Are you measuring transmural pressure or perfusion pressure, for example, when you determine blood pressure in the arm with a cuff, stethoscope, and sphygmomanometer? The answer of course is transmural pressure! To measure perfusion pressure you have to measure transmural pressures at two different points in the circulation; for example, at the brachial artery and then at a vein which is returning blood to the heart. The difference between the two values yields the perfusion pressure. [SEE MISCONCEPTION 11]