (O2T),肺通氣肺換氣氧在血液中的運(yùn)輸氧在組織中釋放,氧瀑布 O2 Cascade,氧從空氣進(jìn)入細(xì)胞的線粒體內(nèi)要經(jīng)歷一系列過程，包括：肺通氣、肺換氣、氧在血液中的運(yùn)輸及氧在組織的釋放四個步驟。也有學(xué)者把氧運(yùn)輸過程中，從空氣中氧分壓159mmHg 至細(xì)胞內(nèi)的3~4mmHg的

2、巨大落差形象地稱為氧瀑布。,空氣 ?上呼吸道,飽和蒸汽壓=47mmHgPiO2=(760-47)0.2094=149mmHg,? 肺泡,二氧化碳 - PACO2, 約等于 PaCO2.PAO2 = PIO2 – PaCO2/R.- R 為呼吸商.- R＝ 0.8.- PAO2 = 149 – (40/0.8) = 100mmHg,?動脈血,氧從肺泡進(jìn)入肺靜脈氧分壓通常下降 5 –10 mmHg. PAO2=95mmHg,?

3、毛細(xì)血管 ?靜脈血,,毛細(xì)血管和組織間液間的較大的氧分壓差（ 30 mmHg）使得氧氣迅速由血液向組織彌散。,Summary,The factors influence transport of oxygen,Cardiac output Blood oxygen content (CaO2)The affinity of hemoglobin for oxygen,血紅蛋白與氧的結(jié)合量,1g 血紅蛋白最多可結(jié)合1.34ml的氧氣。

4、 (1.39ml when the hemoglobin is chemically pure)如果 Hb=15g/100ml, 最大結(jié)合的氧量 =15*1.34=20.1ml/100ml,在組織內(nèi)釋放的氧量,動脈血: SaO2=97%, CaO2=19.4ml/100ml混合靜脈血: PvO2=40mmHg, SvO2=75% CvO2=14.4ml/100mlC(a-v

5、)O2=19.4-14.4=5ml/100ml,,攝氧率（utilization coefficient/oxygen extraction）,The percentage of the blood that gives up its oxygen as it passes through the tissue capillaries is called the utilization coefficient.-normal valu

6、e is about 25%.-during exercise, can increase to 75~85%.,Physiological supply dependency,The normal relationship is for a 4:1 ratio between DO2 and VO2. ↑ or ↓ in CO and DO2 do not affect oxygen consumption.,Pathologica

7、l supply dependency,Relationship between DO2 and VO2 seen in critically ill patients, when increases in CO or increases in oxygen delivery, result in parallel increases in VO2.,氧-血紅蛋白解離曲線,Effects on Oxygen-Hemoglobin Di

8、ssociation Curve,The causes of a left-shifted oxy-Hb curve(P50<27mmHg),,Alkalosis –the Bohr effectHypothermiaAbnormal and fetal HbCarboxyhemoglobin, MethemoglobinDecreased 2,3-diphosphoglycerate,The causes of a r

9、ight-shifted oxy-Hb curve (P50>27mmHg),Increased hydrogen ionsIncreased CO2Increased temperatureIncreased 2,3-diphosphoglycerate (DPG),氧供Oxygen delivery DO2,DO2 是每分鐘供給機(jī)體的氧量。 DO2=(0.0031×PaO2+1.34×Hb

10、15;SaO2)×CODO2=1.34×Hb×SaO2×CO如果CO=5L,Hb=15g，DO2=1.34×150×1×5=1005ml/L,氧耗Oxygen consumption (VO2),Oxygen consumption is the actual amount of oxygen consumed per minute. VO2=CO×(

11、CaO2-CvO2)(ml/min) 正常情況下， 200~250ml/min.,.,,氧需Oxygen demand,Oxygen demand is the actual amount of oxygen needed per minute.-is closely related to the oxygen consumption;-Under some conditions, demand may exceed consu

12、mption.,氧供需失衡時機(jī)體的代償機(jī)制,CO↑.血流再分布.細(xì)胞攝氧率↑.,Monitoring?,理想部位：線粒體難點：細(xì)胞內(nèi)的氧合狀況無法直接監(jiān)測思路：對氧輸送過程進(jìn)行監(jiān)測,測定Hct及Hb的方法,全血細(xì)胞分析儀-- Hct、Hb血氣分析儀– Hct、Hb血紅蛋白分光光度儀-- Hb離心機(jī)—Hct,SpO2 monitored by Pulse oximetry since 1980 SO2=O2Hb/(O2Hb

