1-INTRODUCTION
Acute bronchiolitis is a common disease characterized by inflammation, edema, and necrosis in the lower respiratory airways. It continues a substantial health burden for infants and young children worldwide.1 In the United States of America (USA), approximately 2-3% of children younger than 12 months of age (accounts for 57.000-120.000 hospitalizations annually) are hospitalized with respiratory syncytial virus-related bronchiolitis.2–5The total estimated inpatient charges exceed $1.7 billion annually in the USA.6 Similarly, from 2002 through 2014 in Australia and New Zealand, increasing the admission to the intensive care unit (ICU) due to bronchiolitis has raised health care costs.7 The treatment of this frequent and costly condition is mainly supportive, including hydration, oxygen supplementation, and respiratory support.8 On the other hand, high-flow nasal cannula oxygen (HFNCO) becomes an essential and promising treatment modality for bronchiolitis.1,8
Initial observational and physiological studies using HFNCO determined improved gas exchange, decreased respiratory effort, and reduced mechanical ventilation (MV) rates.9,10 Milani et al.11 showed that HFNCO was efficacious not only in improving respiratory rate (RR) and respiratory effort but also in reducing the duration of oxygen therapy and length of hospital stay (LOS). In contrast, two recent randomized, controlled trials12,13 comparing the effects of HFNCO and LFO in infants with bronchiolitis found no statistically changes in heart rate (HR), RR, duration of oxygen therapy, and LOS. Similar to these results, there have been controversial reports regarding bronchiolitis severity scores. While Ballestero et al.14 found that pulmonary score decreased in more patients with HFNCO (53%) compared to those with conventional oxygen therapy (28%), Chen et al.15did not show a significant decrease in respiratory distress assessment instrument over time between HFNCO and standard dry oxygen. A 2014 Cochrane review16 proposed that there has been insufficient evidence to identify the effectiveness of HFNCO. Similarly, the American Academy of Pediatrics (AAP) Bronchiolitis Guideline17 concluded that not enough randomized clinical trials have been present to recommend its routine use despite the promising. We aimed to examine whether HFNCO provided enhanced respiratory support, evidenced by a notable improvement in HR, RR, and clinical respiratory score (CRS), in infants with bronchiolitis and hypoxemia admitted to the general pediatric ward.