What happens to the measured systolic pressure when the arm is raised above the head?

What happens to the measured systolic pressure when the arm is raised above the head?

• A. It is lower than in the normal position
• B. It is higher than in the normal position
• C. It remains the same
• D. It cannot be measured

Answer: (A)

Raising the arm above heart level changes the hydrostatic pressure in the blood. Gravity makes the pressure in vessels at a higher position lower than at the heart, so the cuff, sitting higher than the heart, reads a smaller arterial pressure. The systolic value drops by roughly 0.75 mmHg for each centimeter the arm is raised, so even modest elevation lowers the reading, sometimes by a noticeable amount. The measurement is still possible—it’s simply lower than in the normal position.

Raising the arm above heart level changes the hydrostatic pressure in the blood. Gravity makes the pressure in vessels at a higher position lower than at the heart, so the cuff, sitting higher than the heart, reads a smaller arterial pressure. The systolic value drops by roughly 0.75 mmHg for each centimeter the arm is raised, so even modest elevation lowers the reading, sometimes by a noticeable amount. The measurement is still possible—it’s simply lower than in the normal position.