In: Biology
The partial pressure of oxygen in the lung alveoli is a bit lower than in ambient air, being about 100 mm of mercury, or 0.13 Atm (it is lower than the partial pressure in air mainly because oxygen is continually taken up by the alveolar capillaries and carbon dioxide is continually released into the alveoli). In cell-free blood plasma (or a saline solution formulated to match key characteristics of blood plasma), which lacks red blood cells and therefore lacks hemoglobin, the concentration of oxygen will equilibrate at 37° C at about 0.3 ml O2/100 ml plasma. For whole blood (with hemoglobin), however, the O2 concentration is around 20 ml O2/100 ml whole blood.
By what factor does the presence of hemoglobin increase the oxygen content of blood?
B. Given the above, imagine that you are an emergency room physician treating a patient who lost a quarter of his blood in an accident. A paramedic replaced this lost blood with saline solution to keep his blood pressure up. The saline solution contains no hemoglobin since it contains no red blood cells. The patient is short of breath and oxygen levels in his blood are dangerously low. If for some reason you must choose between administering pure (100%) oxygen or giving a transfusion of whole blood to restore the red blood cell count, which would you expect to be more helpful? Address this decision by answering the questions below. Show your work and be as quantitatively explicit as possible.
b) One obviously can’t deliver oxygen at a concentration higher than 100%, but how else might the partial pressure of the oxygen being delivered be modified to increase the amount diffusing into the blood?