Objective: To compare the effect of bronchodilator delivery by use of a metered-dose inhaler (MDI) or wet nebulizer on objective measurements of acute airflow obstruction in adult patients.
Methods: Published and unpublished research was identified by MEDLINE searches for articles published from 1966 to 1994, review of scientific citations, review of article bibliographies, communication with experts in the area of asthma therapy and aerosol delivery, primary investigators, and a manufacturer of spacer devices. Eighteen studies were selected from 159 potentially relevant articles by independent review in triplicate. Selection criteria included randomized trials that compared bronchodilator delivery by use of an MDI and wet nebulizer in adults with acute exacerbations of asthma or chronic obstructive pulmonary disease who were treated in an emergency department or a hospital. Data for patient characteristics, study setting, bronchodilator doses, outcomes, and methodological quality were independently extracted.
Results: Twelve studies with a total of 507 patients had sufficient data to calculate an effect size (in SD units) for improvement in airflow obstruction after bronchodilator delivery. All but 2 studies used spacer devices with the MDI. The overall treatment effect size was -0.02 (95% confidence interval [CI], -0.20 to 0.16) that favored the MDI, but the magnitude of the effect size was not clinically or statistically significant. No significant effect was observed in the subgroup analyses that compared the diagnosis: asthma, -0.17 (CI, -0.41 to 0.07) compared with chronic obstructive pulmonary disease, 0.23 (CI, -0.35 to 0.81); bronchodilator dose; or methodological quality. The results of a sensitivity analysis that included 5 of 6 excluded studies supported the findings from the primary analysis: 0.05 (CI, -0.11 to 0.20).
Conclusions: Bronchodilator delivery by means of an MDI or wet nebulizer is equivalent in the acute treatment of adults with airflow obstruction. Spacer devices were used for bronchodilator delivery with an MDI in most studies and are recommended for the treatment of acute airflow obstruction. The choice of the delivery method will depend on the need for expedient treatment, availability of staff, consideration of costs, and findings from studies designed to evaluate treatment effects from larger than standard doses of bronchodilators delivered by use of an MDI.