Risk of small-volume nebulizer treatments in the transmission of bacteria and viruses: a systematic review

Background: Nebulized aerosol therapy is widely used for treating respiratory diseases, including those caused by severe acute respiratory syndrome coronavirus-2. During pandemics, some guidelines recommend avoiding nebulizers, yet supporting evidence is limited. Objective: To undertake a systematic review of evidence on the risk of cross-infection linked to nebulizer use in healthcare settings. Data sources: Databases including Medline and Embase were searched from June 2020 to February 2024. Two independent reviewers conducted study selection and data extraction; discrepancies were resolved by a third reviewer. Data extraction: Risk of bias was assessed using the Newcastle–Ottawa Scale for case–control and cohort studies, an adapted version for cross-sectional studies, and a custom tool for experimental/simulation studies. Meta-analysis was performed on comparative clinical data. Certainty of evidence was rated using the Grading of Recommendation, Assessment, Development and Evaluation approach. Synthesis: Twenty-six studies met the inclusion criteria (six case–control, three cohort, one cross-sectional, four case series, 12 experimental/simulation). None of them reported that nebulizer use is free from risk of cross-infection. Meta-analysis of 10 comparative clinical studies (N=8536) found an association between nebulizer use and increased risk of infection (odds ratio 3.20, 95% confidence interval 1.59–6.44; P=0.0001), although certainty was low. Nine of 12 experimental/simulation studies demonstrated aerosol dispersion of particles or pathogens. Conclusions: Nebulizer exposure may elevate the risk of infection compared with non-exposure. Nebulizer use in hospital settings should be limited during pandemics or when cross-infection is a concern. When necessary, additional precautions are warranted.