Clinical Effect of Descent in Infants with Bronchiolitis Diagnosed at Altitude: A Prospective Multicenter Study

Poirier, Anne, Amélie Basso, Sarah Bonnet-Ducrot, Ellen Katranji, Sophia Cherif-Alami, Sophie Chateigner-Coelsch, Manon Navarre, Cécile Ricard, and Corentin Tanné. Clinical effect of descent in infants with bronchiolitis diagnosed at altitude: a prospective multicenter study. High Alt Med Biol. 26:134-139, 2025. Objective: This study aims to assess the clinical impact of descending to a lower altitude in infants with bronchiolitis diagnosed at an altitude above 1,000 m. Methods: We performed a prospective, observational, multicenter study during two consecutive winters (2022-2023 and 2023-2024). The diagnosis was made by local general practitioners (GPs) who then sent the patients who were younger than 1 year and had a Wang respiratory score (WRS) ≥4 to any of the five emergency departments (EDs) located at lower altitudes. The WRS, peripheral oxygen saturation (SpO₂), and respiratory rate (RR) recorded by the GPs and at the EDs were compared. Results: We included 74 infants (59% females, median age 5.4 [3.6-8.0] months). Compared with the median values recorded by the GPs at altitudes above 1,000 m, the median values at the lower-altitude EDs were significantly better for the WRS (5.0 vs. 6.0, p = 0.002), RR (50/min vs. 60/min, p = 0.001), and SpO₂ (97.0% vs. 91.5%, p < 0.001). Conclusion: Descending to a lower altitude significantly improved respiratory function in infants younger than 1 year with bronchiolitis diagnosed at altitudes above 1,000 m.