Introduction
In December 2019, a cluster of acute respiratory illnesses occurred in Hubei province, China, now known to be caused by a novel coronavirus, also known as SARS-CoV-2. It has spread globally since with more than 2 million cases reported as of April 2020.1 2 Severe hypoxaemic respiratory failure is by far the most common reason for admission to intensive care units (ICUs) due to COVID-19. In a report from Lombardi, Italy, of 1591 critically ill patients with COVID-19, 99% required respiratory support of at least supplemental oxygen and 88% (or 1150 patients) required invasive mechanical ventilation (IMV).3 Another retrospective review of Wuhan hospitalised patients, including patients without COVID-19, showed 52% required respiratory support, of which 55% needed mechanical ventilation.4 Mortality of patients with COVID-19 on IMV has been reported to in the range of 61%–96% in Italy, China and New York.3–5
High flow nasal therapy (HFNT) is a non-invasive oxygen delivery system that allows for administration of humidified air-oxygen blends as high as 60 L/min and a titratable fraction of inspired oxygen as high as 100%. HFNT has shown effectiveness in other severe viral respiratory illnesses like influenza A and H1N1.6 Use of HFNT has led to lower progression to invasive ventilation compared with other forms of non-invasive oxygen therapy.7–9 By decreasing the incidence of invasive ventilation, HFNT has the potential advantage of theoretically decreasing the incidence of ventilator-associated pneumonia (VAP), as well as reduction in hospital resources which can be critical during times of increasing strain on the healthcare system. When compared with non-invasive ventilation (NIV), the use of HFNT is associated with similar rates of reintubation due to postextubation respiratory failure.10 However, no short-term mortality benefit has been reported using HFNT to treat acute hypoxaemic respiratory failure.7 11 12
The Surviving Sepsis Guidelines for COVID-19 recommends using HFNT in patients with acute hypoxaemic respiratory failure due to COVID-19.13 However, others recommend against using HFNT fearing that it will create aerosolisation of the COVID-19 virus and increase transmission to healthcare providers.14–16 In the few case series that report HFNT use in patients with COVID-19, its usage has ranged from 4.8% to 63.5%.17–20 In a recent report of patients who succumbed to COVID-19 in China, 34.5% were placed on HFNT alone; the authors postulated that use of HFNT may have contributed to a delay in intubation thereby increasing mortality.21
Herein, we present a retrospective analysis of the outcomes of patients with COVID-19 with moderate-to-severe hypoxaemic respiratory failure receiving HFNT at our centre.