Manual blood pressure measurement offers a direct way to assess cardiovascular health. This technique involves using a stethoscope to listen for specific sounds, known as Korotkoff sounds, produced by blood flow in the arteries. Understanding this method provides insight into the pressure exerted by blood against artery walls, allowing for precise readings.
Essential Equipment
To measure blood pressure manually, two primary tools are necessary: a sphygmomanometer and a stethoscope. A sphygmomanometer comprises an inflatable cuff, a pressure gauge (manometer), and a bulb for inflation. The cuff temporarily restricts blood flow, and the gauge displays the pressure in millimeters of mercury (mmHg). The bulb inflates the cuff, and a valve allows for controlled deflation.
A stethoscope amplifies internal body sounds, making Korotkoff sounds audible. It features eartips, ear tubes, and a chest piece, which typically includes both a diaphragm and a bell. The diaphragm is generally used for higher-pitched sounds, while the bell is suited for lower-pitched sounds, like those associated with blood pressure measurement.
Step-by-Step Measurement
For accurate results, proper patient preparation is important. The individual should sit comfortably with their back supported and feet flat on the floor, avoiding crossed legs. They should rest quietly for at least five minutes beforehand and avoid caffeine, exercise, or smoking for 30 minutes prior. The arm chosen for measurement should be bare, free of clothing, and positioned at heart level with the palm facing upward.
Apply the blood pressure cuff snugly around the upper arm, approximately one inch above the bend of the elbow. The cuff should be correctly sized for the arm, allowing only two fingertips to comfortably slip underneath its top edge when deflated. Locate the brachial artery, typically found on the inner side of the arm near the elbow crease, and ensure the cuff’s artery marker is aligned over this artery.
Place the stethoscope’s chest piece, specifically the diaphragm or bell, lightly over the brachial artery in the elbow crease. Ensure the earpieces of the stethoscope are pointing forward, towards your nose. With the stethoscope in place, rapidly inflate the cuff by squeezing the bulb until the gauge reads about 30 mmHg above the person’s typical systolic pressure, or to around 160-180 mmHg if the usual pressure is unknown.
After inflation, slowly release the air from the cuff at a rate of approximately 2-3 mmHg per second by turning the valve on the bulb. As the pressure gradually decreases, listen carefully through the stethoscope for the first faint, repetitive tapping sounds. The reading on the pressure gauge at this moment marks the systolic blood pressure.
Continue to slowly deflate the cuff and listen as the sounds become muffled, then disappear completely. The point where the sounds fully disappear indicates the diastolic blood pressure. Once both readings are recorded, fully deflate the cuff and remove it from the arm.
Understanding Your Readings
Blood pressure readings consist of two numbers: systolic and diastolic. The systolic pressure, the upper number, represents the pressure in the arteries when the heart contracts and pumps blood. The diastolic pressure, the lower number, reflects the pressure in the arteries when the heart rests between beats.
The sounds heard during manual blood pressure measurement are known as Korotkoff sounds, which arise from turbulent blood flow as the cuff deflates. These sounds have distinct phases.
General blood pressure categories, according to the American Heart Association (AHA), define normal blood pressure as less than 120 mmHg systolic and less than 80 mmHg diastolic. Elevated blood pressure ranges from 120-129 mmHg systolic and less than 80 mmHg diastolic. Stage 1 hypertension is 130-139 mmHg systolic or 80-89 mmHg diastolic, while Stage 2 hypertension is 140 mmHg systolic or higher, or 90 mmHg diastolic or higher.
Ensuring Accurate Results
To ensure accurate results, always use a cuff that is the appropriate size for the individual’s arm, as an incorrect size can lead to inaccurate readings. The patient should remain still and quiet during the measurement, as talking or movement can influence the readings.
The deflation rate of the cuff is also important; aim for a steady release of air at about 2-3 mmHg per second. Releasing the air too quickly can cause you to miss the precise points for systolic and diastolic pressures. Taking multiple readings, ideally two or three, with a brief rest period of one to two minutes between each, can provide a more representative average. Recording the readings immediately helps prevent errors.