The partial pressure of oxygen in the lung alveoli is a bitlower than in ambient air, being about 100 mm of mercury, or 0.13Atm (it is lower than the partial pressure in air mainly becauseoxygen is continually taken up by the alveolar capillaries andcarbon dioxide is continually released into thealveoli).  In cell-free blood plasma (or a salinesolution formulated to match key characteristics of blood plasma),which lacks red blood cells and therefore lacks hemoglobin, theconcentration of oxygen will equilibrate at 37° Cat about 0.3 ml O₂/100 ml plasma. For whole blood(with hemoglobin), however, the O₂concentration is around 20 ml O₂/100 ml whole blood.

By what factor does the presence of hemoglobin increase theoxygen content of blood?

B.  Given the above, imagine that youare an emergency room physician treating a patient who lost aquarter of his blood in an accident. A paramedic replaced this lostblood with saline solution to keep his blood pressure up. Thesaline solution contains no hemoglobin since it contains no redblood cells. The patient is short of breath and oxygen levels inhis blood are dangerously low. If for some reason you must choosebetween administering pure (100%) oxygen or giving a transfusion ofwhole blood to restore the red blood cell count, which would youexpect to be more helpful? Address this decision by answering thequestions below. Show your work and be as quantitatively explicitas possible.

1. Under normal conditions, what percentage of blood oxygencontent is accounted for by oxygen dissolved in the plasma and whatpercentage is bound to hemoglobin? By how much do these percentageschange after the patient has a quarter of his blood volume replacedwith saline solution?
2. a) By what percentage could total blood oxygen content beincreased by delivering pure (100%) oxygen instead of allowing thepatient to simply breathe ambient air? Assume that Henry’s Lawapplies.

b) One obviously can’t deliver oxygen at a concentrationhigher than 100%, but how else might the partial pressure of theoxygen being delivered be modified to increase the amount diffusinginto the blood?

1. By what percentage could blood oxygen content be increasedby transfusing whole blood to restore the red blood cell count?Relative to delivering pure oxygen, is this a more promising orless promising approach for restoring normal blood oxygen levels?Explain.