Predicting failure of high flow nasal cannula in bronchiolitis: a systematic review

Background: In some infants with bronchiolitis High-Flow Nasal Cannula (HFNC) oxygen therapy fails and other respiratory support is needed. Aim: Systematically review evidence around prognostic factors associated with HFNC failure in bronchiolitis. Methods: We included observational studies of infants Results: We included 13 studies (6/13 multicentre, 7/13 observational [6/7 retrospective]), involving 3,114 infants (85% had bronchiolitis). Studies were of reasonable quality, but considerable heterogeneity and low generalisability rendered overall quality of evidence very low. Reporting of methods, analysis and results were often inadequate. No infant characteristics (age/weight/comorbidity; 10 studies), or clinical observations/severity scores (6 studies) consistently predicted HFNC failure. When reported, markers of respiratory acidosis at HFNC initiation more consistently demonstrated statistically significant association with treatment failure (pH in 4/5 studies; pCO2 in 3/5 studies). Conclusion: No factors consistently predict failure of HFNC in bronchiolitis, but the quality of the evidence is very low. Respiratory acidosis may predict treatment failure but should be tested in prospective multicentre studies before being used to select respiratory support modalities for individual infants with bronchiolitis.