Biomedical Engineering Reference
In-Depth Information
Fig. 3.1
Regional deposition of particles in the adult respiratory tract, based on the ICRP human
respiratory tract model for radiological protection (
From
[
15
]—
used with permission
)
0.5 to 15
m. In the case of an oral tidal-breathing adult, particles with
d
ae
larger
than approximately 5
μ
m deposit mainly in the oropharyngeal region, central (bron-
chial) airway deposition peaks with particles with
d
ae
between 7 and 9
μ
m, and
peripheral (alveolar) deposition in the lung reaches a maximum with particles hav-
ing
d
ae
between 2 and 4
μ
m (Fig.
3.2
). Particle aerodynamic size is therefore a sensi-
tive measure of likely HRT deposition location. This fact has formed the basis of
several attempts to develop either mathematically rigorous in vitro-in vivo correla-
tions (IVIVCs) or somewhat less predictive relationships (IVIVRs) from the stand-
point of proportionality, thus far with limited success [
16
]. This situation is due to a
variety of reasons, not least the relative insensitivity of clinical metrics based on
lung mechanics to the action of APIs whose purpose and function are other than
dilatation of the airways (e.g., inhaled corticosteroids that are used to reduce under-
lying inflammatory disease).
In summary, the creation and delivery of an aerosol containing micron-sized
particles by any of the OIP forms mentioned previously is favorable for the efficient
delivery of medication past the oropharynx (upper respiratory tract) to the airways
of the lungs where the receptors are located for the treatment of the various diseases
associated with this organ, commonly but not restricted to asthma, COPD, and
μ
Search WWH ::
Custom Search