Biomedical Engineering Reference
In-Depth Information
vergence analysis reveals that this recurrent ladder network can be well approxi-
mated by a low-order lumped impedance model containing a FO, over a limited
range of frequencies. Similarly, we have shown that the mechanical analogue leads
also to a ladder structure, whose low-order lumped model also contains fractional
orders.
Therefore, a theoretical basis has been set onto which FO models arise. Fur-
thermore, the topic explains and provides supportive data to claim that FO lumped
impedance models are able to classify between healthy groups of subjects and sev-
eral pathologies: Chronic Obstructive Pulmonary Disease, asthma, cystic fibrosis
and kyphoscoliosis. Some typical indices from the literature, which were derived
from the identified model parameters, as well as several novel indices, are dis-
cussed for each of the groups in relation to the specific lung pathology. The results
show good agreement with physiology and pathology of the lungs in all investigated
groups.
Apart from the frequency domain, the topic contains also information about the
time domain signals. In this line of thought, the impulse response, pressure-volume
loops and multidimensional scaling tools are employed to analyze the breathing
dynamics and their relation to fractals.
The work presented in this topic provides a mathematical basis for the phe-
nomena observed in the results coming from the experimental data. We describe
a physiologically consistent approach to model the respiratory tree and show the
appearance of the fractional order impedance model and its typical constant-phase
characteristic. Rather than dealing with a specific case study, the modeling approach
presents a general method which can be applied in many other similar systems (e.g.
leaves, circulatory system, liver, intestines, brain). Although recurrence is linked
to symmetry of the tree, we consider also the case when symmetry is not present,
showing that the constant-phase behavior is still present, hence justifying once again
the use of fractional order models.
The overall aim of the work bundled in this topic is to provide a theoretical and
experimental basis of the information on the respiratory impedance extracted by
means of the forced oscillation technique lung function test. Although it has both
merit and simplicity, this lung function test is not a routinely used in clinical prac-
tice. I believe and I hope that this topic will provide the necessary proof of added
value necessary for taking the steps towards standardization.
Apart from this, a major goal of this topic is to bring forward the existence of
several emerging tools from fractional calculus in the biomedical engineering com-
munity. Although the content of the topic is not focusing on the concepts of frac-
tional calculus, it provides a mere introduction which suffices to assist the reader in
this quest. The growing interest coming from the engineering community into these
emerging tools motivates all researchers at large to stay abreast latest applications.
On the other hand, biologists and doctors are encouraged to embrace these concepts
in order to achieve progress in their endeavor to understand the human body and its
features.
