Appendix; Principle Of Blood Pressure Measurement - A&D TM-2441 Instruction Manual

11.

Appendix

11.1. Principle of Blood Pressure Measurement

Measurement procedure: Wrap the cuff around the upper arm.
Inflate the cuff to a pressure exceeding the systolic blood pressure.
Then, exhaust the air from the cuff gradually. While the pressure is
detected in the cuff in the air exhaustion stage, the pulse waveform
appears in synchronization with the heartbeat. The pulse waveform
suddenly increases near the systolic blood pressure. It increases
further with exhaustion until it reaches its highest amplitude, then
decreases gradually. The changes in the pulse waveform are
illustrated on the next page. In oscillometric blood pressure
measurement, the systolic blood pressure is specified as the point
where the amplitude increases suddenly after the pulse in the cuff
pressure is detected, while the mean blood pressure is specified as
the point where the amplitude reaches its maximum and the diastolic
blood pressure is specified as the point where the amplitude
decreases gradually. Actually, the pressure sensor detects subtle
changes in the cuff pressure over time, stores the pulse waveform
in memory and evaluates the systolic and diastolic blood pressures
according to the oscillometric measurement algorithm. The details in
the algorithm vary with the blood pressure monitor. Blood pressure
values for adults and infants are measured by the oscillometric
method and are compared with those measured by the auscultatory
method. Diastolic blood pressure is defined as the end point of
phase 4 in the auscultatory method. The pulse waveform of the
cuff pressure depends on the characteristics of the cuff material.
Therefore, by using the specified cuff and the measurement
algorithm, the measurement accuracy is maintained. The air hose
length is less than 3.5 m, because of the damping characteristics
due to pulse wave propagation.
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