1. Gas Exchange and Transport
Chapter 13
Gas Exchange and Transport
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

2. Concentration and Partial Pressure of Respired Gases
Partial pressure = Percentage of concentration of specific gas × Total pressure of a gas
Dalton’s law
Total pressure = Sum of partial pressure of all gases in a mixture
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

3. Ambient Air O2 = 20.93% = ~ 159 mm Hg PO2
CO2 = 0.03% = ~ 0.23 mm Hg PCO2
N2 = 79.04% = ~ 600 mm Hg PN2
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

4. Tracheal Air
Water vapor reduces the PO2 in the trachea about 10 mm Hg to 149 mm Hg.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

5. Alveolar Air Alveolar air is altered by entry of CO2.
Average alveolar PO2 = 103 mm Hg
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

6. Movement of Gas in Air and Fluids
Henry’s law
Gases diffuse from high pressure to low pressure.
Diffusion rate depends upon
Pressure differential
Solubility of the gas in the fluid
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

7. Pressure Differential
The difference in the pressure of specific gases from the capillary blood to the alveoli dictates the direction of diffusion.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

8. Solubility CO2 is about 25 times more soluble than O2.
CO2 and O2 are both more soluble than N2.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

9. Gas Exchange in Lungs & Tissues
Exchange of gases between lungs and blood and gas movement at the tissue level progress passively by diffusion, depending on their pressure gradients.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

10. Gas Exchange in the Lungs
PO2 in alveoli ~ 100 mm Hg
PO2 in pulmonary capillaries ~ 40 mm Hg
Result: O2 moves into pulmonary capillaries
PCO2 in pulmonary capillaries ~ 46 mm Hg
Average arterial blood gases equal
PO2 100 mm Hg
PCO2 40 mm Hg
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

11. Pulmonary Disease Gas transfer capacity may be impaired by
Thickening of membrane
Reduction in surface area
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

12. Gas Transfer in Tissues
Pressure gradients cause diffusion of O2 into and CO2 out of tissues.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

14. Transport of O2 in the Blood
Two mechanisms exist for O2 transport
Dissolved in plasma
Combined with hemoglobin
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

15. Oxygen in Physical Solution
For each 1 mm Hg increase, mL O2 dissolves into plasma.
This results in ~ 3 mL of O2/liter blood.
With 5 L total blood volume = 15 mL dissolved O2
Dissolved O2 establishes the PO2 of the blood.
Regulates breathing
Determines loading of hemoglobin
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

16. Oxygen Combined with Hemoglobin
Each of four iron atoms associated with hemoglobin combines with one O2 molecule.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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18. Oxygen-Carrying Capacity of Hb
Each gram of Hb combines with 1.34 mL O2.
With normal Hb levels, each dL of blood contains about 20 mL O2.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

19. Anemia Affects Oxygen Transport
Volume percent (vol%) refers to the milliliters of oxygen extracted from a 100-mL sample of whole blood.
Human blood carries O2 at 14 vol%.
Iron deficiency anemia reduces O2 carrying capacity considerably.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

20. PO2 and Hb Saturation
Oxyhemoglobin dissociation curve illustrates the saturation of Hb with oxygen at various PO2 values
Percent saturation = 12 vol% / 20 vol% × 100 = 60%
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

21. PO2 in the Lungs Hb ~ 98% saturated under normal conditions
Increased PO2 doesn’t increase saturation.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

22. PO2 in Tissues At rest PO2 = 40 mm Hg
Venous blood carries ~ 70% of the O2 content of arterial blood.
Venous blood carries 15 mL O2 per dL blood.
Tissues have extracted 5 mL O2 per dL blood.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

23. Arteriovenous O2 Difference
The a- O2 difference shows the amount of O2 extracted by tissues.
During exercise a- O2 difference increases up to 3 times the resting value.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

24. Bohr Effect Conditions creating the Bohr effect
Increased PCO2
Increased temperature
Increased 2,3-DPG
Decreased pH
Cause a shift to the right of the oxyhemoglobin dissociation curve
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McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

27. RBC 2,3-DPG 2,3-DPG is a byproduct of glycolysis/
RBCs contain no mitochondria.
Rely on glycolysis
2,3-DPG increases with intense exercise and may increase due to training.
Helps deliver O2 to tissues
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

28. Myoglobin, The Muscle’s O2 Store
Myoglobin is an iron-containing globular protein in skeletal and cardiac muscle.
Stores O2 intramuscularly
Myoglobin contains only 1 iron atom.
O2 is released at low PO2.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

29. CO2 Transport Three mechanisms Bound to Hb Dissolved in plasma
Plasma bicarbonate
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

30. CO2 in Physical Solution
~ 5% CO2 is transported as dissolved CO2.
The dissolved CO2 establishes the PCO2 of the blood.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

31. CO2 Transport as Bicarbonate
CO2 in solution combines with water to form carbonic acid.
Carbonic anhydrase
Zinc-containing enzyme within red blood cell
Carbonic acid ionizes into hydrogen ions and bicarbonate ions.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

32. CO2 Transport as Carbamino Compounds
CO2 reacts directly with amino acid mq to form carbamino compounds.
Haldane Effect: Hb interaction with O2 reduces its ability to combine with CO2.
This aids in releasing CO2 in the lungs.
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McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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