In a patient with severe anemia but normal lungs, the oxygen concentration of aerial blood will be reduced, and therefore, if the cardiac output and oxygen uptake are normal, the oxygen concentration of mixed venous blood will also be reduced. The other choices are incorrect because the aerial PO2 and O2 saturation will be normal if the patient has normal lungs, but of course the aerial oxygen concentration will be reduced, and the tissue PO2 will therefore be abnormally low. Note that a patient with severe anemia usually has some increase in cardiac output, but neveheless, the oxygen concentration of mixed venous blood will be low. As in all these questions, the one best answer is being sought, and this is clearly D. Normal Aerial Po2, |Mixed venous Po2, |2,3-DPG