HFNO addresses the pathophysiology of dyspnoea and acts by reducing the work of breathing, improving mucociliary clearance, reduction in anatomical dead space and providing low-level PEEP of 2-5 cm of water.

In a prospective, phase 2 trial by Ruiz- Garia et al in hospitalized patients in 21 patients with a median survival of 19 days, the use of high flow nasal oxygen provided a signal of benefit with rapid, symptomatic relief and reached the 1 point threshold of improvement on the Borg scale which represents the MCID in breathlessness.

A majority of patients were able to tolerate the intervention and complete the entire duration of the 5-day intervention period.

A small sample-size, single arm design, absence of a comparator and absence of a valid outcome measure are potential drawbacks of the study.

While the use of HFNO might have seen a post-trial normalization after the evidence emerged, follow-up trials have been limited. The requirement of an institutional setting for its provision and ethical challenges in withdrawal of treatment might further complicates its usage. Positioning as a comfort measure for alleviation of distress along with an explicit discussion on goals of care might supports its careful, supervised usage in this setting.

References

Ruiz-García, V., Caballero-Eraso, C., Martín-Sánchez, F. J., García-Cabrera, E., & Gómez-Hoyos, E. (2020). High-flow nasal oxygen for the management of refractory dyspnea in palliative care patients with advanced cancer: A phase II study. Palliative Medicine, 34(9), 1234–1241. https://doi.org/10.1177/0269216320935376

Dysart, K., Miller, T. L., Wolfson, M. R., & Shaffer, T. H. (2009).
Research in high flow therapy: mechanisms of action.
Respiratory Medicine, 103(10), 1400–1405.
https://doi.org/10.1016/j.rmed.2009.04.007

Ruangsomboon, O., Dorongthom, T., Chakorn, T., et al. (2019).
High-flow nasal cannula versus conventional oxygen therapy in relieving dyspnea in emergency palliative patients with do-not-intubate status: A randomized crossover study.
Annals of Emergency Medicine, 74(5), 615–626.
https://doi.org/10.1016/j.annemergmed.2019.09.009

Campbell, M. L., Yarandi, H., & Dove-McFalls, S. (2010).
A systematic review of symptom management in terminal dyspnea.
Journal of Pain and Symptom Management, 39(2), 341–352.
https://doi.org/10.1016/j.jpainsymman.2009.07.008