Biomedical Engineering Reference
In-Depth Information
carbon dioxide (P CO 2 ) in the respiratory system or blood are often measured to evaluate
normal levels of blood oxygen concentration. All of these constitute biochemical signals.
These biochemical signals can be used for a variety of purposes, such as determining levels
of glucose, lactate, and metabolites and providing information about the function of various
physiological systems.
11.2.4 Biomechanical Signals
Mechanical functions of biological systems, which include motion, displacement, tension,
force, pressure, and flow, also produce measurable biological signals. Blood pressure, for
example, is a measurement of the force that blood exerts against the walls of blood vessels.
Changes in blood pressure can be recorded as a waveform (Figure 11.2). The upstrokes in the
waveform represent the contraction of the ventricles of the heart as blood is ejected from the
heart into the body and blood pressure increases to the systolic pressure, the maximum blood
pressure (see Chapter 3). The downward portion of the waveform depicts ventricular relaxa-
tion as the blood pressure drops to the minimum value, better known as the diastolic pressure.
AORTIC PRESSURE (mmHG)
100
90
80
70
60
50
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
TIME (secs)
FIGURE 11.2
Blood pressure waveform recorded from the aortic arch of a 4-year-old child. (Sampled at
200 samples/s.)
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