Reply: Residual airways: the lingering legacy of severe respiratory syncytial virus bronchiolitis

Extract

We thank Z.A. Naqvi and co-workers for their supportive and insightful comments on our study [1]. We fully agree that severe respiratory syncytial virus bronchiolitis requiring mechanical ventilation can have lasting respiratory consequences and that structured follow-up is essential. We also share the view that this need may extend beyond respiratory syncytial virus to other severe respiratory infections, and possibly to more children mechanically ventilated for more than 48 h.

Shareable abstract

Expiratory variability index is not a specific or fully validated gold standard for small airway disease. It works best as a screening or follow-up tool, but should be combined with other techniques such as oscillometry or MBW for confirmation. https://bit.ly/4n15use

Reply to Z.A. Naqvi and co-workers:

We thank Z.A. Naqvi and co-workers for their supportive and insightful comments on our study [1]. We fully agree that severe respiratory syncytial virus bronchiolitis requiring mechanical ventilation can have lasting respiratory consequences and that structured follow-up is essential. We also share the view that this need may extend beyond respiratory syncytial virus to other severe respiratory infections, and possibly to more children mechanically ventilated for more than 48 h.

Identifying which children require follow-up remains challenging. Our study involved a questionnaire and labour-intensive infant lung function testing [1]. Future work should focus on accessible, scalable assessment tools. Unfortunately, questionnaires alone do not discriminate well, as reported symptoms do not correlate with measured lung function. Systematic monitoring (including objective measures such as the Expiratory Variability Index (EVI)) and early rehabilitation may help close this gap. The EVI is a non-invasive, home-based measure of variability in tidal breathing flow–volume curves, which can help detect early or subclinical airway obstruction in infants who are too young for conventional lung function tests. However, it is not a specific or fully validated gold standard for small airway dysfunction. It works best as a screening or follow-up tool, but should ideally be combined with other techniques such as oscillometry or multiple breath washout for confirmation.

We therefore support the call for further research into predictive biomarkers, functional assessments, and the effectiveness of early interventions to ensure recovery extends beyond survival to optimal respiratory health.