CLINICAL QUESTION: Which types of homemade spacers are most effective for inhaled b-agonist delivery in children with acute asthma exacerbations?
BACKGROUND: Multiple studies have demonstrated that for acute asthma exacerbations, metered dose inhalers (MDIs) with attached valved spacers are as effective, if not more effective, than nebulizers. Homemade spacers made from more readily available plastic bottles or polystyrene cups are sometimes substituted for conventional spacers. This study compares clinical outcomes using conventional spacers with 3 types of homemade spacers in children with acute asthma exacerbations.
POPULATION STUDIED: A total of 88 children aged 5 to 13 years who were experiencing an acute asthma attack were recruited from a Cape Town, South Africa, hospital emergency department. All subjects had a baseline peak expiratory flow rate (PEFR) between 20% and 80% predicted. The children were stratified by severity, with a PEFR of higher than 59% considered mild and a rate lower than 60% considered moderate. Patients who had used b-agonist medication within 4 hours of presentation were excluded.
STUDY DESIGN AND VALIDITY: This was a randomized trial comparing 4 spacer options: conventional valved spacers, plastic drink bottles sealed to the MDI with glue, plastic drink bottles that were not sealed, and polystyrene cups. To make the spacers, a heated wire in the shape of the MDI mouthpiece was pressed to the base of the bottle or cup to make a hole into which the MDI was inserted. Pulmonary function tests (PFTs) were performed at baseline and again after treatment with a b-agonist delivered by MDI and the assigned spacer type. Those patients who did not improve to at least 70% of predicted PEFR were given a nebulizer treatment with the same medication. Those nonresponders had a third set of PFTs after the nebulizer treatment. The investigators who evaluated outcomes were blinded to the treatment arm.
OUTCOMES MEASURED: The authors list 4 primary outcomes: change in a clinical asthma severity score, percent change in PFTs, failure to increase PEFR to higher than 70% of predicted, and change in PEFR with nebulizer treatment in nonresponders.
RESULTS: The pooled analysis, combining the mild and moderate groups, showed significant differences by spacer type for change in PFTs. For this combined group, the polystyrene cup resulted in minimal improvement in PFTs, while the other 3 spacer types showed significantly larger increases. When the mild severity group was analyzed separately, there were no significant differences by spacer type in any of the outcomes. For the moderate severity group, significant differences were found in change in PFTs, number of responders, and response to nebulizer for initial nonresponders. In all significant results in this moderate group, the conventional spacer performed the best and the polystyrene cup the worst, with the unsealed bottle somewhat more effective than the cup but less effective than the sealed bottle.
Delivery of b-agonist medication to patients with asthma attacks can be most effectively accomplished with an MDI combined with a conventional valved spacer. If conventional spacers are not available, a homemade spacer can be made from a 500-mL plastic drink bottle. A tight seal between the MDI and the bottle seems to increase the efficiency of medication delivery. For patients with moderate asthma symptoms, spacers made out of polystyrene cups are much less effective than spacers made out of plastic bottles or conventional spacers.