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1 Author(s): Louis D Alecy, 2009 License: Unless otherwise noted, this material is made available under the terms of the Creative Commons Attribution Non-commercial Share Alike 3.0 License: We have reviewed this material in accordance with U.S. Copyright Law and have tried to maximize your ability to use, share, and adapt it. The citation key on the following slide provides information about how you may share and adapt this material. Copyright holders of content included in this material should contact open.michigan@umich.edu with any questions, corrections, or clarification regarding the use of content. For more information about how to cite these materials visit Any medical information in this material is intended to inform and educate and is not a tool for self-diagnosis or a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. Please speak to your physician if you have questions about your medical condition. Viewer discretion is advised: Some medical content is graphic and may not be suitable for all viewers.

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3 O 2 and CO 2 Transport M1 Cardiovascular/ Respiratory Sequence Louis D Alecy, Ph.D. Fall

4 Tuesday 11/18/08, 9:00 O 2 and CO 2 Transport 35 slides, 50 minutes 1. Describe the amount of oxygen dissolved and combined in blood. 2. Define oxygen delivery to a tissue. 3. Describe the characteristics of the oxygen-hb saturation curve. 4. Describe the shifts produced in the oxygen-hb saturation curve. 5. Describe the effects of anemia on oxygen content and PO State the three forms in which CO 2 is carried in the blood. 7. Describe the role of carbonic anhydrase in CO 2 transport. 8. Describe the chemical events associated with the uptake and release of CO Defines chloride shift. 4

5 Liquid blood Alveolar gas Source Undetermined O 2 content of blood = Dissolved + Hb bound O 2 5

6 How much gas is dissolved? A gas dissolves in a liquid in direct proportion to its partial pressure and solubility. Henry s Law 6

7 Henry s Law for O 2 The content of dissolved oxygen is equal to the product of the oxygen solubility coefficient and oxygen partial pressure. CdO = a O2 P O 2 Linear straight line Relationship like y = mx. = CdO2 content of dissolved O 2 ml/dl a 2 = solubility coefficient for O 2 in blood a O2 = ml/mm Hg/dL dl = 100 ml 7

8 Dissolved O 2 At PO 2 of 100 mmhg X you get 0.3 ml O 2 /dl dissolved oxygen in blood. With cardiac output of 5000 ml/min or 50 dl/min you would deliver (50 dl X 0.3 ml/dl) or 15 ml O 2 /min. BUT We consume 20 X that or 250 ml O 2 /min so dissolved just will not do it!! You need hemoglobin to bind and transport O 2. dl = 100 ml 8

9 Zephyris (wikipedia), Hemoglobin 9

10 Air Air Plasma Dissolved only D Alecy RBC Hb-O 2 bound + O 2 dissolved Not all Hb has O 2 10

11 How much O 2 is in blood? Concentration = Content ml/dl = ml/100ml = Vol% (ml of O 2 in 100 ml blood) i.e. arterial blood has 20 Vol% O 2 Content %Hb Saturation % Hb Saturation = O 2 bound to Hb X 100% O 2 capacity of Hb 11

12 O 2 content (with flow) determines O 2 delivery. Thus O 2 content is more important to O 2 delivery than is O 2 saturation. O 2 Content %Hb Saturation So why do we talk about O 2 saturation? O 2 saturation is relatively easier to measure and O 2 content is much more difficult to measure. We need to understand the differences!!!! 12

13 Hb Saturation Curve Normal Arterial Blood ~ 27 mmhg Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 13

14 % Hb Sat Or Sat Most O 2 combined. Linear straight line relationship. O 2 Content (ml / 100mL) Source Undetermined 14

15 O 2 Content (ml / 100mL) Different amounts of Hb but all 100% saturated! H b O 2 Saturation (%) Hb=10 Hb=15 Hb=20 Normal blood Hb = 15 gm/dl Source Undetermined 15

16 DO 2 (cc/m 2 /min) Anemia or Blood loss CI (L/m 2 /min) Bartlett, Critical Care Physiology 16

17 i.e. ANEMIA Decreased Hb concentration so that % saturation can be normal (97-100%) but O 2 content is decreased. 1. Decreased number of RBC 2. Decreased Hb content per RBC Normal blood Hb = 15 gm/dl 17

18 Denver? O 2 bars? O 2 Content (ml / 100mL) Source Undetermined Breathing 100% O 2. 18

19 Hemoglobin Bound Oxygen Content ml O 2 /dl C b O = S O 2 [ Hb ] Hb s 2 S O = % Hb saturation = O 2 bound to Hb X 100% O 2 capacity of Hb [ Hb ] = hemoglobin content gm/dl blood Hb s = saturated Hb O 2 content ml O 2 /gm Hb Hb s = 1.36 ml O 2 /gm Hb = O 2 capacity 19

20 Typical Arterial Blood Oxygen Content P O Dissolved O = 100 mm Hg S = 97% [ Hb ] = 15 gm/dl O 2 2 C d O 2 Bound O = a O 2 P O 2 = x 100 = 0.31 ml / dl C = S [ Hb ] Hb = 0.97 x 15 x 1.36 = ml / dl b O s O 2 2 Total Oxygen Content C d O 2 + C b O 2 = = 20.1 ml / dl 20

