Which of the following statements regarding blood pressure measurements is true?
ExplanationThe length and width of the blood pressure cuff bladder should be 80% and 40% of the arm’s circumference, respectively. A common source of error in practice is to use an inappropriately small cuff, resulting in a marked overestimation of true blood pressure, or an inappropriately large cuff, resulting in an underestimation of true blood pressure. The cuff should be inflated to 30 mmHg above the expected systolic pressure and the pressure released at a rate of 2–3 mmHg/sec. Systolic and diastolic pressures are defined by the first and fifth Korotkof sounds, respectively. Very low (even 0 mmHg) diastolic blood pressures may be recorded in patients with chronic, severe aortic regurgitation (AR) or a large arteriovenous fistula because of enhanced diastolic “run-of.” In these instances, both the phase IV and phase V Korotkof sounds should be recorded. Blood pressure is best assessed at the brachial artery level, although it can be measured at the radial, popliteal, or pedal pulse level. In general, measured systolic pressure increases and diastolic pressure decreases when measured in more distal arteries. Blood pressure should be measured in both arms, and the difference should be less than 10 mmHg. A blood pressure differential that exceeds this threshold may be associated with atherosclerotic or inflammatory subclavian artery disease, supravalvular aortic stenosis, aortic coarctation, or aortic dissection. Systolic leg pressures are usually as much as 20 mmHg higher than systolic arm pressures. Greater leg–arm pressure differences are seen in patients with chronic severe AR as well as patients with extensive and calcified lower extremity peripheral arterial disease. The ankle-brachial index (lower pressure in the dorsal pedis or posterior tibial artery divided by the higher of the two brachial artery pressures) is a powerful predictor of long-term cardiovascular mortality. The blood pressure measured in an office or hospital setting may not accurately reflect the pressure in other venues. “White coat hypertension” is defined by at least three separate clinic-based measurements >140/90 mmHg and at least two non–clinic-based measurements <140/90 mmHg in the absence of any evidence of target organ damage. Individuals with white-coat hypertension may not benefit from drug therapy.
