EVIDENCE-BASED ANSWER
Metered-dose inhalers with a spacer (MDI/S) are as good as, or better than, nebulizers for children with asthma. This is based on numerous randomized controlled trials that compared outcomes such as hospital admission rates, asthma severity scores, and pulmonary function scores (strength of recommendation: A, based on consistent randomized controlled trials and meta-analysis).
Evidence summary
A Cochrane review of 10 randomized controlled trials comparing nebulizers with MDI/S, both in adults and in children aged >2 years, showed a substantial trend towards improvement in hospital admission rates with MDI/S use. Sample size for each study was small, ranging from 18 to 152 patients, with a total sample size of 880 children and 444 adults.
The relative risk of admission for MDI/S vs nebulizer for children was 0.65 (95% confidence interval, 0.4–1.06). Secondary outcomes were equivalent or slightly improved, including duration in the emergency department, changes in respiratory rate, blood gases, pulse, tremor, symptoms score, lung function, and use of steroids. Patients with life-threatening asthma (for example, those considered for ventilation) or other chronic illnesses were excluded.1
All but 1 of these studies were set in the emergency department and all involved the use of one of a variety of spacers with the MDI, such as the Aerochamber or Inspirease. Whether these efficacy studies can be translated into daily outpatient clinical practice remains unclear. Emergency departments typically have higher staffing levels, and study subjects and their parents may have received more MDI/S training than is practical in many office settings.
While most of the data were for children aged 2 years and older, 1 study published after the Cochrane review did show a lower admission rate in 85 patients who were 2 to 24 months in the MDI/S group.2 Controlling for the initial Pulmonary Index score, children using an MDI and Aerochamber spacer were admitted less often (5% vs 20%, number needed to treat=7; P=.05) than children using nebulizers. Since the results of this single small trial are the only data available for this younger age group, using MDI/S instead of nebulizers should be done with caution for children aged <2 years.
Another randomized controlled trial of 152 patients found no difference in primary outcomes of asthma severity score, oxygen saturation, and percent predicted peak expiratory flow rate (PEFR). Several secondary outcomes slightly favored MDI/S: number of treatments given, whether steroids were used, change in heart rate, side effects, rate of hospital admission, and treatment time in the emergency department.3
A smaller double-blinded randomized controlled trial of 33 children aged 6 to 14 years showed no difference in MDI/S vs nebulizer, as measured by clinical score, respiratory rate, oxygen saturation, and forced expiratory volume at 1 second (FEV1).4 The researchers calculated the study had 90% power to detect a clinically meaningful difference in FEV1 of 12% of the predicted value between the groups.