N=1,472, <12 months, mode- rate bronchiolitis No differences in duration of oxygen therapy and ICU transfer Lower rate of treatment failure in HFNC group N=202, <24 months, moderate bronchiolitis The recent pediatric studies are summarized in Table 2. In addition, HFNC should be applied carefully in patients with a decreased level of consciousness, congenital heart disease, acute asthma, or chronic respiratory failure. We should know that contraindications for HFNC include upper airway abnormalities that may make HFNC ineffective or potentially dangerous, life-threatening hypoxia, hemodynamic instability, facial bone or skull base trauma, and pneumothorax. However, other indications have been studied, including asthma, sleep apnea, pneumonia, transport of a critical patient, and postextubation respiratory support. Many pediatric studies have included patients with acute bronchiolitis. Indications from the evidence in adults include acute hypoxemic respiratory failure, postextubation support, preoxygenation before intubation or during bronchoscopy, postoperative respiratory failure, and acute pulmonary edema. Recommended flow settings and cannula sizes for pediatric patients are summarized in Table 1.ĭuring recent decades, HFNC has been widely used in adult patients. That means that the appropriate outer diameter of the cannula is no more than two-thirds that of the nares. Manufacturers recommend that the cross-sectional area of the cannula be no more than 50% that of the nares because of the risk of unexpected elevations in airway pressure and the following risk of air leak. These results showed the importance of comprehensive understanding of the mechanism and optimal flow to ensure better outcomes.Ĭannula size varies by age and body weight. Interestingly, there was a large variation of maximal flow rates (L/min) in the different age groups among 67 hospitals. One study comparing the efficacy of HFNC and CPAP noted no differences in length of stay in the intensive care unit (ICU) and the need for mechanical ventilation between 2 L/kg/min of HFNC and 7 cmH2O of CPAP. Considering the flow limitation in adults (50–60 L/min), the reasonable flow rate is thought to be 1–2 L/kg/min up to 10 kg in patients, followed by an increase of 0.5 L/kg/min. However, patients were uncomfortable with 3 L/kg/min despite the same efficacy. Patients younger than 24 months of age tolerated the flow of 1–2 L/kg/min (up to 20 L/min) and 3 L/kg/min. Important randomized controlled studies conducted in patients with acute bronchiolitis provided information about appropriate flow. There is a lack of guidance about optimal flow in pediatric patients. Recent studies reported that limited pressure delivery of 2–4 cmH2O was measured in the pharynx and esophagus in children and adults with HFNC. In the experimental setting, positive lung-distending pressure increased as the flow increased from 0 to 12 L/min. Airway pressure generated from a high-flow system varies and depends on flow amount, cannula and nares sizes, and degree of mouth opening in an experimental study. The aforementioned principle, a higher flow setting than inspiratory demand, can be applied to patients of all ages. The development of clinical guidelines for HFNC, including flow settings, indications, and contraindications, device management, efficacy identification, and safety issues are needed, particularly in children.įlow setting and cannula size for pediatric patients Multicenter randomized studies are warranted to determine the feasibility and adherence of HFNC and continuous positive airway pressure in pediatric intensive care units. Several observational studies have shown that HFNC can be beneficial in acute asthma and other respiratory distress. HFNC can also reduce intubation and mechanical ventilation in children with respiratory failure. Randomized controlled studies suggest that HFNC can be used in cases of moderate to severe bronchiolitis upon initial low-flow oxygen failure. In children, flow level adjustments are crucial considering their maximal efficacy and complications. In preterm infants, HFNC can be used to prevent reintubation and initial noninvasive respiratory support after birth. The action mechanism of HFNC includes a decrease in nasopharyngeal resistance, washout of dead space, reduction in inflow of ambient air, and an increase in airway pressure. High-flow nasal cannula (HFNC) is a relatively safe and effective noninvasive ventilation method that was recently accepted as a treatment option for acute respiratory support before endotracheal intubation or invasive ventilation.
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