Summary: High-flow nasal cannula versus continuous positive airway pressure in critical bronchiolitis: a randomized controlled pilot.

Topic: Primary Support

Cesar RG, Bispo BRP, Felix PHCA, et al.  High-flow nasal cannula versus continuous positive airway pressure in critical bronchiolitis: a randomized controlled pilot. J Pediatr Intensive Care. 2020 Dec;9(4):248-255. doi: 10.1055/s-0040-1709656

Cesar and colleagues conducted a randomized controlled pilot study to compare High Velocity Nasal Insufflation (HVNI) to continuous positive airway pressure (CPAP) and assess the feasibility of a larger international trial, hypothesizing that HVNI support would be equivalent to treatment with CPAP in infants with critical bronchiolitis.  

The study enrolled infants < 9 mo of age with critical bronchiolitis admitted to a tertiary PICU in Sao Paulo, Brazil. Patients in the CPAP group received 6 cm H2O pressure through a fitted nasal mask, while patients in the High Flow Nasal Cannula (HFNC) group received conditioned gas using HVNI up to 8 L/minute via nasal cannula. FiO2 was titrated to achieve an SPO2> 93%. Patients were treated with the assigned modality until recovery or progression to worsening respiratory failure requiring escalation of support (bi-level non-invasive positive pressure ventilation, or intubation). Failure was defined as worsening hypoxemic and/or hypercapnic respiratory failure despite maximal settings, requiring escalation of support as determined by the treating physician.  

In this pilot study, 63 patients were enrolled and randomized to either the CPAP group (n = 28) or HVNI group (n = 35). There were 10 treatment failures (35.7%) in the CPAP group and 13 (37.1%) in the HVNI group (p = 0.88), concluding that there was no statistical difference in the likelihood of needing intubation. Intubation was necessary in 3/10 patients in the CPAP group and 7/13 patients in the HFNC group. There was no significant difference in the duration of study support modality (2 days [1–3] vs 3 days [1–4], p = 0.316), PICU LOS (5 days [4–7] vs 5 [4–8],p = 0.459), and hospital LOS (8 [7–11] vs 9 [7–12], p = 0.95) which were similar between the CPAP and HVNI groups, respectively. 

The main purpose of the study was to obtain effect size data to assess the feasibility of a larger international trial of HFNC versus CPAP in critical bronchiolitis. The investigators estimated that such a trial would require at least 3,000 patients, or 1,500 patients per group.  

There were multiple study limitations reported. First of all, the relatively small pilot study precludes drawing more definitive conclusions regarding the equivalence of HVNI compared with CPAP as first-line treatment of critical bronchiolitis. In addition, the authors did not employ a crossover design, so it is impossible to determine how many patients who failed CPAP could have been rescued by HVNI, and vice versa. The study authors also did not include a true control group (i.e., standard oxygen therapy), choosing instead to compare what many consider standard therapy (CPAP) with a newer modality (HVNI). Furthermore, the results might not be completely generalizable to a broader critical bronchiolitis population as the patient sample was a specific higher risk group of young infants with moderate to severe critical bronchiolitis, predominantly caused by respiratory syncytial virus (RSV). Another limitation is that the study was planned and executed as “open label,” so the investigators and clinicians were aware of the treatment group allocation. Considering the relatively high threshold in the definition of treatment failure, the authors find it unlikely that knowledge of group allocation could have biased the results. Lastly, this study was conducted in a PICU with extensive experience in the use of CPAP in critical bronchiolitis but relatively new to the application of HVNI. 

The results concluded that in this single-center randomized controlled pilot study there was no statistical difference in the likelihood of needing intubation between CPAP (35.7%) and HVNI (37.1%) modalities.  HVNI was non-inferior to CPAP in supporting this group of high-risk infants with critical bronchiolitis. 

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