Performance characteristics of the DeVilbiss Ultraneb 99 ultrasonic nebuliser with reference to use in sputum induction

Abstract

The DeVilbiss Ultraneb 99 ultrasonic nebuliser is frequently used for sputum induction in AIDS patients undergoing investigation of suspected Pneumocystis carinii pneumonia. We set out to characterise this machine under a wide range of operating conditions so that the efficiency of the technique might be optimised. The range and frequency of particle sizes remained reasonably constant and gave a Gaussian distribution pattern (mean MMD = 5.05 μm, SD = 0.34 μm) below a critical volume of nebulised solution, this volume being related to the intensity setting of the nebuliser. Beyond this volume, the particle size distribution adopted a bimodal pattern, and nebuliser output subsequently tailed off altogether. The volume of couplant within the nebuliser chamber was critical for efficient nebuliser output. Changes in surface tension and tonicity of solution to be nebulised did not affect the performance of the nebuliser substantially. Successful sputum induction may rely on both proximal and distal airway deposition, which may be enhanced by changes in both the nebuliser and nebulised solution.