Background: Lung ultrasound (LUS) has been shown to be an effective tool to rapidly diagnose certain causes of pediatric respiratory distress in the emergency department. However, very little is known about LUS findings in pediatric asthma outside of acute exacerbations. Objectives: The primary objective of this study was to characterize LUS findings in a cohort of pediatric patients with a definitive diagnosis of asthma, outside of an asthma exacerbation. Methods: Eligible patients, aged 6 to 17 years old and diagnosed with asthma, underwent LUS during an outpatient visit. LUS was conducted using a six-zone scanning protocol. A positive LUS was defined by one or more of the following: ≥3 B-lines per intercostal space, pulmonary consolidation and/or pleural anomaly. Images were interpreted by an expert sonographer blinded to patient clinical characteristics. Results: 52 patients were included. 10/52 patients had a positive LUS (19.2%, 95CI 8.3-30.1%). Of those with positive LUS findings, 8 had B lines, 7 had consolidations <1cm, 1 had a pleural line abnormality and 1 had a consolidation >1cm. Positive findings were seen in the right anterior and lateral zones in 60% of participants and were limited to 1-2 intercostal spaces within one lung zone in 100% of participants. Conclusion: To our knowledge, this is the first report of LUS findings in outpatient pediatric asthma. Positive LUS findings in asthmatic children can be seen outside of acute exacerbations. Such findings need to be taken into consideration when using LUS for the acute evaluation of a pediatric patient with asthma.

Background: Lung ultrasound (LUS) has been shown to be a useful clinical tool in pediatrics. LUS has been well studied in other respiratory conditions, but very little is known about the LUS findings of asthma. Objectives: The primary objective was to characterize LUS findings of pediatric patients before and after a chemically-induced bronchospasm. The secondary objective was to evaluate the effect of bronchodilators on the LUS findings. Methods: Eligible patients 6 to 17 years old presenting for a methacholine challenge test (MCT) in a pediatric respiratory clinic were recruited. LUS was performed before and after the MCT as well as after bronchodilator administration. LUS were analysed by an expert blinded to the patient characteristics and MCT results. Results: 44 patients were included in the study. 5 patients had positive LUS findings at baseline. 15 patients had a positive LUS following the MCT. There was a significant association between having a chemically-induced bronchospasm and a positive LUS post-MCT (p=0.05, odds ratio 5.3, 95% CI [1.0-27.7]) . Among patients who developed positive LUS findings post-MCT, 4 out of 9 returned to having a negative LUS post-bronchodilator administration. Conclusions: This is the first known report of an association between LUS findings and bronchospasm in pediatric patients. It is also the first documentation of resolution of LUS findings post-bronchodilator administration. Most LUS findings observed were small and limited to one or a few intercostal spaces. Further research is required to evaluate the effect of bronchodilators on LUS in the emergency department.