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Related Flashcards
Cards In This Set
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Distribution of ventilation in the lung
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Greater at the base than apex
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Distribution of perfusion in the lung
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Greater at the base than apex
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Ventilation and perfusion is greater at the base/apex of the lung
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BASE
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Which is more greatly affected by gravity - ventilation/perfusion?
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Perfusion- this is b/c blood is heavier than the air, so the difference in perfusion b/t the base and apex is greater than the difference in ventilation b/t the base and apex.
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When is gas exchange optimal?
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When ventilation and perfusion are going to the same places
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T/F. Ventilation and perfusion are always going to the same place.
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FALSE. Even in normal subjects, they are slightly mismatched. The effect on gas exchange depends on the extent to which they're mismatched. For example, if all of the ventilation went to the left lung and all of the perfusion went to the right lung, we could have normal alveolar ventilation and normal cardiac output but NO GAS EXCHANGE.
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Reminder: Henry's law
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Amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas and its solubility
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The amount of O2 that dissolves in the blood will be directly proportional to the partial pressure of O2 and its solubility in blood, and this amount will be in addition to __________
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The O2 that is already in the blood and chemically bound to Hb.
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What is the solubility of O2 at body temperature?
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0.003 ml/Torr/dL
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Normal amount of dissolved O2 in the blood
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0.3 mL O2 / dL of blood
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Describe the uptake of O2 by the blood.
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O2 is not just dissolved into blood. If this were the case, we wouldn't have enough O2 to supply the tissues. O2 is also bound to Hb in the blood in large amounts relative to the volume of the blood. Amount of O2 loaded onto Hb is directly (but not linearly) related to blood PO2 level until all of the binding sites for O2 on Hb are saturated. After all the Hb is completely saturated, further increases in PO2 will just increase the PO2 in the blood (i.e. dissolved O2).
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What is the shape of the Hb saturation vs. PO2 curve?
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Sigmoidal, S-shape
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Why is the shape of the Hb saturation vs. PO2 curve sigmoidal?
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At the beginning, increases in O2 bind to Hb at a slower rate. As more O2 binds to Hb, changes the conformation of Hb to have higher affinity for binding more O2. This accounts for the steep increase in the curve. As the Hb reaches full saturation, there are not as many binding sites available, so further increases in PO2 do not increase Hb saturation. This accounts for the top, flattened portion of the curve.
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Normal Hb concentration level
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15 gm/dL
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Each gram of Hb can hold ________ of O2 when fully saturated
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1.39 mL O2
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