Why might high-flow nasal cannula (HFNC) therapy fail?

Michael Allison, MD
26th Nov 2020

Just as with noninvasive ventilation (NIV), high-flow nasal cannula (HFNC) is not 100% successful and not indicated in all forms of respiratory disease. Let’s discuss the choice of patients who receive HFNC and how monitoring their response can predict the failure of therapy. 

 

Patient selection

There are two key patient groups in which HFNC should generally be avoided.

  1. Patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD).
  2. Intensive care unit (ICU) patients on vasoactive drips.

Patients with acute exacerbations of chronic obstructive pulmonary disease

These are patients that you know will benefit from the use of NIV. However, the use of HFNC in these patients is much less studied. 

Man with blue face. Illustration.

Figure 1. In patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD), the benefit of using noninvasive ventilation (NIV) is clear. 

High-flow nasal cannula, or HFNC, can be attempted during breaks from NIV, but shouldn’t be considered as a replacement for NIV. 

 

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Intensive care unit patients on vasoactive drips

The next group of patients in which HFNC should generally be avoided is patients who are on vasoactive drips in the intensive care unit. 

Patients who are in shock and require vasopressors have a much higher rate of HFNC failure. Consideration should be made for earlier intubation in these patients.

Woman in hospital bed with IV. Illustration

Figure 2. High-flow nasal cannula (HFNC) should not be used on patients in the intensive care unit (ICU) with vasoactive drips. 

 

Patient monitoring

Now we need to consider the role of monitoring clinical variables after placing patients on high-flow nasal cannula. Let’s say we’ve put our patient with pneumonia on HFNC and they are requiring 50 L of flow and an FIO2 of 60%. How will we know if our patient is likely to fail HFNC therapy?

Indications of possible high-flow nasal cannula failure:

  1. Persistence of thoracoabdominal dyssynchrony 
  2. Increased respiratory rate
  3. Increase in oxygen requirements

That’s it for now. If you want to improve your understanding of key concepts in medicine, and improve your clinical skills, make sure to register for a free trial account, which will give you access to free videos and downloads. We’ll help you make the right decisions for yourself and your patients.

Recommended readings

  • 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 Care35: 200–205. PMID: 27481760