• asthma
• bronchial hyperresponsiveness
• bronchiolitis
• children
• respiratory sequelae
• wheezing.

Background: Bronchiolitis in the first months of life increases the risk of developing wheezing and/or asthma in the following years. The real role of bronchiolitis in determining the risk of future respiratory sequelae is not well understood yet.
Objectives: The purpose of our study was to evaluate the usefulness of a standardized follow up protocol to investigate the long-term outcomes of patients who have developed bronchiolitis and to compare the impact of different in-hospital therapeutic approaches.
Methods: Following a previous study of 346 patients previously hospitalized for bronchiolitis at the Paediatrics Operating Unit of the University Hospital of Pisa from January 2010 to December 2019, we contacted 234 patients by phone proposing a clinical evaluation and spirometry examinations years later.
Results: 102 patients agreed to participate to our study (57 males, mean age 8.5 ± 3.2 years, range 4-14 years). Their mean age at the index hospitalization was 3.6 ± 2.5 months (range 0-11 months). The recorded severity of bronchiolitis was mild, moderate, and severe in 44%, 49%, and 7% of patients, respectively, and the mean Bronchiolitis Severity Score (BSS) was 6.0 ± 2.7 (range 1–13).
In the study cohort, during hospitalization 61 patients (60%) tested positive for RSV and the second most detected virus was RV, followed by metapneumovirus. Over a half of the patients (n=55, 54%) developed wheezing at a mean age of 1.6 ± 1.1 years, while 12% were diagnosed with asthma, and 19% reported dyspnoea on exertion in the following years. Risk factors for developing respiratory sequelae were smoking exposure, family history of asthma, and allergies, which were all more prevalent in symptomatic children (all p<0.05), while no difference was found as regards sex, preterm birth, microbiological agents responsible for bronchiolitis, age at evaluation, and body-mass index.
Out of 88 patients undergoing a spirometry test at follow-up, a pathological FEV1 (z-score < -1.64) was reported in 6 cases, while 16 patients had a positive bronchodilator reversibility test.
Differences were found between the group of children treated for bronchiolitis before and after the publication of Italian Guidelines in 2014: the use of HFNC and nebulized 3% hypertonic saline solution was higher in children hospitalized after 2014, the use of inhaled and/or systemic corticosteroids was lower. On the other hand, the two groups were not different in term of sex, comorbidities, and risk factors. Similarly, no differences were observed as for bronchiolitis severity and microbiological agents. The incidence of wheezing was higher among patients treated according to the 2014 guidelines (63% vs 42%), while no differences were observed as for incidence of asthma.
CONCLUSIONS: In our cohort, over 50% of the patients previously hospitalized for bronchiolitis developed wheezing and/or asthma during a long-term follow-up. Since these children are at increased risk of developing respiratory sequelae, we suggest a strictly follow-up even years after bronchiolitis, to detect them in a timely manner, start a targeted therapy, and prevent further future respiratory problems.