Biomedical Engineering Reference
In-Depth Information
EXAMPLE PROBLEM 9.2
Electric safety is of paramount importance in a hospital or clinical environment. If sufficient
current is allowed to flow through the body, significant damage can occur, as illustrated in the
following figure.
Burns, Injury
Sustained Myocardial
Contraction
Ventricular Fibrillation
Respiratory Paralysis, Fatigue, Pain
Let-go
Current
Threshold of
Perception
0.0001
0.001
0.01
0.1
1.0
10.0
100.0
Current (A)
For instance, a current of magnitude 50 mA (dashed line) is enough to cause ventricular fibrilla-
tion, as well as other conditions. The figure on the left shows the current distribution from a macro-
shock from one arm to another. A crude electric circuit model of the body consisting of two arms
(each with resistance
R
A)
, two legs (each with resistance
R
L
), body trunk (with resistance
R
T
), and
head (with resistance
R
H
) is shown in the following figure on the right.
R
H
R
A
R
A
+
R
T
−
R
L
R
L
V
S
Continued
