Variability in Jet Nebulizer Output

Abstract

To the Editor: We read with interest in the February 1992 issue of Chest the article by Alvine and colleagues1Alvine GF Rodgers P Fitzsimmons KM Ahrens RC Disposable jet nebulizers: how reliable are they?.Chest. 1992; 101: 316-319Abstract Full Text Full Text PDF PubMed Scopus (118) Google Scholar on the reliability of jet nebulizers. The authors discuss in detail the differences in fluid output and particle size between different jet nebulizers and the potential effects on clinical response. Unfortunately, they fail to consider the crucial aspect of drug output, assuming as others have done, that it follows fluid output,2Steventon RD Wilson RSE Nebulizer units.Br J Clin Equip. 1979; (July): 153-156Google Scholar, 3Clay MM Pavia D Newman SP Lennard-Jones T Clarke SW Assessment of jet nebulizers for lung aerosol therapy.Lancet. 1983; 2: 592-594Abstract PubMed Scopus (139) Google Scholar an incorrect assumption for salbutamol,4Wood JA Wilson RSE Bray C Changes in salbutamol concentrations in the reservoir solution of a jet nebulizer.Br J Dis Chest. 1986; 80: 164-169Abstract Full Text PDF PubMed Scopus (34) Google Scholar, 5Langford S, Allen MB. Salbutamol output from two jet nebulizers. Respir Med (in press)Google Scholar antibiotics,6Newman SP Pellow PGD Clay MM Clarke SW Evaluation of jet nebulizers for use with gentamicin solution.Thorax. 1985; 40: 671-676Crossref PubMed Scopus (107) Google Scholar and sodium cromoglycate.7O'Callaghan C Clarke AR Milner AD Inaccurate calculation of drug output from nebulizers.Eur J Paediatr. 1989; 148: 473-474Crossref PubMed Scopus (34) Google Scholar This variability in both fluid and drug outputs is of concern to clinicians.8Langford S Allen MB Variation in drug delivery with nebulizers: effect of type and batch [abstract].Eur Respir J. 1990; 3: 54Google Scholar Of greater importance would be any variations in output between nebulizer units from the same manufacturer. We have examined this by measuring both fluid and drug output from four nebulizers with the same batch number from one manufacturer (System 22, Medic-Aid, Chichester, England). A single nebulizer was weighed before and after the introduction of 2 ml of 50:50 normal saline-salbutamol solution (Ventolin Respirator solution containing salbutamol sulfate, 5 mg/ml, Allen & Hanburys). The nebulizer was then run for a predetermined period using air from an electric compressor at a verified flow of 9 L/min. The unit was weighed again after nebulization to give the fluid output (corrected for weight of the salbutamol respirator solution). Five 100-μ1 aliquots were taken from the solution remaining within the nebulizer unit for analysis of salbutamol by ultraviolet spectrophotometry (SP400 UV/VIS spectrophotometer, Pye Unicam, Cambridge, England). From the absorbance at 225 nm, the concentration of salbutamol was calculated by reference to a standard calibration curve constructed using analytical-grade salbutamol sulfate. With knowledge of the initial concentration and weight change, the salbutamol output at each time interval could be calculated. The nebulizer unit was then carefully washed and dried before the procedure was repeated for a different time period. Runs were performed at 1-min intervals up to 10 min for each of the 4 nebulizer units. Figure 1 shows the salbutamol output of each unit. There was a greater output of fluid than salbutamol, which led to small increases in the salbutamol concentration within the nebulizer. Fluid and salbutamol outputs were reasonable but less than ideal9Kradjan WA Lakshminarayan S Efficiency of air compressor-driven nebulizers.Chest. 1985; 87: 512-516Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar for units C and D. Unit A was more variable in its output, although the 10-min results were similar to those achieved with units C and D. The fluid and drug outputs from unit B were poor, with less than 20 percent of the salbutamol being delivered after 10 min. Although differences in fluid output are recognized between manufacturers, the results we have obtained illustrate the variation in drug output that may occur between nebulizer units from the same batch. The peak salbutamol output occurred at 10 min and ranged from 18.3 percent to 54.1 percent of the initial 5-mg fill. If medical practitioners are to prescribe high doses of bronchodilators, it must be with the knowledge that this is what the patient receives; for some nebulizer units this is clearly not so. The onus of providing this information must be placed with the manufacturers.