Biomedical Engineering Reference
In-Depth Information
Fig. 8.18
Illustrative example for a healthy adult. (
Left
) the correlation function (time delay: 355
samples); (
right
) the mutual information (time delay: 350 samples)
Since we have a straight line in the log-log plot, from theoretical principles of frac-
tional calculus it follows that a power-law model can be fitted to each group of
patients [
126
], allowing deriving a model for each pathology:
C
F
d
=
A
ยท
(8.23)
with
A
and
B
identified constants.
8.3.2 Relations with Pathology
For each measured set of signals, we have extracted the breathing signal from the
pressure and flow signals by means of filtering. The volume was obtained by inte-
grating the flow and the pressure-volume loops were plotted for the entire signal
length.
From the breathing signal extracted from the pressure signal, the time delay value
T
d
was determined via the Pearson correlation function. For the sake of complete-
ness, the mutual information has also been calculated to check that similar time de-
lay values are obtained as with the correlation function (e.g. 355 and 350 samples,
respectively). An illustrative example for a healthy patient is given in Fig.
8.18
.
Next, based on the extracted time delay value, the PPP plot can be obtained. The
corresponding values for the time delay are given in Table
8.3
.
Figure
8.19
represents the evaluation of the obtained values for the time delay by
means of ANOVA tests (
p
was considered statistically significant for values lower
than 0.05). Statistically significant variations have been observed between the adult
groups (
p
0
.
001) and the children groups (
p<
0
.
0155). These delay values were
also verified against the biometric values of each group in order to determine if any
correlation was present. The corresponding trends are given in Fig.
8.20
for age.
Similar results were obtained for height and weight, respectively. The dependency
of the delay values with the biometric values has not been observed consistently in
all the evaluated groups.
