Biomedical Engineering Reference
In-Depth Information
Fig. 10.59
Correlation between
FPM
<5.0μm
obtained from NGI and FSI reported by Sheng and
Watanabe from 0.5 mL aliquots of different nebulized budesonide preparations (Table
10.16
)
(
From
[
53
]—
courtesy of G. Sheng
)
that was operated with a 0.5 mL fill of a proprietary corticosteroid formulation in
aqueous suspension for inhalation.
Comparative measurements with an NGI (
n
= 6 replicates) and FSI (
n
= 5 repli-
cates) undertaken at both 28.3 L/min (Fig.
10.60
) and the preferred flow rate of
15 L/min for nebulizer testing (Fig.
10.61
) revealed similar values of
FPF
<5.0μm
, with
slightly less variability associated with the FSI data compared with the NGI at the
higher flow rate. However, it should be noted that neither the NGI nor the FSI were
chilled for this work, as their preliminary studies had shown this precaution to pre-
vent heat transfer-related evaporative loss with the aerosol droplets was not war-
ranted with the Aeroneb
®
Go system. Furthermore, Dennis et al
.
had shown in a
comparative study with the Aeroneb Go
®
and a jet nebulizer (MistyMax™, Cardinal
Health, USA) that bias in measures of MMAD, GSD, and fine droplet fraction from
not chilling the NGI were relatively small (<10% difference between measurements
made with this CI at room ambient and chilled to +5 °C) [
54
]. It is possible, there-
fore, that NGI chilling may only be needed for the most accurate measurement,
perhaps depending upon the formulation concerned [
55
,
56
], and the much lower
thermal mass of the FSI is likely to make this precaution even less necessary in
routine work.
However, droplet evaporation can be a significant concern when applying the CI
measurement technique to the measurement of aerosols produced by jet nebulizers,
especially those devices that do not entrain ambient air into the nebulized droplet
stream. The considerable heat capacity of the impactor, especially when the NGI is
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