High-flow nasal oxygen (HFNO) therapy for severe COVID-19 patients with hypoxaemic respiratory failure (HRF)is feasible and more almost half of those who receive it can be successfully weaned without the need for mechanical ventilation, found a study at two South African tertiary hospitals.
It is the largest published study of its kind to date, appearing in EClinical Medicine, and builds on evidence for the benefits of HFNO described in a smaller French study, published in August.
The survival rate is lower than that described by the researchers in a letter published in the SA Medical Journal on 7 May, which considered the early evidence from a very small number of patients. The SAMJ letter compared the outcomes of just 13 patients, seven of whom were given HFNO, and six of whom were ventilated. In that small sample, all the HFNO patients survived, but only one of the ventilated patients did.
HFNO therapy is non-invasive, and uses a machine to propel warm, humidified, oxygen-enriched air into a tube in a patient’s nose at a rate of up to 60 litres per minute. It has several advantages over mechanical ventilation, as patients do not need to be sedated and can still speak and eat independently. It requires fewer specialised skills from healthcare professional, and can be provided outside an intensive care unit.
The study was conducted at Groote Schuur and Tygerberg hospitals in the Western Cape and included 293 patients. Half the patients (52%) were effectively treated with HFNO and discharged from hospital. If they had not been given HFNO, they would have had to have been placed on mechanical ventilators, which international studies have shown to have a mortality rate ranging from 60%-95%.
Failure comprised intubation or death on HFNO. The mortality rate among amongst HFNO failures with outcomes was 129/140 (92%).
Background: The utility of heated and humidified high-flow nasal oxygen (HFNO) for severe COVID-19-related hypoxaemic respiratory failure (HRF), particularly in settings with limited access to intensive care unit (ICU) resources, remains unclear, and predictors of outcome have been poorly studied.
Methods: We included consecutive patients with COVID-19-related HRF treated with HFNO at two tertiary hospitals in Cape Town, South Africa. The primary outcome was the proportion of patients who were successfully weaned from HFNO, whilst failure comprised intubation or death on HFNO.
Findings: The median (IQR) arterial oxygen partial pressure to fraction inspired oxygen ratio (PaO2/FiO2) was 68 (54–92) in 293 enroled patients. Of these, 137/293 (47%) of patients [PaO2/FiO2 76 (63–93)] were successfully weaned from HFNO. The median duration of HFNO was 6 (3–9) in those successfully treated versus 2 (1–5) days in those who failed (p<0.001). A higher ratio of oxygen saturation/FiO2 to respiratory rate within 6 h (ROX-6 score) after HFNO commencement was associated with HFNO success (ROX-6; AHR 0.43, 0.31–0.60), as was use of steroids (AHR 0.35, 95%CI 0.19–0.64). A ROX-6 score of ≥3.7 was 80% predictive of successful weaning whilst ROX-6 ≤ 2.2 was 74% predictive of failure. In total, 139 patents (52%) survived to hospital discharge, whilst mortality amongst HFNO failures with outcomes was 129/140 (92%).
Interpretation: In a resource-constrained setting, HFNO for severe COVID-19 HRF is feasible and more almost half of those who receive it can be successfully weaned without the need for mechanical ventilation.
Gregory L Calligaro, Usha Lalla, Gordon Audley,Phindile Gina, Malcolm G Miller, Marc Mendelson, Sipho Dlamini, Sean Wasserman, Graeme Meintjes, Jonathan Peter, Dion Levin, Joel A Dave, Ntobeko Ntusi, Stuart Meier, Francesca Little, Desiree L Moodley, Elizabeth H Louw, Andre Nortje, Arifa Parker, Jantjie J Taljaard, Brian W Allwood, Keertan Dheda, Coenraad FN Koegelenberg
SAMJ letter authors
U Lalla, BW Allwood, EH Louw, A Nortje, A Parker, JJ Taljaard, D Moodley, CFN Koegelenberg
[link url="https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(20)30314-X/fulltext"]EClinicalMedicine Full text[/link]
[link url="http://www.samj.org.za/index.php/samj/article/view/12941/9235"]SA Medical Journal letter[/link]