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  #1  
Old 07-22-2012
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Question PaO2 level in CO-exposed patient

A 55-year-old woman with anemia is unknowingly exposed to carbon monoxide (CO) because of a faulty space heater in her home. She appears to be breathing normally, but says she does not feel well. Arterial and venous blood samples are taken. Laboratory studies would most likely show her arterial PaO2 as:

a) 25 mm Hg
b) 50 mm Hg
c) 70 mm Hg
d) 95 mm Hg
e) 120 mm Hg
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Old 07-22-2012
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methemoglobin on the disassociation curve

Carboxyhemoglobin Dissociation Curve!

O2 content is normal or decreases in anemia?

If anyone wants to get some help with this concept and anything related to it, I've discussed it with forum members many times above.

The links above show that I've struggled with this concept ever since I started step 1.
------------------------------------------------------------------------------

I believe the pO2 should be normal.

answer D, 95 mm HG
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  #3  
Old 07-22-2012
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D. normal PO2
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Old 07-22-2012
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D...normal value
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Matched!!!
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Old 07-22-2012
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Normal normal
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95mm hg...
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Old 07-23-2012
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Default correct answer :)

Correct answer is D) 95mm Hg

To understand why the patient’s PaO2 is still in the normal range (75–100 mm Hg), it is important to distinguish oxygen-carrying capacity from the oxygen content of blood. The oxygen-carrying capacity is the amount of oxygen the blood can carry when hemoglobin is maximally saturated, whereas the oxygen content of blood is the total amount of oxygen the blood actually contains. In this patient, oxygen content is decreased for two reasons: she has a true anemia due to a decreased amount of hemoglobin in her blood and she has a functional anemia due to CO binding to hemoglobin sites typically reserved for oxygen. However, neither of these problems has any effect on the PaO2, which depends solely on the amount of oxygen dissolved in plasma. PO2 is independent of the amount of hemoglobin and the number of sites available to bind oxygen.
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