How to use high flow therapy in COVID-19 acute hypoxemic respiratory failure

Author: Aude Garnero, Intensivist, Hôpital Sainte Musse, Toulon, France, Reviewer: Jean-Michel Arnal, Süha Demirakca

High flow therapy (HFT) has been used widely during the COVID-19 pandemic. Published clinical experience is based mainly on retrospective studies and describes the main settings and the failure rate.

In these studies, the flow setting at the start of HFT was between 30 L/min and 60 L/min (1-9). Oxygen was between 60% and 100% at initiation (1, 5), and adjusted to target SpO2 of greater than 90% (2, 8).

The temperature was set to between 31°C and 37 °C (2, 4, 7, 8).

Flow is usually set to cover the patient’s minute volume ventilation, and is then adjusted according to the patient’s tolerance. Oxygen is adjusted dynamically based on SpO2 values and blood gas analysis. The temperature is adjusted according to the patient’s comfort, but the higher the temperature, the higher the humidity provided.

Clinical protocol

1. When to start HFT?

If a COVID-19 patient remains hypoxemic despite conventional oxygen therapy, recommendations suggest using HFT over conventional oxygen therapy (10).

2. Initial settings:

  • Flow = 60 L/min
  • Temperature = 37° to provide optimal humidity
  • Oxygen = 100%

3. Adjustments:

  • Oxygen should be adjusted to target SpO2 between 92% and 96% (10)
  • Use oxygen flushes (oxygen set at 100% for 2 minutes) before each mobilization
  • With such a high flow, a temperature setting of 37°C is usually well tolerated

4. How to wean from HFT?

  • When the patient’s condition has stabilized (i.e., 12 hours with oxygen at 50%), try to decrease Flow to 50 L/min
  • When the patient has 40% Oxygen, decrease the flow to 40 L/min
  • Try to stop HFT each day when Oxygen is less than 40% and Flow is less than 40 L/min

Adjunctive treatments

When Oxygen is higher than 50%, HFT can be combined with prone positioning or CPAP.



  1. Hu M, Zhou Q, Zheng R, et al. Application of high-flow nasal cannula in hypoxemic patients with COVID-19: a retrospective cohort study. BMC Pulm Med. 2020 Dec 24;20(1):324
  2. Xu J, Yang X, Huang C, et al. A Novel Risk-Stratification Models of the High-Flow Nasal Cannula Therapy in COVID-19 Patients With Hypoxemic Respiratory Failure. Front Med (Lausanne). 2020 Dec 8;7:607821
  3. Demoule A, Vieillard Baron A, Darmon M, et al. High-Flow Nasal Cannula in Critically III Patients with Severe COVID-19. Am J Respir Crit Care Med. 2020 Oct 1;202(7):1039-1042
  4. Patel M, Gangemi A, Marron R, et al. Retrospective analysis of high flow nasal therapy in COVID-19-related moderate-to-severe hypoxaemic respiratory failure. BMJ Open Respir Res. 2020 Aug;7(1):e000650
  5. Zucman N, Mullaert J, Roux D, et al.; Contributors. Prediction of outcome of nasal high flow use during COVID-19-related acute hypoxemic respiratory failure. Intensive Care Med. 2020 Oct;46(10):1924-1926
  6. Calligaro GL, Lalla U, Audley G, et al. The utility of high-flow nasal oxygen for severe COVID-19 pneumonia in a resource-constrained setting: A multi-centre prospective observational study EClinicalMedicine. 2020 Nov;28:100570
  7. Panadero C, Abad-Fernández A, Rio-Ramirez MT, et al. High-flow nasal cannula for Acute Respiratory Distress Syndrome (ARDS) due to COVID-19. Multidiscip Respir Med. 2020 Sep 16;15(1):693
  8. Montiel V, Robert A, Robert A, et al. Surgical mask on top of high-flow nasal cannula improves oxygenation in critically ill COVID-19 patients with hypoxemic respiratory failure. Ann Intensive Care. 2020 Sep 29;10(1):125
  9. Bonnet N, Martin O, Boubaya M, et al. High flow nasal oxygen therapy to avoid invasive mechanical ventilation in SARS-CoV-2 pneumonia: a retrospective study. Ann Intensive Care. 2021 Feb 27;11(1):37
  10. Alhazzani W, Møller MH, Arabi YM, et al. Surviving Sepsis Campaign: Guidelines on the Management of Critically Ill Adults with Coronavirus Disease 2019 (COVID-19). Crit Care Med. 2020 Jun;48(6):e440-e469

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high flow, Hft, hfot, oxygen therapy, settings, adjustments, covid, pneumonia

Date of Printing: 30.06.2022
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Date of Printing: 30.06.2022
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