A systematic review of the clinical effectiveness of dry powder inhalers in the treatment of acute exacerbations of asthma in adults and children, and in the maintenance treatment of asthma in children

Problem

Metered dose inhalers (MDIs) account for 3% of the total NHS carbon emissions each year due to their use of hydrofluorocarbon propellants, which are highly potent greenhouse gases. The NHS has pledged to be carbon net-zero by 2040 and reducing prescribing of MDIs is crucial in achieving that goal. Dry powder inhalers (DPIs) are an alternative type of inhaler with a much lower carbon footprint and this type of inhaler is equally efficacious for most adults with asthma. However, there is uncertainty about the efficacy and safety of DPIs for young children or during acute asthma exacerbations.   This systematic review aims to assess the clinical effectiveness of dry powder inhalers in two clinical contexts: 1) The treatment of acute exacerbations of asthma in adults and children 2) Maintenance treatment of asthma in children.

Approach

This systematic review was carried out in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and has been registered with PROSPERO (CRD42022368492). A systematic search of six medical databases was carried out on the 17th October 2022. Inclusion criteria were: primary studies involving participants with a diagnosis of asthma who had been treated using a DPI either during an acute exacerbation, or for maintenance therapy if they were <18 years old. Studies published in any language and country were included and there were no restrictions based on publication date. The main outcomes of interest were those pertaining to resolution of acute exacerbations or measures of asthma control for studies of maintenance therapy. Titles were screened by one member of the team and abstract and full-text screening were carried out independently by two reviewers, with conflicts resolved by a third reviewer. Data extraction was checked by a second member of the review team. Risk of bias of included studies was assessed using ROBINS I, Cochrane Risk of Bias Tool and appropriate CASP tools. Results were narratively synthesised.

Findings

15 studies were included in the acute asthma category; 7 in children only and 8 in adolescents and adults. Sample size ranged from 20-216 and all were published prior to 2011. Results from studies of DPI use in acute asthma suggest that that there is clinical equivalence between treatment with DPIs and other inhalers in both children and adults. However, the majority of studies had high risk of bias and the quality of the overall evidence base was low. Synthesis of results from studies of maintenance treatment of asthma in children is underway.

Consequences

This systematic review has the potential to inform guidelines for inhaler prescribing by providing an up-to-date evidence summary on the use of DPIs in specific clinical contexts. This work may also highlight gaps in the evidence base and areas for future research.