Taking Blood Pressure

Welcome to our blood pressure pages. On this page we present an explanation of blood pressure cuffs; how to take blood pressure; adult and pediatric assessment guides; practice drills for hypertension in children; and a series of case studies.

Blood Pressure Cuff

A blood pressure cuff is used to take blood pressure. The cuff has an inflatable rubber bladder that is fastened around the arm. A pressure meter indicates the cuff's pressure. A small, handheld air pump inflates the blood pressure cuff. After the cuff has been inflated an air valve is used to slowly release air pressure. As the pressure is released, a stethoscope is used to listen to arterial blood flow sounds.

The heart's beating pushes blood through the arteries causing a rise and fall of arterial pressure. The highest pressure is called systolic pressure and is followed by a decrease in pressure. This low blood pressure point is called the diastolic pressure.

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 this sounds are initially head, 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

The patient's blood pressure can be taken while the patient is supine, seated, standing. In the common seated position, the patient's arm should be at the level of the heart. The arm should be supported and flexed a little. If the subject is anxious, wait a few minutes before taking the pressure.

Procedures

• Use a properly sized blood pressure cuff. The length of the cuff's bladder should be at least equal to 80% of the circumference of the upper arm.
• Wrap the cuff around the upper arm with the cuff's lower edge one inch above the antecubital fossa.
• Lightly press the stethoscope's bell over the brachial artery just below the cuff's edge. Some health care workers have difficulty using the bell in the antecubital fossa, so we suggest using the bell or the diaphragm to measure the blood pressure.
• Rapidly inflate the cuff to 180mmHg. Release air from the cuff at a moderate rate (3mm/sec).
• Listen with the stethoscope and simultaneously observe the sphygmomanometer. 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).
• Record the pressure in both arms and note the difference; also record the subject's position (supine), which arm was used, and the cuff size (small, standard or large adult cuff).
• If the subject's pressure is 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.