Some factors influencing the efficiency of a jet nebuliser system

Abstract

The operation of a commercially available nebuliser system (Medic-Aid Ltd) is reviewed and the efficiency with which it produces an aerosol assessed. Defining the efficiency of nebulisation E as the fraction of the original mass of solution released as an aerosol it is found that the internal surface area, mass of solution used, the surface tension of the solution and the angle of tilt are important factors in determining E. Reducing the internal surface area of the nebuliser by means of Perspex inserts significantly increases E for 3 g of water from 49% for the unmodified system to 67% for the modified nebuliser (P less than 0.01). E increases with the mass of solution used but only exceeds 60% when 4.5 g water are used. Decreasing the surface tension of the solution from 7.2 x 10(-3) N m-1 (water) to 3.7 x 10(-3) N m-1 and 3.1 x 10(-3) N m-1 (using two different concentrations of a detergent in water) significantly increases E for 3 g solution from 49% to 65% and 69% respectively (P less than 0.05). Operating the nebuliser at a tilt also increases E. The measurements emphasise the importance of reducing the internal surface area of this type of nebuliser, using an adequate volume of drug solution (at least 4 ml is suggested) and operating the nebuliser at an angle to the vertical (20 degrees suggested) in order to maximise E. The surface tension of the drug solution is a further important determinant of E.

Nebulisers for the generation of liposomal aerosols

“…Larger droplets are therefore retained within the nebuliser, and as a result the effects of viscosity and surface tension are masked (Newman et al, 1987). This is supported by the fact that a decrease in aerosol output rate is a well documented consequence of nebulising fluids with increased surface tensions (Davis et al, 1978;Clay et al, 1983b: Smye et al, 1990, and also viscosities (McCallion and Patel, 1996).…”

A new method for measuring aerosol nebulizer output using radioactive tracers

“…We confirm the findings of DENNIS et al [2], who used a chemical tracer to measure actual aerosol output. The discrepancy between weight loss and direct measurement of aerosol has also previously been shown by SMYE and coworkers [5,6]. O'CALLAGHAN et al [7] used a spectrophotometric method to assess drug output from nebulizers, but this method requires specialized equipment and may not be sensitive enough for smaller dosimeter doses.…”