Blood pressure measurement

Blood-Pressure Measurement
Jonathan S. Williams, M.D., M.M.Sc., Stacey M. Brown, M.S., and Paul R. Conlin, M.D.
Indications
From the Medical Service, Veterans Affairs Boston Healthcare System (J.S.W., P.R.C.); the Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital (J.S.W., S.B., P.R.C.); and Harvard Medical School (J.S.W., P.R.C.) — all in Boston. N Engl J Med2009;360:e6.
Copyright © 2009 Massachusetts Medical Society.

Blood-pressure measurement is indicated in any situation that requires assessment of cardiovascular health, including screening for hypertension and monitoring the effectiveness of treatment in patients with hypertension. In the routine outpatient setting, blood-pressure measurement is obtained indirectly. Proper techniques areimportant to ensure consistent and reliable measurements.
Contraindications

Measurement of blood pressure at the brachial artery is a generally benign procedure. However, there are some circumstances in which obtaining readings from a particular arm may not be appropriate; such circumstances include the presence of an arterial–venous shunt, recent axillary node dissection, or any deformity orsurgical history that interferes with proper access or blood flow to the upper arm. If these relative contraindications are present, blood pressure should be assessed in the opposite arm. There may also be pre-existing conditions that can interfere with the accuracy or interpretation of readings, such as aortic coarctation, arterial–venous malformation, occlusive arterial disease, or the presence of anantecubital bruit. If neither arm can be used, then measurement of blood pressure in a leg may be indicated.
Equipment

The essential equipment for blood-pressure measurement includes a stethoscope and a sphygmomanometer. The stethoscope tubing should be long enough to permit the practitioner to auscultate Korotkoff sounds while viewing the manometer at eye level. Use of the bell side of thestethoscope chestpiece facilitates auscultation of the low-frequency Korotkoff sounds. The sphygmomanometer consists of a blood-pressure cuff containing a distensible bladder, a rubber bulb with an adjustable valve for inflation, tubing that connects the cuff to the bladder, and a manometer (Fig. 1). Regular inspection and calibration of the equipment are important to ensure that it is in properworking order. For accurate measurement, calibrations are recommended every 6 months.1,2 Many institutions have removed mercury manometers from clinical settings and replaced them with aneroid manometers. The steps required for accurate bloodpressure measurement with an aneroid or a mercury manometer are identical.
Preparation
Figure 1. Equipment used in bloodpressure measurement.

Theexamination room should be quiet, with a comfortable ambient temperature. Ideally, blood pressure should not be measured if the patient has engaged in recent physical activity, used tobacco, ingested caffeine, or eaten within the past 30 minutes.3

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Blood-Pressure Measurement

Positioning of the Patient

Correct positioning of the patient is essential for accurate measurement. The patient’s back and legs should be supported, with the legs uncrossed and the feet resting on a firm surface. The arm in which blood pressure will bemeasured should be bare to the shoulder, and the garment sleeve, if raised, should be loose, so that it does not interfere with blood flow or with proper positioning of the blood-pressure cuff. The arm should be supported and level with the heart. The manometer should be positioned at the health care practitioner’s eye level.
Arm Measurement

A common error in measuring blood pressure is the...