Getting Ready To Measure Blood Pressure

Ideally, ask the patient to avoid smoking or drinking caffeinated beverages for 30 minutes before the blood pressure is taken and to rest for at least 5 minutes. Check to make sure the examining room is quiet and comfortably warm. Make sure the arm selected is free of clothing. There should be no arteriovenous fistulas for dialysis, scarring from prior brachial artery cutdowns, or signs of lymphedema (seen after axillary node dissection or radiation therapy). Palpate the brachial artery to confirm that it has a viable pulse. Position the arm so that the brachial artery, at the antecubital crease, is at heart level—roughly level with the 4th interspace at its junction with the sternum. If the patient is seated, rest the arm on a table a little above the patient's waist; if standing, try to support the patient's arm at the midchest level.

If the brachial artery is much below heart level, blood pressure appears falsely high. The patient's own effort to support the arm may raise the blood pressure.

Jow you are ready to measure the blood pressure. Center the inflatable ladder over the brachial artery. The lower border of the cuff should be wout 2.5 cm above the antecubital crease. Secure the cuff snugly. Position ie patient's arm so that it is slightly flexed at the elbow.

A loose cuff or a bladder that balloons outside the cuff leads to falsely high readings.

To determine how high to raise the cuff pressure, first estimate the systolic pressure by palpation. As you feel the radial artery with the fingers of one hand,

rapidly inflate the cuff until the radial pulse disappears. Read this pressure on the manometer and add 30 mm Hg to it. Use of this sum as the target for subsequent inflations prevents discomfort from unnecessarily high cuff pressures. It also avoids the occasional error caused by an auscultatory gap—a silent interval that may be present between the systolic and the diastolic pressures.

Deflate the cuff promptly and completely and wait 15 to 30 seconds.

Now place the bell of a stethoscope lightly over the brachial artery, taking care to make an air seal with its full rim. Because the sounds to be heard (Korotkoff sounds) are relatively low in pitch, they are heard better with the bell.

An unrecognized auscultatory gap may lead to serious underestimation of systolic pressure (e.g., 150/98 in the example on p._) or overestimation of diastolic pressure.

If you find an auscultatory gap, record your findings completely (e.g., 200/98 with an auscultatory gap from 170-150).

Inflate the cuff rapidly again to the level just determined, and then deflate it slowly at a rate of about 2 to 3 mm Hg per second. Note the level at which ou hear the sounds of at least two consecutive beats. This is the systolic yp p ressure.

Continue to lower the pressure slowly until the sounds become muffled and then disappear. To confirm the disappearance of sounds, listen as the pres-ire falls another 10 to 20 mm Hg. Then deflate the cuff rapidly to zero. The disappearance point, which is usually only a few mm Hg below the muffing point, enables the best estimate of true diastolic pressure in adults.

In some people, the muffling point and the disappearance point are farther apart. Occasionally, as in aortic regurgitation, the sounds never disappear. If there is more than 10 mm Hg difference, record both figures (e.g., 154/80/68).

Brachial Pulse Check

Read both the systolic and the diastolic levels to the nearest 2 mm Hg. Wait 2 or more minutes and repeat. Average your readings. If the first two readings differ by more than 5 mm Hg, take additional readings.

When using a mercury sphygmomanometer, keep the manometer vertical (unless you are using a tilted floor model) and make all readings at eye level with the meniscus. When using an aneroid instrument, hold the dial so that it faces you directly. Avoid slow or repetitive inflations of the cuff, because the resulting venous congestion can cause false readings.

Blood pressure should be taken in both arms at least once. Normally, there may be a difference in pressure of 5 mm Hg and sometimes up to 10 mm Hg. Subsequent readings should be made on the arm with the higher pressure.

In patients taking antihypertensive medications or patients with a history of fainting, postural dizziness, or possible depletion of blood volume, take the blood pressure in three positions—supine, sitting, and standing (unless con-traindicated). Normally, as the patient rises from the horizontal to a standing position, systolic pressure drops slightly or remains unchanged while diastolic pressure rises slightly. Another measurement after 1 to 5 minutes of standing may identify orthostatic hypotension missed by earlier readings. This repetition is especially useful in the elderly.

Definitions of Normal and Abnormal Levels. In 1997, the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure recommended that hypertension should be diagnosed only

By making the sounds less audible, venous congestion may produce artificially low systolic and high diastolic pressures.

Pressure difference of more than 10-15 mm Hg suggests arterial compression or obstruction on the side with the lower pressure. A fall in systolic pressure of 20 mm Hg or more, especially when accompanied by symptoms, indicates orthostatic (postural) hypotension. Causes include drugs, loss of blood, prolonged bed rest, and diseases of the autonomic nervous system.

when a higher than normal level has been found on at least two or more visits after initial screening. Either the diastolic blood pressure (DBP) or the systolic blood pressure (SBP) may be considered high. For adults (aged 18 or over), the Committee has categorized six levels of DBP and SBP:

Blood Pressure Classification (Adults)*

Category Systolic (mm Hg) Diastolic (mm Hg)


Category Systolic (mm Hg) Diastolic (mm Hg)


Stage 3 (severe)



Stage 2 (moderate)

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