呼吸科呼吸系统课件3.ppt

1、2023-1-42023-1-41 15.3.Gas transport5.3.Gas transportlOxygen is transported by the blood in both physically dissolved and hemoglobin-bond forms.lCarbon monoxide binds the same site on hemoglobin as oxygen does and is dangerous to life.lCarbon dioxide(CO2)is transported in three forms:physically diss

2、olved,bicarbonate,and carbaminohemoglobin2023-1-42023-1-42 2Oxygen Transport in the Blood2023-1-42023-1-43 3Hemoglobin(Hb)Each Hb molecule consists of four globular protein(globin,珠蛋白)subunits.Each subunit is composed of a protein chain tightly associated with a non-protein heme（血红素）group.Oxygen bin

3、ds to iron(Fe2+)on heme.2023-1-42023-1-44 4Two Forms of Oxygen Exist in the Two Forms of Oxygen Exist in the BloodBloodPhysically dissolved:2%Dissolved O2(ml/dL)=0.003(ml/dL/mmHg)X Pa O2(mmHg)Combined with Hb:98%Both physically dissolved and chemically bond are important.Oxyhemoglobin(HbO2):Hemoglob

4、in binds to oxygen.Deoxyhemoglobin (Hb):Hemoglobin that does not bind with oxygen.2023-1-42023-1-45 5Oxygen Binds to HemoglobinOxygen Binds to HemoglobinThe binding of oxygen to hemoglobin is reversible and very quick.The reaction of this biding is oxygenation but not oxidation(ferrous remains as fe

5、rrous).Each hemoglobin molecule can bind four oxygen molecules.Each gram of hemoglobin can bind up 1.341.39 ml of O2(depending on methemoglobin levels).2023-1-42023-1-46 6Positive CooperativityPositive CooperativityChanges in the affinity of hemoglobin as each successive O2 molecule binds to a heme

6、site.Binding of the first O2 molecule increases the affinity for the second O2 molecule,and so forth.The affinity for the forth O2 molecule is the highest.This change in affinity facilitates the loading of O2 in the lungs and the unloading of the O2 at the tissues.2023-1-42023-1-47 7Quantitative Des

7、cription of OQuantitative Description of O2 2 Binding Binding to Hbto HbOxygen capacity is the maximum of oxygen that hemoglobin can carry per 100 ml blood .Hb-bound oxygen content is the amount of oxygen actually carried by hemoglobin per100 ml blood.Oxygen saturation(SO2)is the percentage saturati

8、on of hemoglobin with oxygen that is calculated from the ratio of oxygen content over capacity.The relationship between and PO2 and SO2(or oxygen content)is oxyhemoglobin equilibrium curve(oxygen dissociation curve).2023-1-42023-1-48 8Oxygen Dissociation CurveOxygen Dissociation Curve2023-1-42023-1-

9、49 9Analysis of Oxygen Dissociation Analysis of Oxygen Dissociation Curve Curve When PaO2 is increased from 60 and 100 mmHg,SaO2 rises only by 7%.The clinical significance of the flat portion of oxygen dissociation curve is that a drop PO2 from 100 to 60 mmHg still results in hemoglobin saturation o

10、f 90%.Rising PaO2 above 100 mmHg barely affects oxygen content.In the steep portion of this curve,blood oxygen content and thus oxygen delivery to tissues are compromised upon PO2 falls below 60 mmHg.The significance of this portion of the curve is that a large amount of O2 is released from hemoglob

11、in with a small change in PO2.2023-1-42023-1-41010Changes in Blood Chemistry Alter Changes in Blood Chemistry Alter Hemoglobins Affinity for OHemoglobins Affinity for O2 2To rememberJust think that an exercising muscle is hot and acidic and produces large amount of carbon dioxide,all of which favor

12、the unloading of more oxygen to the metabolic needs of musclesDPG=2,3-diphosphoglycerate2023-1-42023-1-41111Bohr Effect Bohr Effect lBohr effect(after the Danish physiologist,Christin Bohr)refers to the effect of CO2 on the affinity of hemoglobin on oxygen.lIncreased CO2 shifts the oxyhemoglobin dis

13、sociation curve to the right,promoting oxygen release.lBohr effect is caused in part by the change in pH that occurs as CO2 increases.2023-1-42023-1-41212P P5050 Indicates the Binding Activity of Indicates the Binding Activity of Hemoglobin for OHemoglobin for O2 2lThe PO2 value at which 50%of hemog

14、lobin is saturated.lThe normal range is between 26 and 28 mmHg in arterial blood.lHigh P50 allows more O2 to be released.2023-1-42023-1-41313Carbon Monoxide Poisoning2023-1-42023-1-41414Properties of Carbon DioxideProperties of Carbon DioxidelCO is an odorless,colorless,and non-irritating gas;it is

15、virtually undetectablelCO is produced by incomplete combustionlWith enough O2,CO2 is generatedlWith less O2,CO is generated2023-1-42023-1-41515Carbon Monoxide Binds to the Site Carbon Monoxide Binds to the Site of Hb as Oxygen Doesof Hb as Oxygen DoeslIt binds to Hb at the same site as oxygen does,f

16、orming carboxyhemoglobin(HgbCO)and preventing O2 binding.lThe binding affinity for CO is 200-250 times as that for oxygen.2023-1-42023-1-41616Carbon Monoxide-Hemoglobin Dissociation Carbon Monoxide-Hemoglobin Dissociation CurveCurve2023-1-42023-1-41717Carbon Monoxide Reduces OCarbon Monoxide Reduces

