Sphygmomanometer
A sphygmomanometer, also known as a blood pressure meter or sphygmometer, is
a tool used for measuring blood pressure. It comprises an inflatable cuff to
constrict blood flow and a mercury or mechanical manometer to gauge the
pressure. Typically, it is utilized alongside a method to ascertain when
blood flow commences and when it resumes unrestrictedly. Manual
sphygmomanometers are paired with a stethoscope for use.
The term originates from the Greek words sphygmós (pulse) and the scientific
term manometer (pressure meter). It was invented by Samuel Siegfried Karl
Ritter von Basch in 1881. A more user-friendly version was introduced by
Scipione Riva-Rocci in 1896, and in 1901, Harvey Cushing modernized and
popularized the device within the medical community.
A sphygmomanometer comprises an inflatable cuff, a measuring unit (either a
mercury manometer or an aneroid gauge), and an inflation bulb and valve for
manual instruments. In humans, the cuff is typically wrapped snugly around
the upper arm, positioned at the level of the heart while the individual is
seated with their arm supported. Correct cuff sizing is crucial, as using a
cuff that is too small can lead to falsely elevated readings, while a cuff
that is too large can result in inaccurately low readings.
To measure blood pressure, the cuff is inflated until arterial flow is
occluded. As the cuff pressure is gradually released, the examiner listens
with a stethoscope for the Korotkoff sounds, indicating the resumption of
blood flow. The pressure at which the sounds first appear is recorded as the
systolic blood pressure, while the pressure at which they disappear is
recorded as the diastolic blood pressure. Alternatively, in noisy
environments where auscultation is challenging, systolic pressure may be
determined by palpating the radial pulse.
Observing the mercury column while releasing air pressure allows for the
reading of blood pressure values in millimeters of mercury (mm Hg). Systolic
pressure, the peak pressure during the cardiac cycle, is identified by the
onset of continuous Korotkoff sounds, while diastolic pressure, the lowest
pressure during the resting phase of the cardiac cycle, is identified when
the Korotkoff sounds cease.
Blood pressure measurement is essential in diagnosing and treating
hypertension and various other medical conditions.
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