Say a diastolic blood pressure reading was 80 mm Hg. This is consistent with which one of the following statements? A. the diastolic reading is 80 mm Hg greater than atmospheric pressure. B. pressure is measured in length units. C. the diastolic reading is 80 mm Hg less than atmospheric pressure. D. this is the maximum pressure produced by contraction of the myocardium.
Option A. Because atmospheric pressure (approximately 760 mmHg) is usually pres- ent, it's far taken to be a “relative zero” and different pressures are said as an amount more than atmospheric pressure. We say eighty implying eighty greater than 760, in preference to declaring 840 mmHg (760 eighty).
