When discussing the physiology of blood pressure with a group of assistive personnel, which statement is correct?

• A. Diastolic blood pressure reflects the pressure exerted during contraction of the heart.
• B. Blood pressure is measured and documented in millimeters of mercury.
• C. Blood pressure decreases when the blood viscosity increases.
• D. Systolic blood pressure reflects the pressure when the heart is relaxed.

Answer: (B)

Measuring blood pressure uses a unit that comes from the height of a mercury column, reflecting arterial pressure. Readings are given as systolic over diastolic and are reported in millimeters of mercury (mmHg). This makes the statement about the unit the correct one, since mmHg is the standard way we document blood pressure in clinical practice.

Understanding the rest helps reinforce the concept: diastolic pressure is the pressure when the heart is relaxed, not contracting. Systolic pressure is the pressure when the heart is contracting, not relaxed. Higher blood viscosity increases resistance to blood flow, which tends to raise, not lower, blood pressure.