High Flow Nasal Cannula Oxygen in COVID-19;still an important role to play

ABSTRACT

Introduction: High flow nasal cannula oxygen (HFNC) has a firm evidence base in the management of hypoxaemic respiratory failure. It has been shown to reduce mortality and increase ventilator free days when compared with use of standard oxygen or continuous positive airway pressure (CPAP), and it has been shown to reduce intubation rates in patients with a P F ratio of <200mmHg.1 However, provisional data from the use of HFNC in COVID-19 suggest no significant reduction in intubation rates and no mortality benefit over conventional oxygen therapy or CPAP.2 These contradictory findings complicate our understanding of any potential role for HFNC in COVID-19. In our organisation, all patients with COVID-19 who remained hypoxic despite standard oxygen therapy were initially managed with HFNC and only if they failed this modality were then trialled on CPAP or intubated for invasive mechanical ventilation. HFNC was provided on our physician led Respiratory Support Unit (RSU) with daily critical care input. Our approach differs to that employed in the most recent multicentre randomised controlled trial of respiratory support in COVID-19 and therefore offers the opportunity to understand how HFNC may be of benefit in patients with COVID-19. Objectives: To explore the potential role and safety for HFNC in COVID-19. Methods: Retrospective analysis of all patients with COVID-19 admitted to a single NHS acute Trust between March 2020 and February 2021, who required escalation of respiratory support to HFNC with or without subsequent CPAP or intubation. Data collected included patient demographics, comorbidities, respiratory support requirements, ceiling of treatment and outcomes. Logistic regression analysis was used to compare mortality rates for patients who did or did not receive HFNC. Results: One hundred and forty-seven patients met inclusion criteria of whom fifty-five (37%) were managed solely on the Respiratory Support Unit (RSU). Nineteen patients (13%) had HFNC as their ceiling of care, of whom nine died. Of those patients deemed appropriate for full escalation, fifty-four (37%) received only HFNC and thirty-two (22%) subsequently required intubation after a trial of HFNC. The relative risk of mortality for patients who received HFNC prior to intubation compared to those who were intubated without HFNC was 0.48 (95% CI 0.26-0.89). There were no safety concerns associated with HFNC. Conclusion: Our data suggests that HFNC may offer survival benefit in those with care limitations in organ support, as demonstrated by our survival rate of 53% in this patient cohort. HFNC is generally well tolerated and is associated with fewer adverse events than other forms of non-invasive respiratory support. HFNC can be employed as a safe tool for assessing patients' respiratory support requirements and monitoring trajectory in RSUs, sparing ICU capacity in healthcare systems under strain. Furthermore, it is associated with a favourable mortality profile in those who subsequently require intubation (34% mortality), particularly when compared with the UK national average for mortality in COVID-19 ventilated patients (50%). HFNC may therefore still have a role in the management of patients with COVID-19 with acute hypoxaemic respiratory failure and this warrants further examination.