Biomedical Engineering Reference
In-Depth Information
Ta b l e 5 . 3
Biometric
parameters of the investigated
subjects in the mid-frequency
range (4-48 Hz) and in the
low frequency range
(0.9-5.3 Hz); values are
presented as mean
±
standard
deviation
4-48 Hz
0.9-5.3 Hz
male (15)
female (8)
male (8)
female (2)
±
±
±
±
Age (yrs)
23
0
.
7 3
1
.
3
.
2
2
.
1
.
5
2
.
1
Height (m)
1
.
76
±
0
.
06
1
.
68
±
0
.
03
1
.
75
±
0
.
07
1
.
72
±
0
.
02
Weight (kg)
73
±
5
.
1 3
±
2
.
8
.
1
±
7
.
11
66
.
5
±
10
.
6
Fig. 5.14
Measured impedance values from healthy subjects (
left
) and the corresponding mean
with standard deviation values (
right
)
5.3.2 A Study on Measured Respiratory Impedance
In order to validate this ladder network model, respiratory impedance has been es-
timated using non-parametric methods described in Chap.
2
and in (
3.8
)intwodif-
ferent frequency intervals: (i) mid-range frequencies between 4-50 Hz and (ii) low-
range frequencies between 0.9-5.3 Hz. The impedance over the mid-frequency
range interval has been acquired using the standard FOT device described previ-
ously. Since a loudspeaker has limitations at low frequencies, a prototype mechani-
cal device has been used to measure impedance over the low frequency range.
The measured frequency interval used in standard clinical tests is 4-48 Hz, re-
spectively, 25-300 rad/s. Previously available records from 23 healthy volunteers
have been used to support the validity of the model with morphological values [
72
],
and their biometric values are given in Table
5.3
. An additional set of 10 healthy vol-
unteers whose biometric values are given in the same table are measured with low
frequency FOT, for the 0.9-5.3 Hz frequency interval. The impedance data from the
healthy subjects with the corresponding mean and standard deviation values is given
in Fig.
5.14
.
From the measured healthy subjects, we obtain the averaged impedance and
the standard deviation values which offer a lower and upper bound, as depicted
in Fig.
5.14
. The RLC-ladder model for the respiratory tree calculated with param-
eters from Table
2.1
and (
4.62
)-(
4.64
) neglects the impedance introduced by the
upper airways segment. In order to make the comparison with the measured data,
