instrument for measuring blood pressure. It consists of an inflatable rubber cuff, which is wrapped around the upper arm and is connected to an apparatus that records pressure, usually in terms of the height of a column of mercury or on a dial. An arterial blood pressure reading consists of two numbers, which typically may be recorded as x/y. The x is the systolic pressure, and y is the diastolic pressure. Systole refers to the contraction of the ventricles of the heart, when blood is forced from the heart into the pulmonary and systemic arterial circulation, and diastole refers to the resting period, when the ventricles expand and receive another supply of blood from the atria. At each heartbeat, blood pressure is raised to the systolic level, and, between beats, it drops to the diastolic level. As the cuff is inflated with air, a stethoscope is placed against the skin at the crook of the arm. As the air is released, the first sound heard marks the systolic pressure; as the release continues, a dribbling noise is heard. This marks the diastolic pressure, which is dependent on the elasticity of the arteries.

Using a sphygmomanometer to measure a person's blood pressure is a routine part of every physical exam and has been for decades.  The results a sphygmomanometer provides can assess suitability for certain physical activities, predict long-term health risks, help manage many types of medical problems, and determine eligibility for insurance.  The use of a sphygmomanometer has been standard practice in the medical profession for over a century and will only continue to be.

The word comes from the Greek sphygmus (pulse) and manometer, an instrument used for measuring the pressure of liquids and gasses.  The sphygmomanometer was invented by Samuel Siegfried Karl Ritter von Basch and first appeared in doctors' surgeries in the 1880s.  In 1896, Italian pediatrician Scipione Riva-Rocci introduced an easy-to-use variation of the sphygmomanometer that consistently gave reliable results.  Harvey Cushing, recognized in the medical profession as the greatest neurosurgeon of the twentieth century, found Riva-Rocci’s sphygmomanometer on a visit to Pavia in 1901 and soon popularized it.

The modern aneroid sphygmomanometer has an inflatable cuff that is wrapped around the upper arm and inflated with air by repeatedly squeezing a rubber bulb.  When the pressure in the cuff gets high enough, blood flow in the main artery of the upper arm is cut off.  The air is then slowly released and as the pressure falls, a stethoscope is placed over the artery where the sound of rushing blood is heard.  These sounds are referred to as Korotkoff sounds.  The pressure at which sound is first heard is the systolic pressure.  The last sound heard is the diastolic pressure, the pressure at which the sound disappears as the blood resumes normal flow.

 

In order to obtain accurate blood pressure results using a sphygmomanometer, it’s important to make note of the following:

1. The inflatable part of the cuff must be the correct size for the arm.  It should cover two thirds of the length of the upper arm. A blood pressure cuff that’s too small will cause an abnormally high blood pressure reading and a low reading may result from too large a cuff.  The cuff should be firmly placed with the center of the inflatable part over the brachial artery. 

2. The cuff must be free of leaks. 

3. The mercury should be clean and at the zero mark before use. 

4. During cuff inflation, the mercury should rise smoothly and stop immediately inflation stops.

Sphygmomanometer

A sphygmomanometer is an inflatable cuff used to measure blood pressure. It is placed around the upper arm, at roughly the same vertical height as the heart in a sitting person, and attached to a manometer. The cuff is inflated until the artery is completely occluded. Listening with a stethoscope to the braRchial artery at the elbow, the examiner slowly releases the pressure in the cuff. When bloodflow barely begins again in the artery, a "whooshing" or pounding sound is heard (see Korotkoff sounds). The pressure is noted at which this sound began. This is the systolic blood pressure. The cuff pressure is further released until the sound can no longer be heard. This is the diastolic blood pressure. The peak pressure in the arteries during the cardiac cycle is the systolic pressure, and the lowest pressure (at the resting phase of the cardiac cycle) is the diastolic pressure.