INVITED ABSTRACT
Laser Diffraction Measurement of Droplet Sizes Generated by Vibrating Mesh Nebulization in Air and a Helium-Oxygen Mixture

AR Martin (1), J Gleske (2), IM Katz (1,3), M Hartmann (2), B Mullinger (2), S Haussermann (1), G Caillibotte (1), G Scheuch (2)

(1) Medical Gases Group, Air Liquide R&D CRCD, Les Loges-en-Josas, France (2) Activaero GmbH, Gauting, Germany (3) Department of Mechanical Engineering, Lafayette College, Easton, PA, USA

     Abstract Number: 485
     Last modified: May 13, 2010

Abstract
Inhalation of helium-oxygen gas mixtures has been widely explored as an interim therapy intended to reduce airway resistance and work of breathing in patients with obstructed airways. Recent clinical studies support the use of helium-oxygen to treat acute exacerbations of asthma and COPD. In these applications, helium-oxygen may be delivered in combination with aerosolized bronchodilator, thus it is of interest to assess the effects of gas properties on the characteristics of the administered aerosol. Similarly, where helium-oxygen has been advocated as a carrier gas to better transport medical aerosols into the lung, it is important to distinguish between effects of gas properties on aerosol generation and on fluid and particle mechanics influencing deposition patterns in the respiratory tract.

This work investigated the influence of the supplied gas, either air or a mixture containing 78% helium and 22% oxygen, on droplet sizes produced by a high output rate nebulizer incorporated in combined gas-aerosol delivery systems (AKITA2 and AKITA2 Oxhel; Activaero GmbH, Gauting, Germany) using vibrating mesh technology (Touch Spray Technology, Pari Pharma GmbH). Droplet size distributions were measured by laser diffraction. Nebulization was performed using three different meshes, producing droplets with nominal volume median diameters (VMDs) of 3, 4, or 5 micro-meters. Measured VMDs were stable, in that they were in all cases within ± 10% of their nominal values, and unaffected by humidity or dilution of the aerosol stream. While VMDs were consistently 5-10% smaller in helium-oxygen than in air, this variation was small compared to variation between meshes. Accordingly, use of high output rate vibrating mesh nebulizers, such as that tested, allows consistent control of delivered droplet sizes in helium-oxygen and air.