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sphygmomanometer

sphygmomanometer

The word comes from the Greek σφυγμός (sphygmos, pulse), plus the scientific term manometersphygmomanometer blood pressure meterblood pressure monitor orblood pressure gauge (also referred to as a sphygmometer) is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner,[2] and a mercury or mechanicalmanometer to measure the pressure. It is always used in conjunction with a means to determine at what pressure blood flow is just starting, and at what pressure it is unimpeded. Manual sphygmomanometers are used in conjunction with a stethoscope.

 

A brief history of sphygmomanometer

blood pressure machines are fairly ubiquitous in today’s world, found not only in the doctor’s office but in the pharmacy section of many national chain stores, this important diagnostic instrument only emerged in the late nineteenth century.  The ability to measure blood pressure took over two hundred years to develop.

The measurement of blood pressure began in 1733 when Stephen Hales demonstrated that the amount of pressure generated by the heart could be measured through the displacement of blood.  Using a horse as his subject, he inserted a pipe into an artery and attached this to a glass tube, into which blood would flow and could be measured.  The invasive nature of this procedure meant that it had little clinical application with humans.

In 1828, Jean Leonard Marie Poiseuille introduced the mercury manometer, or as he called it the haemodynamometer, as a key tool for measuring blood pressure.  Manometers, first invented in the seventeenth century to measure pressure, were typically U-shaped tubes containing mercury or some other liquid.  In Poiseuille’s experiment, a cannula, or hollow tube with retractable inner core, was inserted into an artery and attached to a manometer on the other end.  With each pulse, the movement of blood displaced mercury inside the manometer.  Blood pressure was identified by measuring the amount of mercury displacement.

In 1847 this technique was advanced when Carl Ludwig invented the kymograph, an instrument that allowed for the graphic representation of data.  Essentially, the manometer was attached to a float pen connected to a revolving drum.  As the mercury moved with each pulse, so too the pen moved, creating a wave chart depicting each pulse on the drum.

 

The problem with both of these methods was that they required invasive measures, tubes being inserted into arteries.  Beginning in 1855 new indirect and non-invasive methods of assessing blood pressure were attempted, based primarily on the idea of assessing the counter-pressure needed to stop circulation.  In 1860 Etienne Jules Marey measured blood pressure by enclosing the arm in a water-filled glass chamber and increasing the water pressure until no circulation occurred.  The pressure at this point was identified as the systolic pressure.  In 1881, Samuel Siegfried Karl Ritter von Basch improved upon the method.  He placed a rubber bag around a manometer bulb and inflated the bag with water.  As the water enabling the measurement of the pressure.  The bag was placed over the distal pulse and inflated until the pulse was no longer recorded; the pressure at this point was noted as the systolic pressure.  In 1889 Pierre Potain altered this method by using air rather than water in the compression bag.

Blood pressure measurement evolved again in 1896, becoming much use of a cuff placed around the arm’s circumference, which was inflated by an attached bulb.  The pressure in the cuff was increased until the radial pulse (at the wrist) was no longer present.  At this point, the pressure in the cuff was released.  The pressure at which the radial pulse reappeared was noted as the systolic pressure

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twentieth century it was possible to calculate systolic pressure, but diastolic pressure remained elusive.  The ability to measure diastolic pressure was first achieved in 1905 by Nikolai Korotkoff.  He the blood in the arteries and associated with changes in pressure that doctors and nurses now use to read blood pressure.  These sounds are what your physician is listening for when they hold a stethoscope to your inner elbow when taking your blood pressure.  They read the pressure gage on the sphygmomanometer when they hear Korotkoff sounds to identify your systolic and diastolic readings.  When the blood pressure cuff is inflated and occluding blood flow no sounds are heard.  The first sound is heard when systolic pressure is reached and some blood is able to pass through the artery, but does so in spurts as the pressure varies from being above to below the pressure in the cuff with each heart beat.  This variance causes the blood to flow turbulently and make audible sounds.  As the pressure in the cuff continues to lower, the sounds diminish and ultimately disappear once a consistent blood flow is established.  The pressure reading at this moment is considered the diastolic pressure.


 

 

Posted on 07/09/2017 0 684

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