AbstractBackgroundPulmonary exacerbations (PEx) are strong predictors of respiratory disease progression in children with cystic fibrosis (CwCF) and may be associated with persistent decreased lung function after acute management. Telemonitoring devices can be used for early detection and monitoring of PEx, but its utility is debated.Research QuestionWhich symptoms and telemonitoring spirometry characterics are related to outcome dynamics following initial PEx management?MethodsThis retrospective study included CwCF followed at Bordeaux University Hospital, France. All severe PEx episodes treated with intravenous (IV) antibiotics (ATB) between 1 January 2017 and 31 December 2021 in CwCF using home telemonitoring were analyzed. Symptoms and home spirometry data were collected 45 days before and up to 60 days after each IV ATB course. We defined three response profiles based on terciles of baseline forced expiratory volume in 1 s (FEV1) recovery.ResultsA total of 346 IV ATB courses for PEx were administered to 65 CwCF during the study period. The drop in FEV1 became significant 8 days before IV ATB initiation. Forty‐one percent of IV ATB courses failed to restore baseline FEV1. The magnitude of FEV1 drop and a greater delay in the initiation of treatment correlated with a low response level. On the 14th day of the IV treatment, a FEV1 recovery less than 94% of baseline was associated with a nonresponder profile.InterpretationHome spirometry may facilitate the early recognition of PEx to implement earlier interventions. This study also provides an outcome lung function threshold which identifies low responders to IV ATB.