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High Flow Oxygen Therapy in times of COVID:

Updated: Jan 28, 2022

Resources and Links to Evidence-Based Best Practices and Patient Education

High Flow Nasal Oxygen has been used for respiratory-compromised patients and recently has been studied for its promising results in treating COVID-19 patients in a variety of settings. This post will link you to several studies, assessments, and recommendations to help you understand best practices and limitations in the use of High Flow Nasal Oxygen.

You can head right to the articles listed below by clicking the titles or continue reading to see a summary and bullet points for each article.

High-flow nasal cannula for COVID-19 patients: low risk of bio-aerosol dispersion

The utility of high-flow nasal oxygen for severe COVID-19 pneumonia in a resource-constrained setting: A multi-centre prospective observational study.

(Demoule and Dres 2017). jump to summary. go to full article.

(Drake 2017). jump to summary. go to full article.

Patient Education: High Flow Oxygen Therapy. go to full article.


Three large clusters of SARS-CoV-2 infected patients were detected in France at the end of February 2020. High-flow nasal oxygen (HFNO, Airvo2TM, Fisher and Paykel Healthcare) has been a standard therapy for non-hypercapnic acute hypoxemic respiratory failure in Vannes hospital since the publication of the FLORALI trial in 2015 [3]. This report describes the use of HFNO to manage SARS-CoV-2 infected patients with respiratory failure on the pulmonology ward rather than in an ICU.


Graphic representation of the 27 COVID-19 patients treated with high-flow nasal oxygen (HFNO) in pulmonology department of Vannes hospital, France.

The use of HFNO in COVID-19 raises two issues: its safety and its effectiveness.


While these results should be confirmed in larger studies, we believe that our data strongly suggest that SARS-CoV2 infected patients with non-hypercapnic acute hypoxemic respiratory failure can benefit from HFNO outside an ICU. The technique appears to be safe for HCWs and could well liberate critical ICU resources.


High-flow nasal cannula for COVID-19 patients: low risk of bio-aerosol dispersion

(Li et at. 2020)


Among patients with acute hypoxaemic respiratory failure, HFNC was proven to avoid intubation compared to conventional oxygen devices [2, 3]. However, there is an important concern that HFNC may increase bio-aerosol dispersion in the environment due to the high gas flow used. The increased dispersion might favour transmission of infectious agents (such as SARS-CoV-2) carried in aerosol droplets generated by the infected patient. This concern is reflected in the limited use of HFNC in the first clinical study reporting 21 patients with COVID-19 in Washington State (USA), where only one patient used HFNC [4]. In contrast, a broad utilisation was observed in the study by Yang et al. [5] from Wuhan, China, where 33 out of 52 intensive care unit (ICU) patients were treated with HFNC.

There appears to be an uncertainty and a trend to avoid HFNC among COVID-19 patients in the western world, thus increasing early intubation rates and potentially associated harms such as sedation and prolonged ICU stay but also intubation procedures per se, which represent a high-risk situation for viral exposure. Early intubation increases the demand for ventilators, contributing to the critical shortage reported worldwide. Avoiding or delaying invasive mechanical ventilation could substantially reduce immediate demand for ventilators. Thus, we aim to discuss the scientific evidence supporting the risk of HFNC-induced bio-aerosol dispersion in the COVID-19 context.


In vitro and clinical studies have demonstrated that placing a simple surgical protection mask on patients significantly reduces dispersion distance [9] and levels of virus-infected bio-aerosol 20 cm away from patients while coughing [10]. Such a surgical mask can be worn by a patient oxygenated through a nasal cannula (standard nasal cannula or HFNC) but not when using simple, non-rebreathing or Venturi oxygen masks.

Taken together, compared to oxygen therapy with a mask, the utilisation of HFNC does not increase either dispersion or microbiological contamination into the environment. The patient being able to wear a surgical mask on top of HFNC, in order to reduce the aerosol transmission during coughing or sneezing, represents an additional benefit.


In conclusion, massive numbers of clinicians have been infected during the COVID-19 outbreak, which has raised concerns around implementing aerosol-generating procedures. Consequently, there appears to be a trend to avoid HFNC. The scientific evidence of generation and dispersion of bio-aerosols via HFNC summarised here shows a similar risk to standard oxygen masks. HFNC prongs with a surgical mask on the patient's face could thus be a reasonable practice that may benefit hypoxaemic COVID-19 patients and avoid intubation.

Clinicians should consider moving away from the dogma restraining the use of HFNC among COVID-19 patients.


