Child's respiratory impedance will be continuously recorded using the Leo device during hospital/ED stay after consent and enrollment, and then during 7 days at home after discharge. The Leo device provides no intervention, and will only monitoring chest impedance for the worn period. Oscillometry and spirometry testing and flow volume assessment using PNT will be performed during study visits with Leo device attached.

After consent and enrollment, the child's respiratory impedance will be continuously recorded using the Leo device throughout the day and night during the entire hospital stay or ED visit. The device may be taken off for up to 1 hour per day (i.e., break during bath / shower time). The device will be applied to the skin overlying the mid-sternum area on the chest wall after cleaning of the skin with an alcohol swab after consent has been obtained. The device will be changed every 72 hours or earlier, by the participant's guardian, depending on signs of defect in the signal quality or battery exhaustion, based on daily check of the signal by the research team. Remote monitoring of the child's chest impedance will continue using the Leo device after discharge from hospital/ED for 7 days.

Asthma severity measures will be determined through oscillometry test at baseline and follow-up visit. Leo measurements will be assessed for agreement with oscillometry measures.

Self-reported asthma flare-up diary score will be measured daily during the remote (at home) period in between visits.

Questionnaire will be used to determine asthma severity during baseline and follow-up visit. CASI scores include five domains: day symptoms and albuterol use, night symptoms and albuterol use, controller treatment, lung function measures, and exacerbations. Range is from 0 -17, with a higher score indicating worse asthma severity

Propeller sensor will include measures of time stamped data of inhaler usage (controller and rescue inhalers)