Clinical outcomes of high-flow nasal cannula in COVID-19 associated postextubation respiratory failure. A single-centre case series

Introduction
A high-flow nasal cannula (HFNC) is an alternative device for oxygena­tion, which improves gas exchange and reduces the work of breathing. Postextubation respiratory failure causes increased morbidity and mortality. HFNC has been widely employed during the COVID-19 pandemic. The purpose of this paper is to report a single-centre experience on the effectiveness and safety of HFNC in weaning COVID-19 patients.

Material and methods
Nine patients showed severe acute respiratory failure and interstitial pneumonia due to SARS-CoV-2. After mechanical ventilation (5 Helmet CPAP, 4 invasive mechanical ventilation), they were de-escalated to HFNC. Settings were: 34–37°C, flow from 50 to 60 L min-1. FiO2 was set to achieve appropriate SpO2.

Results
Nine patients (4 females; age 63 ± 13.27 years; BMI 27.2 ± 4.27) showed a baseline PaO2/FiO2 of 109 ± 45 mm Hg. After a long course of ventilation all patients improved (PaO2/FiO2 336 ± 72 mm Hg). Immediately after initiation of HFNC (2 hours), PaO2/FiO2 was 254 ± 69.3 mm Hg. Mean ROX index at two hours was 11.17 (range: 7.38–14.4). It was consistent with low risk of HFNC failure. No difference was observed on lactate. After 48 hours of HFNC oxygen therapy (day 3), mean PaO2/FiO2 increased to 396 ± 83.5 mm Hg. All patients recovered from respiratory failure after 7 ± 4.1 days.

Conclusions
HFNC might be helpful in weaning COVID-19 respiratory failure. Effectiveness and comfort should be assessed between 2 and 48 hours. Clinical outcomes, oxygenation, and ROX index should be considered, to rule out the need for intubation. Further evidence is required for firm conclusions.