Fukuda VaSera VS-2000 Series, Operation Manual

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13-3
Chapter 13 Appendix
The actual CAVI is coordinate-transformed to correspond to aortic PWV.
Brachial blood pressure is used as the average systolic pressure (Ps) and diastolic pressure (Pd) of the body.
(4) PWV (Pulse Wave Velocity)
Pulse wave traveling through the blood vessels is recorded at two blood vessel locations. Then by dividing the distance
between the two locations with the pulse wave time difference between the two locations produces PWV, a speed value
and an index that assesses the stiffness of the arteries. The higher the PWV, the stiffer the arterial wall is.
L: Distance between two blood vessel locations,
Δ
T: Pulse wave time difference between the two blood vessel
locations
The following two PWV are used to calculate CAVI.
• Heart valve - right (left) ankle artery PWV
(5) Time measurement of pulse waves
To calculate PWV, we need to obtain pulse transmission time T from the
heart valve to the ankle.
To establish T = t'b + tba
t'b = tb,
T = tb + tba is obtained.
• First heart sound: Includes the opening snap of the aortic valve
• Second heart sound: Closing snap of the aortic valve
• Notch of the brachial pulse wave: Pulse wave at the closing the aortic
valve
• t'b: Time between the first heart sound and the rise of the brachial
pulse wave
• tb: Time between precomponents of the second heart sound and the
notch of the brachial pulse wave
• tba: Time difference between the rise of the brachial pulse wave and
that of ankle pulse wave
b
2
ln a
2
+
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
⋅
⎟
⎠
⎞
⎜
⎝
⎛
⋅ =
Pd Ps
PWV
Pd
Ps
CAVI
Ȩ࣭
(a, b: Conversion Constant)
ECG
PCG
Brachial
PWV
Ankle
PWV