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A 3-month-old previously healthy baby presented with signs and symptoms of viral bronchiolitis. He suffered from tachypnoea (respiratory rate 70 breaths/min) and hypoxaemia (transcutaneously measured oxygen saturation (SpO2) of 89% at room air). Capillary blood gas analysis revealed a moderate hypercapnia (pCO2 of 60 mm Hg). The baby was admitted to the paediatric ward. The senior consultant ordered the use of low-flow oxygen therapy, but the junior consultant argued that high-flow nasal cannula (HFNC) oxygen therapy would be preferable as it improves patient comfort and might even prevent the need for endotracheal intubation.
Structured clinical question
In children with acute respiratory distress (patient), does HFNC oxygen therapy (intervention) reduce the need for endotracheal intubation (outcome) compared with conventional oxygen supplementation (control)?
Search strategy and outcome
PubMed was searched from inception until May 2013 using the following keywords: (children OR infants) AND (high flow OR high-flow) nasal (cannula OR prong). The search was limited to children aged 0–18 years and the English language. Studies including prematurely born infants with a gestational age corrected for postconceptional age less than 40 weeks were excluded. This resulted in 57 articles. Four articles were relevant to the search question, of which one was a review article. Related links and references in the selected articles were reviewed. A search of the Cochrane library yielded no additional articles.
Prevention of endotracheal intubation and invasive mechanical ventilation offers many advantages including avoiding injury to the airways and lungs, the use of sedative drugs and the prevention of the development of ventilator-associated pneumonia. As such, there is an increasing interest in non-invasive support of children with moderate-to-severe acute onset respiratory distress.1 In particular, the use of HFNC oxygen therapy outside the neonatal period has expanded dramatically and seems to be accepted as a first-line strategy for hospitalised children with moderate-to-severe acute onset respiratory distress, including patients with viral bronchiolitis, upper airway obstruction or postextubation. Data on the possible effect of HFNC in paediatric patients outside the neonatal population is emerging. HFNC allows the delivery of heated and humidified constant oxygen concentration with higher flow rates (>4 L/min) than with a conventional nasal cannula.2 The advantage is that less energy is required to condition the inspired air. Furthermore, higher flow rates may meet with the peak inspiratory flow rate generated by the patient with respiratory distress and reduce the anatomical dead space, resulting in increased CO2 elimination and clinical improvement.3–6 The use of HFNC resulted in significant beneficial changes in the Comfort Score, the Respiratory Distress Score, respiratory rate or the transcutaneous measured oxygen saturation (SpO2) in non-controlled, (retrospective) observational studies.7–9 Generation of a continuous distending pressure (CDP) is one of the presumed physiological mechanisms of HFNC. As such, HFNC has been proposed as potential alternative to nasal continuous positive airway pressure (NCPAP) following a small study performed in prematurely born infants. However, the highest level of CDP—especially in the presence of air leak—that can be generated is subject of debate.10 Clinical studies have shown nasopharyngeal CDP levels between ±3–4 cm H2O, irrespective of the presence of leak.7 ,11 Interestingly, sufficient flow (ie, >2 L/kg/min) may approximate the amount of CDP that has been proposed to be optimal during NCPAP in infants with viral bronchiolitis.12 ,13
It may thus be concluded from a physiological perspective that HFNC may be beneficial in patients with viral bronchiolitis, but it needs testing in randomised clinical trials (RCTs). At the same time, no RCTs investigating the effect of HFNC on the need for endotracheal intubation have been performed. Three observational studies have been published that may shed some light on this issue; all of them are confined to the paediatric intensive care unit population (table 1).8 ,9 ,14 Two of these studies were exclusively limited to infants with viral bronchiolitis, whereas in one study 23% of the patients were diagnosed with viral bronchiolitis.
The use of HFNC was significantly associated with a reduced overall endotracheal intubation rate in all three studies with a relatively low number needed to treat ranging from 3 to 9. This suggests that there may a role for HFNC in the prevention of the need for endotracheal intubation in children with viral bronchiolitis. However, there are some potential sources of bias that need to be discussed. The intubation rate prior to the use of HFNC was higher in two studies than previously reported, thus questioning the reproducibility of these findings.15 Furthermore, all included studies have a low level of evidence (ranging from level 3b to level 4) as they were not designed as RCTs and thus suffered from methodological flaws including selection bias. Apparently, not all of these studies may have been adequately powered to detect a difference in need for endotracheal intubation. Furthermore, as with any observational study, the association between HFNC and the reduced need for endotracheal intubation does not automatically indicate causality. The lack of a decision algorithm when to use a particular intervention is one of the methodological issues in retrospective observational studies leading to confounding by indication.16 The study by Wing et al is the only one reporting a decision algorithm for the use of HFNC. This indicates that selection bias cannot be ruled out in the other two studies. In addition, Schibler et al did not apply HFNC in all patients in their study. Ultimately, this can only be overcome by testing the effect of HFNC in a well-designed RCT. In fact, two RCTs comparing HFNC with conventional oxygen supplementation are currently underway and enrolling patients younger than 8 months of age with viral bronchiolitis (http://www.clinicaltrials.gov). Primary measures of outcome are the Clinical Severity Score and the length of hospital stay. Unfortunately, they do not address the question whether or not HFNC reduces the need for endotracheal intubation.
In conclusion, HFNC may reduce the need for endotracheal intubation but this requires testing in a RCT.
Clinical bottom line
The use of high-flow nasal cannula oxygen supplementation may reduce the need for endotracheal intubation in children with viral bronchiolitis (Grade C).
Contributor MK performed the analysis and wrote the manuscript.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
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