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How do blood pressure monitors really work?

How do blood pressure monitors really work?

Blood pressure monitors are common a sight, be it outpatient areas or hospital wards. They are in use every day, but everyday people do not know how they actually work. Let’s look into how blood pressure measuring devices function, with a little history.


Italian physician Scipione Riva-Rocci developed an auscultation technique (listening to the internal sounds of the body) in 1896 which required only a stethoscope and an arm cuff hooked up to a manometer. 

The method was not very difficult. The arm cuff is pumped full of air, that cuts off the circulation in the brachial artery, and the pressure is then released gradually. The blood flow remains turbulent for as long as the artery is partially compressed. A noise phenomenon known as Korotkoff sounds comes as a result, which can be counted by placing a stethoscope on the brachial artery or by installing a noise enhancer into the cuff.

Systolic blood pressure readings can be taken from the manometer as soon as they occur. The sounds disappear when compression of the artery is released fully and the blood can flow again. The pressure that can now be measured in the cuff is known as the diastolic blood pressure.



With the passage of time and advancement in medicinal techniques, however, the auscultation technique has how been widely replaced by automatic blood pressure monitoring devices. The automation and simplicity of the hardware has made these devices fit and friendly for home use as well. There is only one major difference in the operating principles of the model developed by Riva-Rocci and the modern blood pressure monitoring devices. The former records the resultant sounds and the latter records vibrations or oscillations of the vascular walls of the arteries.

Same as with the auscultatory method, blood flow through the artery returns when the cuff pressure falls below systolic blood pressure level. Vibrations in the artery walls are caused due to the turbulent, the maximum of which correlates with what is known as ‘mean arterial pressure’, or ‘MAP’. The so mentioned vibrations are detected by the sensors in the arm cuff. If the cuff pressure drops below the diastolic pressure, the vibrations stop. A record is created based on the changing oscillation amplitude between systolic and diastolic blood pressure.

It has been proven that detecting oscillation maximum is easier than it is to start and stop it, hence the MAP (mean arterial pressure) constitutes the most reliable figure for automatic blood pressure measurement. Systolic and diastolic blood pressure can also be calculated using the appropriate algorithms, the oscillogram and the MAP. However, there may be differences in measurement between individual devices and manufacturers. 

Irrespective of whether blood pressure checks are performed digitally or in the old fashioned way, they are important for basic healthcare of every individual. Many problems like heart attacks and strokes can be effectively avoided if high blood pressure is detected early on. It may help save a life from premature death. Prevention and treatment of high blood pressure includes physical exercise, a change in diet and weight loss or medication.


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