In which of the following conditions would PaO₂ be normal but CaO₂ would be reduced?
I.Chronic anemia
II.CO poisoning
III.Methemoglobinemia
A) I, II and III
B) I only
C) I and III only
D) I and II only

Question

Quizplus · Accepted Answer

In chronic anemia, CO poisoning, and methemoglobinemia, the partial pressure of oxygen (PaO₂) in the blood can be normal because it measures the amount of oxygen gas dissolved in the blood, not the amount of oxygen bound to hemoglobin. However, the total oxygen content (CaO₂), which includes oxygen bound to hemoglobin, would be reduced in these conditions due to decreased hemoglobin availability (chronic anemia), inability of hemoglobin to bind oxygen (CO poisoning), or conversion of hemoglobin to a form that cannot bind oxygen effectively (methemoglobinemia).

In Which of the Following Conditions Would PaO₂ Be Normal