2004 OPEN FORUM Abstracts
VARIABILITY OF THE PARTICLE SIZE DISTRIBUTIONS FROM NEBULIZERS POWERED WITH OXYGEN OR HELIOX.
Stephan
Gamard, Ph.D., Healthcare R&D, Praxair Inc., Tonawanda, NY;
Timothy E. Corcoran, Ph.D., Division of Pulmonary, Allergy, and
critical Care Medicine, University of Pittsburgh, Pittsburgh, PA.
Background: Heliox (mixture of helium and oxygen) is sometimes
used to power
medical nebulizers. Since the particle size distribution of an
aerosol might affect the drug deposition rate in the pulmonary tract,
we decided to investigate its dependence on different gas composition
and flow rates along with its consistency between nebulizers of the
same brand and manufacturer.
Method: Three commercially available nebulizers brands were
chosen:
Misty-Neb™ (Allegiance Healthcare Corp., McGaw Park,
IL), Heart® (Westmed, Tucson, AZ), and Hope Nebulizer™
(B&B Medical Tech. Inc., Loomis, CA) and filled with isotonic
saline water. A Malvern Mastersizer S laser diffraction particle size
analyzer was used to obtain the particle size distributions. Three
devices for each nebulizer brand were used for testing in order to
quantify the eventual variation for each product within the same
nebulizer brand. Each device arrived sealed and ordered by normal
buying channels. Gas was flown at 50 psig in three different
concentrations: 100% Oxygen (0/100), 50% Helium/50% Oxygen (50/50),
80% Helium/20% Oxygen (80/20). Flow rate was varied from 5 L/min to
27 L/min depending on the gas composition.
Results: Overall, the Dv[50] (volume median diameter) varied
significantly
with flow rate, gas composition, and devices within a given nebulizer
brand. Increases in flow rate or oxygen concentration tended to
decrease the aerosol size. Multiple regression analyses based on
minimizing the pooled estimates of the standard deviations were used
to try to capture the behavior of the Dv[50]. Different models were
tried accounting for linear or higher order dependence on the
variables, while still pooling all the data simultaneously.
Surprisingly, for each nebulizer brand tested (Misty-Neb™,
Heart®, and Hope™), the variation
between devices within the same brand was so important that no
overall model for the brand could be found (see Table 1).
Conclusion:These particle size tests show that the aerosol properties are highly
dependent not only on flow rate and gas composition, but also can
significantly vary from one device to the other for the same
nebulizer brand. This might eventually affect the overall drug
deposition within the respiratory tract. We suggest that
investigations including gas-powered medical nebulizers verify the
particle size distribution in order to ensure equivalency between
tests. This is particularly relevant in studies involving heliox when
the gas density affects the aerosol size.
Table
1: Regression model of the experimental testing.
Dv[50]=Do + Ao
(Oxygen %)/100 + Aq (flow rate).
| Brand | Misty-Neb™ | Hope™ | Heart® | ||||||
| Device | N#1 | N#2 | N#3 | N#1 | N#2 | N#3 | N#1 | N#2 | N#3 |
| Do | 7.10 | 8.06 | 9.31 | 8.80 | 9.78 | 10.62 | 8.89 | 13.41 | 11.11 |
| Ao | -0.0456 | -0.773 | -1.86 | -2.01 | -1.98 | -3.11 | -1.42 | -3.72 | -1.56 |
| Aq | -0.275 | -0.309 | -0.320 | -0.107 | -0.163 | -0.201 | -0.214 | -0.365 | -0.392 |