Biomedical Engineering Reference
In-Depth Information
Fig. 6.4
A schematic representation of the electrical model for the lung parenchymal tissue as an
interconnected system (starting from level 16)
study, we investigate the airways within the respiratory zone, corresponding to levels
16-24, as schematically depicted in Fig.
6.4
[
66
,
164
]. In this figure,
A
m
denotes
the cross-sectional area,
m
denotes the length,
R
em
the resistance, and
C
em
the
capacitance of one airway tube from level
m
, respectively.
In the respiratory zone, the oxygen and carbon dioxide exchange takes place
between the air in the lung and the blood in the small-diameter blood vessels that
surround the alveoli. The gas compression impedance is modeled by a
R
GC
−
L
GC
−
C
GC
series impedance, as described in Chap.
5
.
For the case of elastic tube walls, we have no viscous losses, thus no conductance
G
e
element, as defined in Sect.
4.2.1
.Using(
4.62
)-(
4.64
), the equations for the
electrical model are given by
R
e
2
2
e
0
=
R
e
1
i
1
+
e
1
;
e
1
=
i
2
+
e
2
(6.9)
i
1
=
i
2
+
C
e
1
˙
e
1
;
i
2
=
2
C
e
2
˙
e
2
with
e
the voltage and
i
the current represented as in Fig.
6.5
. The electro-
mechanical analogy is given in Table
6.1
.
Using the electro-mechanical analogy from Table
6.1
, we can derive an equiva-
lent mechanical model. This can be done starting from the electrical model equa-
tions (
6.9
). The electrical element (
R
e
C
e
series) corresponds to the mechanical
Kelvin-Voigt element (spring in parallel with dashpot):
