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

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.

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.

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

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.

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 F_IO₂ 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

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