220
Dynamics
of
the Vascular System
pressure, obtained from static calibrations. This is not generally a
problem, since most combinations have static calibrations that are linear
to within
f
1
%
or better, over the range of
0-200
mmHg. Hysteresis refers
to
the differences in outputs with increasing and decreasing blood
pressure within the blood pressure range of interest.
This is also
typically small.
Thus, dynamic frequency response is of the major
importance.
Fig.
8.1.3:
frequency. The resonance frequency in this example is
20
Hz.
Dynamic frequency response shown as the relative amplitude ratio vs.
Blood pressure waveforms that are closer to sinusoidal waveforms
require less harmonic components to resynthesize the original waveform
and thus place less stringent demand on the frequency response.
For
instance, the femoral artery can be recorded with a lower dynamic
frequency response than either central aortic pressure of left ventricular
pressure.
This is because the femoral arterial pressure is generally
smoother and with rounded dicrotic notch. Blood pressure waveforms
that are closer
to
rectangular waveform require much higher frequency
response to resynthesize the waveforms accurately. This is because
rectangular and square waves contain an infinite number of sinusoidal or
cosinusoidal components. Normal left ventricular pressure, for instance
