Auscultatoric measurement devices

Auscultatoric measurement devices determine blood pressure by monitoring Korotkoff sounds. An inflatable cuff is placed around the upper arm at roughly the same vertical height as the
heart, normally attached to a mercury manometer. The cuff is fitted and infl ated manually by squeezing a rubber bulb or - as it is the case in Tensoval duo control automatically
until the artery is completely occluded (about 30 mmHg above the systolic pressure). Then the pressure in the cuff is slowly released. When blood starts to fl ow in to the artery, the turbulent flow creates a pulse synchronic pounding (first Korotkoff sound). The pressure at which this sound is first detected is the systolic blood pressure. The cuff pressure is further released until no more sound can be detected at the diastolic arterial pressure.

 

Quicksilver-sphygmomanometer

Auscultatoric measurement devices

This sort of blood pressure measurement device is called the „'olden standard' of blood pressure measurement because it is highly reliable and accurate. This is why it is predominantly used as a reference system in clinical validation studies. Due to its toxicological and ecological characteristics (keyword: quicksilver) its use is limited by governmental authorities in most of the countries of the European Union or its use even prohibited.
The underlying measurement principle is the same is the one of stethoscopes.

 

Stethoscope

Auscultatoric measurement devices

Stethoscopes are mainly used in the doctors’ office because of their reliability and accuracy. In contrast to quicksilver-sphygmomanometers the pulse signals are transformed into readable values by a mechanical technology.

Mode of functioning
A sphygmomanometer usually consists of an inflatable cuff, a measuring unit (the manometer), a tube to connect the two, and (in models that don't inflate automatically) an inflation bulb also connected to the cuff by a tube. The inflation bulb contains a one-way valve to prevent inadvertent leak of pressure while there is an adjustable screw valve for the operator to allow the pressure in the system to drop in a controlled manner.
The cuff is placed around the upper arm, at roughly the same vertical height as the heart while the subject is in a sitting position. The cuff is inflated until the artery is completely occluded. Listening with a stethoscope to the brachial artery at the elbow, the examiner slowly releases the pressure in the cuff. As the pressure in the cuffs falls, a "whooshing" or pounding sound is heard (Korotkow sounds) when bloodflow first starts again in the artery. The pressure at which this sound began is noted and recorded as the systolic blood pressure. The cuff pressure is further released until the sound can no longer be heard and this is recorded as the diastolic blood pressure.

Stethoscope measurement at the doctor's office: the correct measurement process