Introduction: High flow nasal cannula (HFNC) oxygen therapy is a non-invasive form of respiratory support that is rapidly being taken up in paediatric intensive care units (PICU). For infants with bronchiolitis – who are the largest non-elective source of admissions to a PICU – there is some evidence that using HFNC therapy reduces the need for intubation and mechanical ventilation. The aim of this thesis is to explore, describe, critique and add to the evidence surrounding the use of HFNC therapy in the paediatric population for the management of respiratory distress.
Methodology: A case series analysis was undertaken to describe common pathophysiology presentations to a PICU that used HFNC therapy as a method of respiratory treatment. Consent was sought from individual patients who represented common presentations of patients requiring respiratory support in a PICU (asthma, bronchiolitis and cardiomyopathy). A Cochrane systematic review was undertaken to determine the evidence for the clinical application of HFNC in the paediatric population. However, there remains a paucity of literature on HFNC application in lower acuity settings. To address this, a pilot study was undertaken in the Paediatric Emergency Department (PED) of the Mater Children's Hospital (MCH), Brisbane, Australia, with infants with bronchiolitis who met the inclusion criteria and for whom parental consent was obtained. Once enrolled, HFNC therapy was commenced, and observations recorded at least hourly until treatment cessation. A comparison group was identified and included during the course of the study, consisting of all infants who were eligible but not enrolled during the study period. The study protocol detailed the clinical treatment of those infants in the trial group, and no other changes were made to the usual management of infants with bronchiolitis during the study period. The primary outcome of interest was PICU admission. Secondary outcomes included: physiological response to HFNC; adverse outcomes; intubation rates; and hospital and PICU length of stay.
Results: The case series analysis conducted indicated that HFNC therapy was successful in managing three patients with differing underlying pathophysiologies that caused respiratory distress. The Cochrane systematic review did not identify any studies that matched its inclusion criteria. Sixty-one infants were enrolled in the pilot study and 33 who met the inclusion criteria were later identified and formed the comparison group. Infants managed with HFNC therapy were four times less likely to require admission to PICU compared to those infants managed with standard low flow nasal oxygen therapy (OR 4.086, p=0.043). No infant, in either group, required intubation or mechanical ventilation. However, not all infants responded to HFNC therapy. Heart rate, respiratory rate and HiFOD score (a composite of physiological scores) indicated response to treatment over time (Generalised Linear Model p<0.001). The HFNC group successfully managed on the ward (Responders) had a mean reduction in heart rate of 13 bpm within 60 minutes of HFNC commencing. Whereas the heart rate of the HFNC group who were admitted to PICU (Non-Responders) increased (p=0.02). Likewise HiFOD scores also significantly reduced in the HFNC Responders with Non Responders maintaining or slightly decreasing their HiFOD score (p=0.006) at 60 minutes. A similar trend was observed with respiratory rate; however this did not become significant until 180 minutes (p=0.001).
Discussion: Clinical uptake of HFNC in the intensive care setting is increasing Intensive care settings are increasingly using HFNC therapy with reported clinical effect. However, the literature contains a paucity of evidence about its appropriate use and effectiveness, with only one small paediatric RCT conducted to date. The case series analysis revealed that using HFNC therapy may be safe and effective in the clinical management of infants with respiratory impairment. Further, the results of the pilot study indicate that HFNC therapy in low acuity settings, implemented as per the developed protocol, may reduce PICU admissions for infants with bronchiolitis. Additionally, the clinical reduction in heart rate and HiFOD scores at 60 minutes suggests that individual infants who receive HFNC therapy in a low acuity environment, but who do not respond within this time, may need to have their treatment reviewed and intervention escalated. These findings have implications for the effective management of bronchiolitis globally.
Conclusion: Bronchiolitis is the largest cause of PICU admissions. This thesis examines the evidence and builds on the extant literature by reporting a case series, a systematic review and a pilot study. Based on the results of this thesis, a trial of HFNC therapy in a low acuity setting may be considered, with anticipated clinical improvement evident in 60 minutes. This may indicate that the patient can be managed outside of an intensive care setting. Preventing PICU admissions will likely reduce both financial and social impact on hospitals and families.