Blood Pressure Measurement | Sphygmomanometer

Taking Blood Pressure

Welcome to our blood pressure pages. 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

taking blood pressure

A sphygmomanometer is used to take blood pressure. The sphygmomanometer's 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. These sounds are called Korotkoff 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 diastolic pressure.

When taking blood pressure, a stethoscope is used to help the user hear 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 practitioner makes a note of the cuff's 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.

Blood pressure is measured in units of millimeters of mercury (mmHg). Blood pressure values (readings) should be stated as pairs. The higher (systolic) value first, and then the lower (diastolic) value. For example, "128 over 84". This is written as 128/84mmHg.


Types of Blood Pressure Cuffs

taking blood pressure

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







The Patient

taking blood pressure

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.
  • 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

Simplified Cases  

These simplified virtual patients allow you to focus solely on taking blood pressure.

Simplified Taking Blood Pressure Drill

Adult Cases

The adult case studies provide training for blood pressure reading using patient examples with our simulator. The adult case study course will teach you how to take blood pressure readings, heart and lung sounds, patient history and test results in order to establish a diagnosis and a treatment plan. The cases presented involve hypertension (high blood pressure), hypotension (low blood pressure), elevation of only systolic or diastolic pressures.

Adult Blood Pressure Cases - Part I

Adult Blood Pressure Cases - Part II

Pediatric Cases

These cases build assessment skills by simulating blood pressure measurement by auscultation. Users will also practice the evaluation of hypertension using the NIH's classification tables for children.

Pediatric Blood Pressure Course



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