Clinical Question: Is the use of high humidity or low humidity best for treating moderate to severe croup?

Setting: Emergency department

Study Design: Randomized controlled trial (single-blinded)

Allocation: Concealed

Synopsis: Children with croup often are treated with humidity by the standard blow-by technique, which results in water droplets too large to reach the larynx. The investigators evaluated whether delivering particles sized for laryngeal deposition (i.e., 5 to 10 μm) is beneficial. A total of 140 otherwise healthy children three months to 10 years of age who presented to a pediatric emergency department with moderate to severe croup were enrolled in the study.

Patients were randomly assigned (concealed allocation) to receive 30 minutes of humidity using the traditional blow-by technique (commonly used placebo), controlled delivery of 40 percent humidity (optimally delivered placebo), or controlled delivery of 100 percent humidity with water particles of mass median diameter 6.21 μm. Complete follow-up occurred for all patients. Individuals assessing outcomes were blinded to treatment group assignment.

Using intention-to-treat analysis, improvement in the Westley croup scores from baseline to 30 minutes and from baseline to 60 minutes were similar in the three treatment groups. In addition, no differences were found between the treatment groups in secondary outcomes (e.g., pulse; respiratory rates; oxygen saturation changes; proportion of excellent responders; croup scores of 0 at study conclusion; proportion receiving dexamethasone, epinephrine, or requiring additional medical care or hospitalization). The study was 80 percent powered to detect a 1-point difference in croup scores.

Bottom Line: In children with moderate to severe croup, the use of controlled delivery of 100 percent humidity results in no greater improvement in croup scores than controlled delivery of 40 percent humidity or humidity by blow-by technique. (Level of Evidence: 1b)