Measuring Blood Pressure

Equipment

1. Stethoscope NOTE: Do not wear a stethoscope around your neck. There is a slight risk that you can entangle it in intravenous and other lines. There is also a risk that a psychotic or delirious patient could use it to harm you. Also, wearing a stethoscope can be a source of cross-contamination. Use 70% alcohol or benzalkonium chloride wipes. For cleaning stethoscope before and after use. Clean all parts. 2. Sphygmomanometer with a cuff of the appropriate size. Refer to Clinical Insight 19-1. A cuff that is too small will produce a false-high reading; a cuff that is too large will produce a false-low reading. NOTE: This procedure describes the use of an aneroid manometer or an electronic measuring device.

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10. *Deflate the cuff slowly* (2 to 3 mm Hg per second or per beat), listening for the Korotkoff sounds as you deflate. Deflating the cuff slowly increases patient discomfort and may alter the reading. Deflating the cuff faster may cause errors in hearing the Korotkoff sounds. a. As you deflate the cuff, blood begins to flow rapidly through the partially open artery, producing turbulence that you will hear through the stethoscope as a tapping sound. Note the point on the manometer at which you hear the first sound. This is the systolic BP. (If you are using an electronic BP device, read the digital screen when the numbers appear. Follow the manufacturer's instructions.) The 1st Korotkoff sound is the systolic pressure. b. Continue deflating the cuff and note the level at which the sounds become muffled and disappear. The artery is no longer compressed and sound will disappear. Record the point at which the sound disappears as the diastolic pressure. The 5th Korotkoff sound (the disappearance of sound) is the diastolic BP in adults. The 4th Korotkoff sound (the muffling of sounds) is the diastolic BP in children. The American Heart Association recommends recording the first sound, muffling, and last sound in children younger than 13 years, pregnant women, and people with high cardiac output or peripheral vasoconstriction.

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11. If you need to repeat the measurement, deflate the cuff completely, and wait 2 minutes before reinflating it. Prevents venous congestion and false high readings.

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3. *Fully expose the arm*, being careful that clothing is not tight. Remove clothing rather than rolling up a sleeve. Note: There is some evidence to suggest that readings taken over sleeves do not affect blood pressure results, and that it may actually be preferable because of concerns about hygiene, privacy and religious beliefs (Pinar, Ataalkin, & Watson, 2010). While you are learning, and until there is more evidence, we advise that you will find it easier to hear the BP sounds on a bare arm. Clothing that is tight enough to restrict blood flow will alter the reading. 4. *Place the cuff on the upper arm.* a. Wrap the cuff snugly. b. Ensure that the cuff is totally deflated and palpate the brachial artery. c. Place the bottom edge of the cuff approximately 1 in. (2.5 cm) above the antecubital space. d. Place the center of the cuff bladder directly over the brachial artery (the center is often indicated with an arrow on the BP cuff). The center of the cuff bladder needs to be directly over the brachial artery to obtain an accurate reading. Loose application of the cuff results in overestimation of the pressure.

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5. *Place the stethoscope ear pieces in your ears, pointing slightly forward*. When the earpieces point slightly forward, they direct sound into the ear canal, making the sounds more audible. 6. *Palpate the brachial artery* on the arm with the cuff. (Use the radial artery for this step if you prefer.) For correct stethoscope placement.

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7. *Inflate the cuff*, as follows: a. Close the sphygmomanometer valve and inflate the cuff rapidly to about 80 mm Hg. b. Then palpate the pulse while you continue inflating in 10 mm Hg increments until you no longer feel the pulse. c. As you inflate the cuff, the artery is occluded as the pressure of the cuff exceeds the pressure in the artery. At that point, blood flow through the artery is halted, and no sound can be heard. Note the pressure at which the pulse disappears. d. Go to step 8 or the variation, as you prefer. Palpating the artery while inflating the cuff ensures that the cuff is inflated higher than the systolic BP. If the patient has an auscultatory gap, the systolic pressure can be mistakenly identified as lower than it actually is. Palpation is particularly important if the baseline systolic BP is unknown or if the patient is hypertensive. 8. *Continue inflating the cuff* to a pressure that is 20 to 30 mm Hg above the level at which the pulse disappeared. Move to Step 9. Helps ensure you will not miss an auscultatory gap or a faint first sound.

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9. Place the stethoscope over the brachial artery as follows: a. Be certain that the stethoscope tubing is not touching anything and that the diaphragm is not tucked under the edge of the cuff. When the tubing rubs against clothing, for example, it produces artifact sounds that make it difficult to hear the BP sounds. Placing the bell or diaphragm under the cuff can partially occlude the brachial artery, delaying the appearance of the Korotkoff sounds. b. Using the bell will enable you to hear BP sounds more accurately, especially at diastolic pressures. However, most people use the diaphragm because it is easily placed and because some stethoscopes do not have a bell.

Pre-Procedure Assessment

Check for factors or activities that may alter the readings. Caffeine, smoking, exercise, and stress can all elevate the BP. Be certain the patient has been lying or sitting for at least 5 minutes (30 minutes after strenuous exercise) and is relaxed. Check the previous recording, if any. Noting changes over time is important with all patient assessments. Because BP changes constantly and because so many factors affect it, you cannot draw conclusions from a single measurement.

Evaluation

Compare the BP reading with previous readings. Look for trends. Is the BP slowly decreasing (e.g., impending shock) or slowly increasing (e.g., hypervolemia)? Look for a corresponding change in pulse rate, indicating potential hypoxemia. If this is the first BP measurement for the client, check readings in both arms. A difference of 10 mm Hg or less is normal. Report any significant changes in the BP reading.

Procedure pt 1

Procedure Steps 1. *Clean the stethoscope before and after the procedure.* Although only a small percentage of microorganisms are pathogenic, cleaning can reduce the bacterial count by 94% to 100%. 2. *Position the patient comfortably*, ensuring that: a. The legs are uncrossed, the back is supported, and the feet are resting on the floor (if the patient is sitting in a chair); or that the patient is supine. This position allows for the most accurate reading. Crossing the legs may elevate the BP reading. b. The measurement arm is supported at heart level, slightly flexed, with the palm facing upward. The blood pressure will decrease if the arm is above the heart and increase if the arm is below the heart or not supported.

Delegation

You can delegate measurement of BP to the NAP if you conclude that the patient's condition and the NAP's skills allow. Perform the pre-procedure assessments. Inform the NAP of the site (e.g., radial, brachial) to use. Inform the NAP of any special considerations (e.g., not to place a BP cuff on the same side as the site of a mastectomy). Ask the NAP to record and report the BP to you, and to report immediately if it is outside normal limits (you must specify what is "normal" for each patient). Tell the NAP that if BP is elevated to note which arm, the patient's position during measurement, and activity immediately preceding the measurement.