Arterial PO2 decreases with chronic lung disease because physiologic shunt decreases O2 extraction ratio - USMLE Forums
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Old 03-17-2011
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Lungs Arterial PO2 decreases with chronic lung disease because physiologic shunt decreases O2 extraction ratio

I'm not sure I understand this. In FA it says "Arterial PO2 decreases with chronic lung disease because physiologic shunt decreases O2 extraction ratio"

Can anyone explain this?
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Old 03-17-2011
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Arterial PO2 decreases with chronic lung disease because physiologic shunt decreases O2 extraction ratio-alveoli.gif
click image to enlarge

I think because there is a V/P mismatch; normal perfusion with less ventilation (from fluid, chronic inflammation, tissue destruction, or whatever). The "shunt" is the blood going from pulmonary artery to pulmonary vein without ever getting oxygenated.
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Old 03-17-2011
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That makes complete sense! Awesome pic. Thank you so much It is clear now.
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Old 03-27-2011
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Thumbs Up Awesome

@Mondoshawan

You are awesome
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