SELECTED ARTICLES FROM THE RECENT LITERATURE 2005

11/7/05

Nebulizer performance under various humidity conditions

Summary
Background - Jet nebulizers ( Neb ) are commonly used to deliver inhaled asthma medications to the lower airways, particularly in young children. When Neb generate aerosols, the rate which the aerosol droplets evaporate, and secondarily the aerosolized drug delivery, is affected by the ambient relative humidity (RH) around the Neb output port.

Findings - Zhou et al of the Loveland Research Institute in Albuquerque, NM compared the delivery of 2 types of aerosols (albuterol solution, budesonide suspension) by 4 different neb devices at various RH conditions (5-50%). In general, the mean droplet diameters increased and drug delivery to the airways decreased with increasing RH. Also, the respirable fraction (equivalent to inhalation dose) was lower at higher RH. The authors concluded that the efficacy of various Neb to deliver aerosol medications decreased progressively as the local RH increases.

Reference
J Aerosol Med 2005;18:283-295

Editor's Comments
Like most clinicians, I am not that knowledgeable about technical aspects of aerosol formation and evaporation. However, we should all recognize that our assumption of inhaled drug delivery depends on such technical aspects, including effects of RH and possibly other atmospheric conditions.

 

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