System Processing Description
ARGUS VCM
NIBP Processing
Overview
The oscillometric technique does not use Korotkoff sounds to determine blood
pressure. The oscillometric technique monitors the changes in cuff pressure caused by
the flow of blood through the artery. The monitor inflates the cuff to a pressure that
occludes the artery. Even when the artery is occluded, the pumping of the heart against
the artery can cause small pressure pulses in the cuff baseline pressure. The monitor
lowers cuff pressure at a controlled rate. As the cuff pressure goes down, blood starts
to flow through the artery. The increasing blood flow causes the amplitude of the
pressure pulses in the cuff to increase. These pressure pulses continue to increase in
amplitude with decreasing cuff pressure until they reach a maximum amplitude at
which point they begin to decrease with decreasing cuff pressure. The cuff pressure at
which the pulse amplitude is the greatest is known as Mean Arterial Pressure(MAP).
The manner in which the pulse amplitudes vary is often referred to as the pulse
envelope. The envelope is an imaginary line that connects the peak of each pressure
pulse and forms an outline. The shape of the envelope is observed by the monitor
using a variety of techniques to determine the diastolic and systolic blood pressure.
●
Oscillometric Response
(Pressure Pulses)
●
Cuff Pressure
Systole
Systole
MAP
Distole
MAP
Distole
Distole
MAP
Syst
ole
TIME
TIME
Overall Accuracy Discussion
Overall system accuracy shall be determined by considering various influences of the
pressure sensor accuracy, motion artifacts and other artifact created by pressure valve,
technical errors of electrical components, and the origin error of oscillometric method.
The origin error of oscillometric comes from the basic theory of that the MAP is
determined by the pulse. Therefore, there might be an error of the time between two
pulses. In another words, the greatest amplitude point of pulses could not represent
the MAP point exactly.
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ARGUS VCM
Service Manual