13、+HHb)(%),If R940/R660=1, SO2=85%,Transcutaneous SpO2 monitoring,Two types oximetry:,反射式脈搏氧飽和度探頭,,The esophageal probe (ESOX, ARISTO Medical, Chicago, IL),Blood gas tension measurement,Oxygen pressure (PO2) PO2 is to

14、measure directly from a blood sample, usually by using a Clark electrode.Carbon dioxide pressure (PCO2) PCO2 electrodes work by measuring the change in pH induced when blood equilibrates with a potassium chloride/so

15、dium bicarbonate solution.,Mixed venous blood oxygen saturation (SvO2),,SvO2 monitoring,,連續(xù)頸內(nèi)靜脈血氧飽和度監(jiān)測,經(jīng)氣管混合靜脈血氧飽和度監(jiān)測,術(shù)中常用的CO監(jiān)測方法,右心飄浮導(dǎo)管Picco(外周動脈) FloTrac 傳感器TEE,由動脈壓力波形計算CO,CO = HR * Sd(AP) *

16、χ,PiCCO,Using PiCCO typically 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 solutio

17、n for the thermodilution analysis.,術(shù)中TEE測量CO,M型法短軸縮短率： FAC=(EDA-ESA)/EDA ; 自動邊緣識別系統(tǒng)（ABD）二維Simpson法 SV=LVEDV-LVSDV 多譜勒法 SV=時間速度積分X橫截面積 三維法,Calculation of the "shunt fraction",Qt = total cardiac output Qs

18、 = shunted portion of cardiac output Qns = normal pulmonary end-capillary blood flow that is not shunted past abnormal alveoli Qt = Qs + Qns or Qns = Qt - Qs,Calculation of the "shunt fraction",Qt (CaO2) =

19、total oxygen delivered to the body (DO2) Qs (CvO2) = oxygen content of shunted blood Qns (CcO2) = oxygen content of end-capillary blood Total oxygen delivered equals the sum of oxygen in both shunted and non-shunted

20、 blood Qt (CaO2) = Qs (CvO2) + Qns (CcO2),Calculation of the "shunt fraction",Substituting (Qt - Qs) for QnsQt (CaO2) = Qs (CvO2) + (Qt - Qs)(CcO2) Qt (CaO2) = Qs (CvO2) + Qt (CcO2) - Qs (CcO2) Qs (CcO2 -

21、 CvO2) = Qt (CcO2 - CaO2) The intrapulmonary shunt equationQs/Qt = CcO2 - CaO2 /CcO2 - CvO2,氧供需平衡的監(jiān)測,SvO2 60%~80%Oxygen extraction ratio (O2ER) O2ER=(CaO2-CvO2)/CaO2Lactic acid 7.32,,Gastric tonometr

22、y determines intraluminal PCO2 which is 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 gastr

23、ic tonometry and the bicarbonate concentration in arterial blood.,Baigorri et al. Critical Care 1997 1:61   doi:10.1186/cc104,決定DO2與VO2的因素,DO2,VO2,Hb,SaO2,CO,,,,SvO2,Hb,CO,SaO2,,.,術(shù)中影響氧供的因素,,,,DO2,CO/Hb,100%,50%,25%

24、,缺氧,低氧血癥：PaO2<60mmHg缺氧類型Hypotonic anoxiaAnemic anoxiaCirculatory anoxiaHistogenous anoxia,氧治療,Controlled oxygen treatment is used in those who need supplemental oxygen but not rely on their hypoxic drive to conti

25、nue breathing.-an increase in PaCO2 show they rely on hypoxic drive.,The rules of oxygen treatment,(1) Give oxygen as much as you can at first, and then reduce it, guided by blood gas measurements.(2) Oxygen treatment

26、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.,Oxygen therapy PaO2<60mmHg,Venturi mask. Th

27、e colour of the mask’s aperture reflects the FiO2 achieved (24%: blue; 28%: white; 35%: yellow;40%: red; 60%: green),Complications,CO2 ↑Absorption atelectasisOxygen intoxication,請討論,術(shù)中監(jiān)測氧供和氧耗的指標(biāo)？術(shù)中引起氧供下降的因素？根椐氧供與氧耗的相