Biomedical Engineering Reference
In-Depth Information
a
b
Fig. 1.8
Particle trajectories shown by the
coloured lines
and deposition sites shown by
dots
for
a
50 μm particles at a horizontal insertion and
b
10 μm particles at vertical insertion. (From
Inthavong et al. 2006b)
blood returning back to the heart) from the nose passes directly into the systemic
circulation leading to a rapid onset of action from the initial drug absorption. This
has further advantages, including avoiding loss of drug by first-pass metabolism in
the liver, fewer side effects, painless compared to injections, and the drug may even
be delivered directly to the brain along the olfactory nerves (Oberdörster et al. 2004).
Similar to lung airways, the physiological function of the nose is for respira-
tion as well as olfaction. The nose's unique geometry has defence mechanisms to
prevent foreign particles from entering into the main nasal passage. Experimental
studies have found that particle deposition from nasal sprays primarily occurs in the
anterior third (up to the nasal valve region) of the nasal cavity (Cheng et al. 2001;
Newman et al. 1998). CFPD research can be used in conjunction with experiments
to better understand the particle dynamics and final deposition in the nasal cavity.
As an example, we present the particle trajectories and deposition sites for 50 and
10
m particles released inside the nasal cavity at different directions that may be
achieved by the nasal spray design. The visualisation in Fig.
1.8
shows that a hor-
izontal insertion angle (90
◦
) for 50
μ
μ
m provides later deposition at the back of the
nasopharyngeal region. Although 10
m particles deposit more readily in the middle
turbinate regions of the nasal cavity, their transport beyond the nasopharynx leads to
undesirable deposition in the lungs.
The fate of each particle released from specific points was achieved by individually
tracking the particle's trajectory through the nasal cavity. The deposition patterns
μ
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