Blood Pressure Measurement | Sphygmomanometer

Accurately measuring blood pressure is a crucial skill in assessing patient health. Here we provide comprehensive guidance on how to use a sphygmomanometer effectively, including practice drills and case assessment.

Blood Pressure Cuff

A sphygmomanometer is a device used to measure blood pressure by wrapping an inflatable rubber cuff around the upper arm. A small, handheld air pump inflates it and as the pressure is released over time with an air valve, Korotkoff Sounds can be heard through a stethoscope which indicate changes in arterial flow.

Ventricular contraction pushes blood through the arteries causing a rise and fall of arterial pressure. The highest pressure point is the systolic pressure. It is followed by a decrease in pressure and when the lowest blood pressure point is reached, we can observe the diastolic pressure.

Blood pressure is measured as millimeters of mercury (mmHg). Blood pressure readings stated as two numbers: The systolic value is first, and then the diastolic value. For example, "122 over 78".

Types of Blood Pressure Cuffs

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

The Patient - Arm Position

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.
• 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).
• Blood pressure readings are reported as two numbers. The systolic value is first, and then the diastolic value. For example, "122 over 78".
• If the subject's pressure is elevated, take two additional blood pressure measurements, waiting a few minutes between measurements.
• Blood pressure ca rises as a result of the patient's stress level, smoking, recent exercise, exposure to cold temperatures and caffeinated drinks.
• 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, 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 underestimation 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.

General Guide to Blood Pressure Readings

• 140/90mmHg or higher indicates possible high blood pressure
• 120/80mmHg to 140/90mmHg indicates pre-high blood pressure
• 90/60mmHg up to 120/80mmHg indicates ideal blood pressure
• 90/60mmHg or lower indicates low blood pressure