![]() ![]() On one side there is "wasted air" and on the other side there is "wasted blood." The total amount of wasted air constitutes physiological dead space and the total amount of wasted blood ( venous admixture) constitutes physiological shunt. "blood." The plumbing on both sides of the alveolar-capillary membrane is imperfect. Mixed venous / / blood / I PO2 = 40 mm Hg Pco2 = 46 mm HgĮnd-pulmonary capillary blood Po2 = 102 mm Hg PCO2 = 40 mm Hg ![]() Oxford: Butterworth-Heinemann, 2000.)Įffect of regional differences of ventilationperfusion ratios on blood gases in the apex and base of the lungs. ![]() The optimal Va/Q ratio is 0.8 in healthy lungs. The ventilation-perfusion ratio is shown on the x-axis, plotted on a logarithmic scale. The y-axis represents flow (either blood flow or airflow) in L/min. Profiles for alveolar ventilation and blood 'flow in healthy adults. On one side of the alveolar-capillary membrane there is "wasted air" (i.e., physiological dead space), and on the other side there is "wasted blood" (Fig. Uworld says this is v/q mismatch but that gets me confused cause why wouldn't a vent defect give v/q mismatch.Matching of the lung's airflow and blood flow is not perfect. That's why you will see a drop in PaO2 in PE(minor). So this one is tougher but: Let's assume you have a well ventilated alveoli, when there is poor oxygen content, vasculature will constrict and redistribute this blood to other alveolar however it will overwhelm the capacity of extracting oxygen into blood - so adding oxygen will help. Dead space/physiologic dead space/V/Q mismatch to inifinty.I remember total pulm shunt as if pulm art partial pressure = pulm vein partial pressure, shunted, basically just bypassed lungs. These alveolar are already extracting maximum oxygen, adding more would not help. Lets assume this kid have some alveoli that are working. pulm shunting - ventilation defect V/Q 0, perfusion intact.So this is my understanding of the topic and I might be wrong so please correct me if thats the case: ![]()
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