The utility of high-flow nasal oxygen for severe COVID-19 pneumonia in a resource-constrained setting: A multi-centre prospective observational study.

(Calligaro et al. 2020)

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%).
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.

In conclusion, in a resource-constrained setting where access to ICU care and mechanical ventilation is limited, HFNO for severe COVID-19 HRF is feasible and deliverable even in a ward-based non-critical care environment, and more almost half of those who receive it can be successfully weaned without the need for mechanical ventilation. Conversely, mortality in patients who fail HFNO is high.


(Demoule and Dres 2017)


The purpose of the present review is to provide clinicians with the most recent information on HFNO and to discuss its benefits and risks in its most common indications.


How does high flow nasal oxygen work?
What benefits can we expect from high flow nasal oxygen?
In hypoxemic acute respiratory failure, high flow nasal oxygen may produce a lower intubation rate than standard oxygen and non-invasive ventilation in the most severely hypoxemic patients
High flow nasal oxygen is a promising approach to prevent reintubation, but it should be used carefully in high-risk patients
High flow nasal oxygen is a valuable alternative to non-invasive ventilation to prevent acute respiratory failure in the post-surgical setting
Other settings in which high flow nasal oxygen could be beneficial but require further investigation
Which precautions should be taken when using high flow nasal oxygen?


Over the past several years, a growing number of studies have suggested the potential benefit of HFNO in preventing intubation or reintubation in ICU patients who are either admitted for de novo acute respiratory failure or mechanically ventilated for surgery. Although HFNO appears to be a promising therapy in the ICU, additional studies are needed to define more precisely the subgroups of patients who are most likely to benefit from HFNO. Clinicians willing to use HFNO should know that HFNO might have deleterious effects, especially if it is not used adequately. As with any novel therapy, clinicians should learn how to use and implement HFNO progressively and cautiously.


(Demoule and Dres 2017)


High-flow nasal cannula oxygenation has been shown to have similar, and in some cases superior clinical efficacy compared with conventional low-flow oxygen supplementation and noninvasive positive pressure ventilation in acute hypoxemic respiratory failure. High-flow nasal cannula oxygenation also prevents reintubations in medical and postoperative surgical populations, provides preoxygenation for laryngoscopy, and supports oxygenation during bronchoscopy. This review examines the evidence for high-flow nasal cannula oxygenation use in adults, including a focus on the unique effects of high flow on respiratory physiology and keys for tailoring flow for specific clinical scenarios.

High-flow nasal cannula (HFNC) oxygenation has become an increasingly popular therapy for hypoxemic respiratory failure.

Physiologic Effects of High-Flow Nasal Cannula Oxygenation:

Physiologic benefits of high-flow nasal cannula compared with conventional low-flow oxygenation  Improved oxygenation Decreased anatomic dead space owing to washout of upper airway Decreased metabolic cost of breathing/reduced carbon dioxide generation Generation of positive nasopharyngeal and tracheal airway pressureImproved work of breathing Preconditioning of inspired gas (heated and humidified) Better secretion clearance Superior comfort Reduced room air entrainment HFNC also improves gas transfer and increases lung volumes.
Physiologic benefits of high-flow nasal cannula compared with conventional low-flow oxygenation

Acute Hypoxemic Respiratory Failure.

Acute hypoxemic respiratory failure is a primary reason for instituting HFNC therapy.

A Table of Prospective trials evaluating high-flow nasal cannula oxygenation in medical patients

Overall, these trials build on prior nonrandomized studies that cumulatively support HFNC use for hypoxemic respiratory failure (5, 2026) (Table 2). Authors of a recent meta-analysis of these studies that included over 3,000 subjects agreed. HFNC reduced the need for endotracheal intubation compared with conventional oxygen and NIV (odds ratio, 0.60; 95% confidence interval, 0.41–0.86) (27) and should be considered as first-line therapy for patients with acute hypoxemic respiratory failure.

Table 3. Prospective trials of high-flow nasal cannula oxygenation in surgical patients (Prevention of reintubation after cardiac surgery)

Table 4. Prospective trials of high-flow nasal cannula oxygenation for intubation and bronchoscopy (Preoxygenation and apneic oxygenation for intubation)

Future Research Directions


(Hyzy 2021)


This topic review discusses the practical application and clinical uses of HFNC in adults. Oxygen delivery systems for infants and children are discussed separately.

Physical Applications and Settings


Setting Recommendations

HFNC versus low flow oxygen

HFNC versus noninvasive ventilation

Postextubation support

Postoperative respiratory failure

Intubation support

Contraindications and complications

Society Guideline Links


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