Tonometer

Tonometer is a device that measures blood pressure using the so-called indirect method. We usually measure the blood pressure of the brachial artery (at the site of the nearest branch above the site where the cuff is applied). The arm should be at heart level so that the hydrostatic blood pressure does not affect the measurement.

Blood pressure
Blood pressure is the lateral pressure of flowing blood through which a blood column acts on a vessel wall. It fluctuates in the arteries, in the capillaries and veins it is constant and almost zero. So we are talking more about arterial pressure.


 * the ventricular systole pressure value and the diastole blood pressure value are recorded (eg 120/80 mmHg)
 * optimal values:
 * systolic blood pressure 105 mmHg to 140 mmHg,
 * diastolic blood pressure 60 mmHg to 90 mmHg,
 * hypotension : pressure less than 105/60 mmHg,
 * hypertension : pressure exceeds 140/90 mmHg.

Stephen Hales, an English theologian, physicist and physiologist of plants, was the first to measure blood pressure in 1738. He measured and compared the pressures of plant fluids and the blood of horses and dogs.

Mercury tonometer
The mercury tonometer (sphygmomanometer) consists of a manometer and an inflation system (balloon with a discharge valve).

We wind a cuff on the subject's arm, put on a stethoscope and hold the listening part of the stethoscope on the elbow hole (under the cuff). By squeezing the balloon, we increase the pressure to approximately 140 mmHg (the pressure values ​​are shown by the mercury column of the manometer). This will stop the blood flow through the artery. Then we gradually release the air from the cuff through the balloon valve.

Korotkov's sounds are created by the vibration of an artery due to the swirling blood flow. As the pressure in the cuff decreases, the vortex gradually ceases.
 * Systolic pressure value: the moment we hear the first sounds of flowing blood (so-called Korotkov sounds).
 * Diastolic pressure value: the moment Korotkov's sounds disappear.

The stethoscope is used to transmit sound from the examined area so that the volume of the transmitted sound is reduced as little as possible.

Aneroid tonometer (spring)
Sometimes a nine-volt battery speaker - Korotkov's sounds come from the speaker, mercury column replaced by resistance spring, the pressure values ​​on the scale are indicated by the hand, possible influence of the external environment on the properties of the spring.

Wrist digital automatic oscillometric instruments
Artery oscillation detection (pressure values ​​at the largest pressure changes), determination of the value of the so-called mean arterial pressure, the limits are calculated by the software of the device, possible inaccurate values ​​(principle of operation + less elasticity of the arteries at an older age).

There is a certain measurement deviation for each measuring instrument.

In practice
People should see a GP regularly and not rely solely on home measurements. The doctor measures the pressure more accurately, usually with a mercury pressure gauge.

There is currently talk of replacing mercury pressure gauges in medical surgeries with digital pressure gauges, where mercury is replaced by an electronic chip. These instruments have an accuracy quite comparable to mercury pressure gauges, measuring faster and easier to use.

Related articles

 * Blood pressure
 * Systolic blood pressure
 * Diastolic blood pressure
 * Blood pressure measurement
 * Heart revolution
 * Home blood pressure monitoring

Source

 * NOVOTNÝ, Ivan and Michal HRUŠKA. Human biology for grammar schools. 4th edition. Prague: Fortuna, 2007. 240 pp.  ISBN 978-80-7373-007-9.
 * FEJFAR, Zdenek. Hearts known and unknown. 1st edition. Mladá fronta, 1987. 222 p.
 * ZITKO, Miroslav. Internship in medical biophysics. 1st edition. Prague: Triton, 2003.  ISBN 80-7254-435-7.
 * BENEŠ, Jiří, et al. Basics of medical biophysics. 3rd edition. Prague: Karolinum, 2011.  ISBN 978-80-246-2034-3.
 * Wikipedia: The open encyclopedia. Blood pressure measurement [online]. [feeling. 2012-11-04]. < https://cs.wikipedia.org/wiki/M%C4%9B%C5%99en%C3%AD_krevn%C3%ADho_tlaku >.
 * Gymnasium and Secondary Vocational School of Education Znojmo. Circulatory system, heart activity [online]. [feeling. 2012-11-04]. < http://skolajecna.cz/biologie/Sources/Textbook_Textbook.php?intSectionId=31800 >.
 * ws:Tonometr