21 Bound Cb O ml / dl 20.1 Dissolved Cd O Total C O H b O 2 Saturation (%) % Source Undetermined 21

22 Content P ao2 C ao2 S O2 mm Hg ml / dl % Normal Hb 15 g/dl Breathing Room Air Anemia Hb 7.5 g/dl Breathing 100% O 2 Normal Hb 15 g/dl Anemia Hb 7.5 g/dl Thus breathing 100% O 2 does not fix reduced oxygen transport capacity due to anemia. 22

23 2X or 3X CO could compensate DO 2 (cc/m 2 /min) Anemia or Blood loss CI (L/m 2 /min) Bartlett, Critical Care Physiology 23

24 ph on O 2 Saturation of Hb Acid unloads O 2 from Hb (Bohr Effect) At any PO 2 less O 2 bound Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 24

25 CO 2 on O 2 Saturation of Hb CO 2 unloads O 2 from Hb (Bohr Effect) At any PO 2 less O 2 bound Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 25

26 Temperature on O 2 Saturation of Hb Temperature unloads O 2 from Hb At any PO 2 less O 2 bound Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 26

27 2,3-BPG on O 2 Saturation of Hb More 2,3-BPG unloads O 2 from Hb Lost in stored blood ~ canʼt unload O 2 Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 27

28 Venous blood on O 2 Saturation of Hb Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Venous blood unloads O 2 from Hb P 50 is PO 2 at 50% O2 saturation. 28

29 left shift (lungs) H + CO 2 temperature 2,3 BPG At any PO 2 more O 2 bound. right shift (tissues) Source Undetermined At any PO 2 less O 2 bound. 29

30 O 2 is unloaded in tissues O 2 HbO 2 D Alecy tissue metabolism right shift + H Temperature CO 2 30

31 In tissues CO 2 is stored in blood (for transport). CO 2 CO 2 CO 2 + H 2 O H 2 CO 3 C.A. = carbonic anhydrase chloride Shifts in Cl - HCO H + HbO 2 Bohr shift Buffer Action. O 2 O 2 O 2 + HHb tissue ISF plasma RBC Source Undetermined In tissues O 2 is unloaded from blood. 31

In lungs CO 2 is unloaded from blood. CO 2 CO 2 CO 2 + H 2 O chloride Shift out HCO 3 - H 2 CO 3 HCO 3 - + H + Cl - C.A.

32 In lungs CO 2 is unloaded from blood. CO 2 CO 2 CO 2 + H 2 O chloride Shift out HCO 3 - H 2 CO 3 HCO H + Cl - C.A. = carbonic anhydrase HbO 2 Haldane shift O 2 O 2 O 2 + HHb alveolus plasma RBC Source Undetermined In lungs O 2 is stored in blood. 32

33 How is CO 2 Transported? CO 2 is about 20 x more soluble than O 2 But still only 5% (art.) to 10% (ven.) of transport is dissolved!! The content of dissolved gas (C dx ) is the product of the solubility coefficient (a x ) and the partial pressure of the gas (P x ). Cdx = a x P x Cdx = dissolved gas content ml/dl a O2 = ml / mm Hg /dl = 0.06 ml / mm Hg /dl a CO2 33

34 Some Most Carbonic Anhydrase H + + Hb-NHCOO - = Hb + CO 2 + H 2 O = H + + HCO3 - Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 34

35 Reduced (de-ox)hb binds more CO 2 than HbO 2 Source Undetermined 35

36 Source Undetermined 36

37 Reduced (de-ox)hb binds more CO 2 than HbO 2, venous blood can carry more CO 2 then arterial blood. Venous Venous blood Arterial blood Arterial Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. 37

38 left shift (lungs) H + CO 2 temperature 2,3 BPG At any PO 2 more O 2 bound. right shift (tissues) Source Undetermined At any PO 2 less O 2 bound. 38

39 Slide 5: Source Undetermined Slide 9: GFDL, Zephyris (wikipedia), Slide 10: D Alecy Slide 13: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 14: Source Undetermined Slide 15: Source Undetermined Slide 16: Bartlett, Critical Care Physiology Slide 18: Source Undetermined Slide 21: Source Undetermined Slide 23: Bartlett, Critical Care Physiology Slide 24: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 25: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 26: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 27: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 28: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 29: Source Undetermined Slide 30: D Alecy Slide 31: Source Undetermined Slide 32: Source Undetermined Slide 34: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 35: Source Undetermined Slide 36: Source Undetermined Slide 37: Levitzky. Pulmonary Physiology. McGraw-Hill, th ed. Slide 38: Source Undetermined Additional Source Information for more information see:

For more information about how to cite these materials visit

For more information about how to cite these materials visit Author(s): Louis D Alecy, 2009 License: Unless otherwise noted, this material is made available under the terms of the Creative Commons Attribution Non-commercial Share Alike 3.0 License: http://creativecommons.org/licenses/by-nc-sa/3.0/