Inhaled Nitric Oxide for the Treatment of Acute Bronchiolitis A Multicenter Randomized Controlled Clinical Trial to Evaluate Dose Response

Rationale: Inhaled nitric oxide (iNO) has potential antiinflammatory, antimicrobial, and antiviral properties for patients with lower respiratory tract infections. Objectives: We compared the safety and efficacy of iNO administered in two concentrations in addition to standard supportive treatment (SST) compared with SST alone with the aim of improving clinical outcomes of infants with bronchiolitis. Methods: In this prospective, multicenter, double-blind, randomized controlled study, 89 infants hospitalized with moderate to severe bronchiolitis were randomly assigned to three treatment groups: 150 ppm NO plus SST (group 1), 85 ppm NO plus SST (group 2), and the control treatment (O₂/air plus SST) (group 3). Treatment was given for 40 minutes, four times each day, for up to 5 days. The primary endpoint was time to reach “fit for discharge.” This was a composite endpoint composed of both reaching a sustained oxygen saturation >92% on room air and reaching a clinical score <5. Secondary endpoints included time to reach sustained oxygen saturation >92% on room air, time to clinical score <5, and time to hospital discharge. Safety was assessed by the number of treatment-related adverse events (AEs) or serious AEs. Time-to-event efficacy outcomes were analyzed using a Cox proportional hazards regression model. Hazard ratios (HR) describe how many times more likely an individual is to experience an event, if such an individual receives NO rather than the control treatment during the observational period. Results: Group 1 demonstrated significant efficacy for time to reach fit to discharge compared with groups 2 (HR, 2.11; P = 0.041) and 3 (HR, 2.32; P = 0.049). Group 1 also demonstrated significant efficacy for time to hospital discharge compared with groups 2 (HR, 2.01; P = 0.046) and 3 (HR, 2.28; P = 0.043). No significant differences were observed between groups 2 and 3 for either endpoint. There were no differences between treatment groups in time to reach a clinical score <5. The iNO therapy was well tolerated, with no treatment-related serious AEs. Conclusions: Treatment with high-dose intermittent iNO at 150 ppm showed reduced time to clinical improvement compared with 85 ppm or control treatment of hospitalized infants with acute bronchiolitis. The 150-ppm iNO dose is well tolerated, with significant benefit compared with both standard therapy and 85 ppm iNO, improving respiratory outcomes and reducing length of stay.