Taking Blood Pressure

Explore our comprehensive blood pressure pages to gain a better understanding of cuff use, proper technique for taking readings, as well as practice drills and engaging case studies.

Blood Pressure Cuff

Taking a blood pressure reading with a sphygmomanometer is an easy process. The cuff, containing an inflatable rubber bladder, is placed around the arm and inflated by hand pump. As the pressure inside decreases with the release valve, arterial blood flow sounds are heard through a stethoscope. The patient's systolic and diastolic pressure are indicated on the cuff's dial or mercury level.

Each heart beat creates a rise and fall of arterial pressure as blood surges in the arteries. The high pressure point is the systolic pressure and is followed by a decrease in pressure. The diastolic pressure is the low blood pressure point.

When taking blood pressure, a stethoscope is positioned to listened to blood flow turbulence. The cuff is initially inflated well above expected systolic pressure. At this time, blood flow is stopped. No sounds are heard with the stethoscope. As the value is opened, pressure slowly diminishes.

When the cuff's pressure equals the arterial systolic pressure, blood begins to flow past the cuff. This creates blood flow turbulence and can be heard with the stethoscope. When these sounds are initially heard, the doctor or nurse makes a note of the cuff's air pressure value. As the cuff's air is continued to be released, the blood turbulence sounds continue to be heard. When the cuff's air pressure falls below the patient's arterial diastolic pressure, the sounds stop. This pressure when the blood flow sounds stop indicates the diastolic pressure.

Types of Blood Pressure Cuffs

There are mercury, aneroid (a mechanical dial) and digital blood pressure cuffs. Digital cuffs are automated while mercury and aneroid cuffs are used manually with a stethoscope.

The Patient

Commonly you will take the patient's blood pressure with the patient seated. Place the elbow as the same height as the heart. The arm should be supported and flexed a little. You can also take blood pressure when the patient is supine. If the subject is anxious, wait a few minutes before taking the pressure.

Procedures

• Begin by selecting blood pressure cuff with the correct size for the patient's arm.
• Place the cuff's lower edge one inch above the antecubital fossa and wrap it around the upper arm.
• The stethoscope's chestpiece should be lightly placed over the brachial artery, just below the cuff's edge.
• Quickly inflate the cuff to 30mmHg more that the patient's previous systolic pressure. Then release air from the cuff at a rate of 2 to 3 millimeters per second.
• Simultaneously observe the sphygmomanometer while listening with the stethoscope. The first knocking sound (Korotkoff) is the subject's systolic pressure. When the knocking sound disappears, that is the diastolic pressure (such as 120/80).
• In some clinics, you may be asked to record the pressure in both arms. You should make note of the subject's position, which arm, and the cuff size (small, standard or large adult cuff).
• If the subject's pressure is abnormally elevated, take two additional blood pressure measurements, waiting a few minutes between measurements.
• A BLOOD PRESSURE OF 180/120mmHg OR MORE REQUIRES IMMEDIATE ATTENTION!

Precautions

• Aneroid and digital manometers may require periodic calibration.
• Use a larger cuff on obese or heavily muscled subjects.
• Use a smaller cuff for pediatric patients.
• For pediatric patients a lower blood pressure may indicate the presence of hypertension.
• Don't place the cuff over clothing.
• Flex and support the subject's arm.
• In some patients the Korotkoff sounds disappear as the systolic pressure is bled down. After an interval, the Korotkoff sounds reappear. This interval is referred to as the "auscultatory gap." This pathophysiologic occurrence can lead to a marked under-estimation of systolic pressure if the cuff pressure is not elevated enough. It is for this reason that the rapid inflation of the blood pressure cuff to 180mmHg was recommended above. The "auscultatory gap" is felt to be associated with carotid atherosclerosis and a decrease in arterial compliance in patients with increased blood pressure.

Practice Taking Blood Pressure

• Use our blood pressure cuff simulator to practice taking blood pressure.
• Then take one of our courses that feature blood pressure, auscultation, and other physical examination skills.

Arterial Blood Pressure Assessment

Use the following link to learn more about measuring blood pressure and hypertension.

High Blood Pressure - Hypertension Guides

Measuring Blood Pressure Cases

We provide case-based training for measuring blood pressure using our simulator. The table of contents can be used to select a case.

Simple BP Drill

Use this link for a simplified practice drill.

Practice Drill