Pulsewave Blood Pressure Measurement
Working Principle of
Instead of Korotkoff sound, the Pulsewave Blood Pressure Monitors apply upper bladder plus lower bladder detecting pulse wave, which can truly represents the state of blood flow. Instead of a single point measurement, multi-points measurement is applied. By using internal relations and variation between systolic and diastolic blood pressure, the approximation and fitting calculation method to calculate the true systolic and diastolic blood pressure, the Pulsewave Blood Pressure Monitor achieves a continuous measurement but non-continuous time, which can be measured heart blood pressure between the two consecutive hops instead of statistical data based on experience, avoiding measurement errors caused by individual differences.
SBP Measurement Principle
When measuring, the bladder deflates gradually. Amplitudes around the SBP are almost linear variation. SBP can be determined after real time processed to several pulse wave amplitudes and their correspondent bladder pressure. Because of pulse wave detection, non synchronous situation between sound and pulse does not exist. Therefore, pseudo low blood pressure can be evitable.
Pss0= (H2 x Pss1 - H1 x Pss2) / (H2-H1) ; ··· ··· (1)
In the formula (1):
Pss0 is the precise systolic, when bladder pressure equals Pss0, blood flow just changes the state
from completely blocked to gradually blocked;
Blood flows again, pulse wave amplitude H0 equals 0 at this moment;
H1 is pulse wave amplitude when cuff pressure is Pss1;
H2 is pulse wave amplitude when cuff pressure is Pss2;
DBP Measurement Principle
When measuring, there is regular variation of lag between pressure signal from upper bladder and pulse wave signal from lower bladder. The lag decreases before DBP point and become relatively stable after reaches DBP point. According to the time characteristics of the lag around the DBP, we process several lag of pulses and their correspondent bladder pressure in real time, then the DBP can be determined.
(Psz3-Psz0) : (T3-T0) = (Psz2-Psz0) :
(T2-T0) = (Psz1 - Psz0) : (T1-T0) ; ··· ··· (3)
There are at least continuous two point’s data of lag between bladder pressure, pulse wave and pressure signal generally appear to be a fixed value.
Psz0>PszA>PszB; ··· ··· (4)
T0= (TA+TB) /2; ··· ··· (5)
The intersection of oblique line and horizontal line in the time characteristics curve determines the diastolic blood pressure.
In the formula(3),(4)
Pss0 is the precise diastolic, which is the above intersection of oblique line and horizontal line
In the formula(5)
T0 is the precise lag of DBP.