What is high-flow nasal cannula (HFNC)?

Michael Allison, MD
26th Nov 2020

High-flow nasal cannula (HFNC), also referred to as nasal high flow (NHF), is a therapy that has gained traction in the past decade and is sometimes lumped together with the use of noninvasive ventilation (NIV). Since it differs from noninvasive ventilation, it will be important to highlight differences between these two therapies.


Oxygen delivery with HFNC

Let’s take a moment to remember the traditional nasal cannula. When connected to wall oxygen, this cannula can deliver oxygen at flow rates from 1 to 6 L / min for extended periods of time. Higher flow rates are not well tolerated due to nasal irritation and discomfort.

High-flow nasal cannula, or HFNC, is a system that allows oxygen to be delivered to patients at very high flow rates. In adults, it can be titrated from 20 L / min up to 60 L / min! By using specialized nasal cannulas, heating the circuit to body temperature and humidifying the air, these high rates can be delivered with very good patient tolerance. 

Like the flow rate, fraction of inspired oxygen (FIO2) can be precisely titrated as well. An air-oxygen blender can take 100% wall oxygen, mix it with room air, and deliver a FIO2 between 21 and 100%.

Woman with nasal cannula, O2 cloud. Illustration

Figure 1. High-flow nasal cannula (HFNC) systems use specialized nasal cannulas that allow oxygen to be delivered at an FIO2 of 21–100% with high flow rates of 20–60 L / min. Heating the circuit to body temperature and humidifying the air allows these high flow rates to be well tolerated by the patient. 


How is HFNC like NIV?

HFNC is similar to NIV in that it reduces the entrainment of room air and allows a more precise amount of oxygen to be delivered. It requires a specialized interface that sits in the nose with larger bore openings. It can provide respiratory support to patients with respiratory failure due to hypoxia.


How does HFNC differ from NIV?

HFNC differs to NIV in that it provides less ventilatory support. You set a flow rate instead of setting inspiratory and expiratory pressures. Therefore, the pressure produced from HFNC flow rates is much lower in comparison to NIV. 

Woman wearing nasal cannula. Woman wearing oxygen mask. Illustration.

Figure 2. Similar to noninvasive ventilation (NIV), high-flow nasal cannula (HFNC) reduces room air entrapment to allow for more precise oxygen delivery, uses a specialized interface, and can provide respiratory support to patients with hypoxia. Unlike NIV, in HFNC, flow rates are set and less pressure is produced from these flow rates. 


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When should I avoid the use of HFNC?

Do not use high-flow nasal cannula, or HFNC, in patients with:

  • Ventilatory failure
  • Hypercapnia

Woman with blue face. Drop of blood, colored slightly blue, with CO2 label. Illustration

Figure 3. High-flow nasal cannula (HFNC) should not be used for a patient with ventilatory failure and hypercapnia. 

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Recommended reading

  • Dysart, K, Miller, TL, Wolfson, MR, et al. 2009. Research in high flow therapy: mechanisms of action. Respir Med. 103: 1400–1405. PMID: 19467849
  • Frat, JP, Thille, AW, Girault, C, et al. 2015. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med. 372: 2185–2196. PMID: 25981908
  • Hernández, G, Vaquero C, Colinas, L, et al. 2016. Effect of postextubation high-flow nasal cannula vs noninvasive ventilation on reintubation and postextubation respiratory failure in high-risk patients: a randomized clinical trial. JAMA. 316: 1565–1574. PMID: 27706464
  • Hernández, G, Vaquero C, González, P, et al. 2016. Effect of postextubation high-flow nasal cannula vs conventional oxygen therapy on reintubation in low-risk patients: a randomized clinical trial. JAMA. 315: 1354–1361. PMID: 26975498
  • Maggiore, SM, Idone, FA, Vaschetto, R, et al. 2014. Nasal high-flow versus venturi mask oxygen therapy after extubation. Effects of oxygenation, comfort and clinical outcome. Am J Respir Crit Care Med. 190: 282–288. PMID: 25003980
  • Mauri, T, Turrini, C, Eronia, N, et al. 2017. Physiologic effects of high-flow nasal cannula in acute hypoxemic respiratory failure. Am J Respir Crit Care Med. 195: 1207–1215. PMID: 27997805
  • Roca, O, Caralt, B, Messika, J, et al. 2019. An index combining respiratory rate and oxygenation to predict outcome of nasal high-flow therapy. Am J Respir Crit Care Med. 199: 1368–1376. PMID: 30576221
  • Roca, O, Messika, J, Caralt, B, et al. 2016. Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: the utility of the ROX index. J Crit Care. 35: 200–205. PMID: 27481760
  • Sztrymf, B, Messika, J, Bertrand, F, et al. 2011. Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study. Intensive Care Med. 37: 1780–1786. PMID: 21946925