Blood pressure, or BP, typically is measured indirectly by auscultation or oscillometry. For auscultation, a stethoscope and a sphygmomanometer consisting of a blood pressure cuff and either a mercury column or an aneroid manometer are used. When you are first learning as a student, it is highly recommended that you practice with a trained BP technician or physician using a dual- or multiple-head stethoscope so you can listen simultaneously and compare BP readings for the same trial.
Step 1
Seat the patient and have him place his arm on a table or on your shoulder so that the middle of the arm is at the level of the patient's heart. Estimate the patient's arm circumference and choose a cuff size accordingly.
Step 2
Palpate the brachial artery pulse on the anteriomedial aspect of the arm below the biceps brachii muscle. Wrap the deflated cuff firmly around the upper arm so that the indicated midline of the cuff is directly over the brachial pulse.
Step 3
Make sure the valve at the end of the dial is screwed shut. Rapidly inflate the cuff to 70 mmHg then slowly increase the pressure in 10-mmHg increments while palpating the radial pulse. When the pulse disappears, this is the estimated systolic BP. Partially open the valve by unscrewing it to slowly release pressure at a rate of 2 to 3 mmHg/sec, noting when the pulse reappears to estimate diastolic BP.
Step 4
Position the earpieces of the stethoscope over the brachial pulse. Close the valve quickly and steadily inflate the cuff pressure to about 20 to 30 mmHg above the estimated systolic pressure previously determined by palpation. Partially open the valve to slowly release pressure at a rate of 2 to 3 mmHg/sec. The first sharp thud is known as the first Korotkoff sound, which corresponds to the systolic pressure.
Step 5
Continue reducing the pressure slowly, noting when the metallic tapping sound becomes muffled, which is Phase IV diastolic pressure, and when the sound disappears, or Phase V diastolic pressure. Proceed by deflating the cuff for at least 10 mmHg, making certain no additional sounds are heard. Then rapidly deflate the cuff.
Tips and Warnings
- While the cuff does not have to be applied to bare skin, clothing around the arm should be thin. Record all values, then wait 30 seconds before repeating the measurement. Use the average of the two measurements for each value.
References
- "Advanced Fitness Assessment and Exercise Prescription"; Vivian H. Heyward, PhD; 2006
- American Heart Association: Blood Pressure Testing and Measurement
