Oxygen Dissociation Curve

Oxy-hemoglobin dissociation curve : Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in PO2 Variant: Changes in O2 content with changes in PO2

Oxy-hemoglobin dissociation curve : Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in PO2 Variant: Changes in O2 content with changes in PO2 Dynamics

Slide 3 : Oxygen Transport Bohr Effect

Oxy-hemoglobin dissociation curve : Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in PO2 Variant: Changes in O2 content with changes in PO2 Dynamics Changes in position affect the tendency to load or unload oxygen: Bohr effect

Volume rate transfer(oxygen) : Volume rate transfer(oxygen) Oxygen Transport Lung 0.5-1.0 microns Skeletal Muscle 80 microns Brain 40 microns distance (L) can usually be decreased by recruitment Myocardium 12 microns (approximately one capillary per muscle cell)

At The Lung: : 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

Slide 7 : Transit Time (msec)

Slide 8 : Transit Time (msec) How about if transit time is decreased???

Slide 9 : 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)

Slide 10 : PO2 0 50 100 Oxygen Transport

Slide 11 : Oxygen Transport Adequate Critical Inadequate

Slide 12 : PO2 40 Oxygen Transport

Slide 13 : PO2 0 Oxygen Transport

Slide 15 : Oxygen Transport PO2 10 No Bohr effect Bohr effect

Oxy-hemoglobin dissociation curve : Oxy-hemoglobin dissociation curve Interpretation Standard: Reflects changes in Hb saturation with changes in PO2 Variant: Changes in O2 content with changes in PO2 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

Slide 17 : Oxygen Transport

Hypoxia: Inadequate tissue oxygenation : Hypoxia: Inadequate tissue oxygenation At the lung: hypoxic hypoxia At the blood: Anemia (reduced # RBCs or Hb) Carbon monoxide: left-shifted O2-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