Biomedical Engineering Reference
In-Depth Information
Ta b l e 3 . 1
Biometric and
spirometric parameters of the
investigated (male) subjects.
Values are presented as
mean
±
SD; % pred:
predicted according to the
asymptomatic males of the
present study; VC: vital
capacity; FEV1: forced
expiratory volume in 1 s
Healthy
(7)
Asthma
(5)
COPD
(14)
±
±
±
Age (yrs)
55
3
65
2
51
6
Height (m)
1
.
74
±
0
.
15
1
.
62
±
0
.
12
1
.
73
±
0
.
14
Weight (kg)
82
±
4
78
±
5
71
±
5
VC % pred
100
±
3
80
±
8
89
±
7
FEV1 % pred
100
±
4
53
±
7
44
±
6
and
P(s)
Q(s)
=
R
r
+
L
r
s
α
r
1
C
r
s
β
r
Z
r
(s)
=
+
(3.10)
with
P
pressure in cmH
2
O;
Q
flow in l/s;
Z
r
the impedance in cmH
2
O/(l/s);
R
r
air-
way resistance in cmH
2
O/(l/s),
L
r
inductance in cmH
2
O/(l/s
2
);
C
r
capacitance in
l/cmH
2
O; 0
1 fractional orders and
s
the Laplace operator.
Using the definition of complex numbers, (
3.10
) becomes
≤
α
r
≤
1 and 0
≤
β
r
≤
L
r
ω
α
r
cos
α
r
π
2
cos
β
r
π
2
1
C
r
ω
β
r
Z
r
(j ω)
=
R
r
+
+
L
r
ω
α
r
sin
α
r
π
2
sin
β
r
π
2
1
C
r
ω
β
r
+
j
·
−
(3.11)
It is possible to see that, contrary to a RLC series system, the real part of the
impedance in (
3.11
) will vary with frequency and comprises both inductance and
compliance effects. Therefore, it allows to characterize both increase and decrease
with frequency in the real part of impedance, without requiring a high integer-order
system.
3.3.2 The Volunteers
In this chapter, we are dealing with subjects evaluated with the classical FOT non-
invasive lung function test. There are three (averaged) data sets from groups of Cau-
casian healthy, asthmatic and COPD patients. Table
3.1
presents the corresponding
biometric and spirometric details.
The choice of these representative cases is motivated by the general aim of the
study: to evaluate the parametric models on the input impedance of these three sets
of subjects. The physiological differences between these sets of subjects are clearly
visible in the complex impedance values and we expect that the parametric models
proposed in this section will be able to quantify their specific properties.