17、 O2 2 Content Content2023-1-4172023-1-42023-1-41818Higher Concentration of Higher Concentration of Carboxyhemoglobin in Cigarette Smokers Carboxyhemoglobin in Cigarette Smokers In healthy individuals,carboxyhemoglobin occupies 12%of the Hb binding sitesIn people who smoke cigarettes,occupation of Hb

18、 binding sites can be increased up to 10%Stop smoking2023-1-42023-1-41919No Hyperventilation Response to Carbon No Hyperventilation Response to Carbon Monoxide PoisoningMonoxide PoisoningBecause arterial PO2 is normal,no feedback mechanism to warn that the oxygen content is low,so people with CO poi

19、soning will die peacefully 2023-1-42023-1-42020Treatments of Carbon Monoxide Treatments of Carbon Monoxide Poisoning Poisoning lThe appropriate treatment is the administration of pure oxygenlHigh CO2(5%)is helpful in stimulating respiration and consequently promoting the removal of CO from the blood

20、 2023-1-42023-1-42121Carbon Dioxide Transport2023-1-42023-1-42222The Source and Forms of Carbon The Source and Forms of Carbon DioxideDioxide2023-1-42023-1-42323Carbon Dioxide TransportCarbon Dioxide TransportCarbon dioxide is carried in the blood in three distinct forms:Physically dissolved in the

21、plasma(10%)As bicarbonate ions in the plasma and in the red cells(60%)As carbamino proteins(30%)2023-1-42023-1-42424Formation of Bicarbonate and Formation of Bicarbonate and Bicarbonate IonsBicarbonate IonsHCO3-moves out of RBC in exchange for chlorideChloride shift2023-1-42023-1-42525Carbaminohemog

22、lobin FormationCarbaminohemoglobin FormationlCarbon dioxide molecule reversibly attaches to an amino portion of hemoglobin to form carbaminohemoglobin（氨基甲酰血红蛋白）CO2 +HbHbCO22023-1-42023-1-42626COCO2 2 Dissociation Curve and the Dissociation Curve and the Haldane EffectHaldane Effect2023-1-42023-1-427

23、27The Relationship among OThe Relationship among O2 2,CO,CO2 2 and and H H+Bohr Effect The effect of PCO2 and H+on the affinity of hemoglobin on oxygen(or the oxygen-hemoglobin equilibrium curve).Haldane EffectFor any given PCO2,the blood will hold more CO2 when the PO2 is being reduced.2023-1-42023

24、-1-42828The Haldane EffectThe Haldane EffectlFor any given PCO2,the blood will hold more CO2 when the PO2 is being diminished.lThe effect is reversed in the lung when O2 is transported from the alveoli to the red blood cells.2023-1-42023-1-42929Summaries on Gas Exchange and Gas Summaries on Gas Exch

25、ange and Gas TransportTransportThe uptake of oxygen is determined by the diffusion properties of the alveolar-capillary membrane,the oxygen partial pressure gradient,and pulmonary capillary blood flow.Oxygen is transferred by the blood in two forms:dissolved and oxyhemoglobin.Oxygen dissociation cur

26、ve is the functional relationship between oxygen partial pressure and the percentage of hemoglobin saturated with oxygen.P50 is a measure of Hb affinity to bind with oxygen.Hb affinity is inversely related to P50.Changes in blood chemistry(pH,PaCO2,and temperature)and 2.3,DPG alter the oxygen dissoc

27、iation curve.2023-1-42023-1-43030Summaries on Gas Exchange and Gas Summaries on Gas Exchange and Gas Transport-ContinuedTransport-ContinuedlAs a product of non-complete combustion,CO is dangerous to life.l It binds to Hb in a competitive manner.lThe binding affinity for Hb is 250 times higher than t

28、hat of oxygens.lPaO2 is normal,so there is lack of feedback mechanism to indicate that oxygen content is low.lThe appropriate treatment is the administration of high concentration of oxygen;high CO2 may be helpful in the case of spontaneous breathing is still existed.2023-1-42023-1-43131Summary on O

29、xygen TransportSummary on Oxygen TransportlOxygen is transported by the blood in two forms:oxyhemoglobin and physically dissolved.lThe relationship between oxygen partial pressure and the saturation of hemoglobin is the oxygen dissociation curve.lChanges in blood chemistry(pH,PaCO2,temperature and 2

30、.3-DPG)alter oxyhemoglobin equilibrium curve.lP50 is a measure of Hb affinity to bind oxygen.When Hb affinity increases,the P50 changes in the opposite direction.2023-1-42023-1-43232Summary on Carbon MonoxideSummary on Carbon MonoxidelAs a product of non-complete burn,CO is odorless,colorless,and no

31、n-irritating gas;it is virtually undetectable.lIt binds to Hb at the same site as oxygen does.lThe binding affinity for Hb is 210 times as that of oxygens.lPaO2 is normal,so there is lack of feedback mechanism to indicate that oxygen content is low.lThe appropriate treatment is the administration of

32、 high concentration of oxygen;high CO2 may be helpful in the case of spontaneous breathing is still existed.2023-1-42023-1-43333Summary on Gas Transport-Carbon Summary on Gas Transport-Carbon DioxideDioxidelCarbon dioxide is transported in three distinct forms:lDissolved(10%)lBicarbonate in the plasma and in the red cells(60%)lHemoglobin(carbamino proteins,30%)