2. Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in P O 2 Variant: Changes in O2 content with changes in P O 2

3. Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in P O 2 Variant: Changes in O2 content with changes in P O 2 Dynamics

4. 100 80 60 40 20 0 406080100 %Saturation PO 2 (mmHg) P 50  Temp, CO 2, 2-3 DPG;  pH (favors unloading) Oxygen Transport P 50  Temp, CO 2, 2-3 DPG;  pH (favors loading) Bohr Effect

5. Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in P O 2 Variant: Changes in O2 content with changes in P O 2 Dynamics Changes in position affect the tendency to load or unload oxygen: Bohr effect

6. Volume rate transfer (oxygen) Oxygen Transport VO 2 = D * A * (P c O 2 - P t O 2 ) L2L2 Lung0.5-1.0 microns Skeletal Muscle80 microns Brain40 microns distance (L) can usually be decreased by recruitment Myocardium12 microns (approximately one capillary per muscle cell)

7. At The Lung: 70-80% of alveolar surface is covered by a single cell layer of red blood cells Maximal capacity is ~200 ml blood Normal blood volume in the capillaries is ~70 ml Alveolar-hemoglobin distance is 0.5 to 1.0 µm Capillaries cover several contiguous alveoli capillaries travel ~600-800 µm before joining a venule In a normal resting individual, it takes ~750 msec for an RBC to traverse a gas exchange section

8. Transit Time (msec) 0250500750 PO 2 (mmHg) 0 50 100 Alveolar PO 2 Normal Abormal Grossly abnormal 2 Blood PO

9. Transit Time (msec) 0250500750 PO 2 (mmHg) 0 50 100 Alveolar PO 2 Blood PO 2 How about if transit time is decreased???

10. Oxygen uptake by blood (at the lung) is normally considered perfusion-limited The amount of oxygen taken up by blood at the lungs is normally limited only by the rate of blood flow Oxygen uptake by tissue (from blood) is normally considered diffusion-limited The amount of oxygen taken up by tissue from the blood is normallly limited by diffusion characteristics (partial pressure gradient, distance)

11. PO 2 0 50 100 Oxygen Transport

12. Oxygen Transport 100 0 50 PO 2 Adequate R c Critical Anoxic Inadequate

13. PO 2 100 80 40 Oxygen Transport 60

14. PO 2 100 50 30 50 100 30 20 10 0 Lethal Corner Oxygen Transport

15. 2 Hb Saturation (%) 100 80 60 40 20 0 406080 100 P O (mmHg)

16. Oxygen Transport PO 2 100 70 40 70 100 50 10 0 PO 2 100 70 10 40 2 Hb Saturation (%) 100 80 60 40 20 0 406080 100 P O (mmHg) No Bohr effect Bohr effect

17. Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in P O 2 Variant: Changes in O2 content with changes in P O 2 Dynamics Changes in position affect the tendency to load or unload oxygen: Bohr effect Changes in shape usually reflect chemical alteration of the molecule Methemoglobin Thalessemias Carbon monoxide

18. Oxygen Transport SaO 2 = 97 SaO 2 = 62 (CO Hb=35%) O 2 Content (ml O 2 /dl blood) 0 20 16 12 8 4 PO 2 (mmHg) 20406080100

19. Hypoxia: Inadequate tissue oxygenation At the lung: hypoxic hypoxia At the blood: Anemia (reduced # RBCs or Hb) Carbon monoxide: left-shifted O 2 -Hb curve and decreased carrying capacity Hypoxemia due to hemoglobin mutation (thalassemia) Perfusion-related (stagnant hypoxia) Tissue level Metabolic disorders Poisons Cyanide: inhibits oxidative phosphorylation Dinitrophenol: uncouples oxidative phosphorylation Carbon monoxide (cytochrome binding): prevents electron transfer to oxygen