High‐Flow Nasal Cannula and Virological Surveillance in Severe Bronchiolitis: A Retrospective PICU Study in Southern Brazil

Acute Viral Bronchiolitis (AVB) is a leading cause of hospitalization among infants and young children, with Human orthopneumovirus (Respiratory Syncytial Virus [RSV]) representing the most prevalent etiologic agent. Despite its clinical relevance, data describing the epidemiological profile of AVB cases in Pediatric Intensive Care Units (PICUs) remain limited, particularly regarding advanced statistical modeling adjusting for modern respiratory support and testing biases. This observational, retrospective, and analytical study included 210 children aged 0–2 years with laboratory‐confirmed AVB admitted to a private PICU in Southern Brazil between 2019 and 2023. To stabilize analyses affected by zero‐event cells, Firth's penalized maximum likelihood logistic regression was utilized. Multivariate logistic regression was performed to assess the independent impact of high‐flow oxygen therapies.The mean age was 5.76 months (SD = 4.46). The mean Modified Tal Score at admission was 7.4. RSV was the most frequently identified virus (72.4%). The apparent increase in viral diversity in later years, specifically Rhinovirus A/B/C (23.4%) and Enterovirus (7.7%), reflects a profound detection bias introduced by the adoption of an expanded 24‐pathogen multiplex panel rather than a true epidemiological shift. Adjusted multivariate analysis demonstrated that HFNC use was independently associated with lower odds of invasive mechanical ventilation after adjustment for measured confounders (aOR = 0.54, 95% CI: 0.31 to 0.92; p  = 0.02).These findings highlight the impact of testing methodologies on virological surveillance. Rigorous adjusted analyses confirm that the early application of modern non‐invasive respiratory support is independently associated with lower odds of invasive mechanical ventilation.