High flow nasal cannula for adult acute hypoxemic respiratory failure in the ED setting

Abstract

Introduction: High flow nasal cannula (HFNC) is a noninvasive ventilation (NIV) system that has demonstrated promise in the emergency department (ED) setting.

Objective: This narrative review evaluates the utility of HFNC in adult patients with acute hypoxemic respiratory failure in the ED setting.

Discussion: HFNC provides warm (37 °C), humidified (100% relative humidity) oxygen at high flows with a reliable fraction of inspired oxygen (FiO₂). HFNC can improve oxygenation, reduce airway resistance, provide humidified flow that can flush anatomical dead space, and provide a low amount of positive end expiratory pressure. Recent literature has demonstrated efficacy in acute hypoxemic respiratory failure, including pneumonia, acute respiratory distress syndrome (ARDS), coronavirus disease 2019 (COVID-19), interstitial lung disease, immunocompromised states, the peri-intubation state, and palliative care, with reduced need for intubation, length of stay, and mortality in some of these conditions. Individual patient factors play an important role in infection control risks with respect to the use of HFNC in patients with COVID-19. Appropriate personal protective equipment, adherence to hand hygiene, surgical mask placement over the HFNC device, and environmental controls promoting adequate room ventilation are the foundation for protecting healthcare personnel. Frequent reassessment of the patient placed on HFNC is necessary; those with severe end organ dysfunction, thoracoabdominal asynchrony, significantly increased respiratory rate, poor oxygenation despite HFNC, and tachycardia are at increased risk of HFNC failure and need for further intervention.

Conclusions: HFNC demonstrates promise in several conditions requiring respiratory support. Further randomized trials are needed in the ED setting.

Keywords: Acute hypoxemic respiratory failure; COVID-19; High-flow nasal cannula; Noninvasive ventilation.

Fig. 1

An example of a HFNC delivery setup: (A) Pressurized medical air and oxygen is delivered to an air and oxygen blender where (B) the fraction of oxygen is titrated; a flow meter (C) adjusts the flow of the air and oxygen mixture that is delivered to a heater and humidifier (E). An oxygen monitor (D) can be placed in line for a precise measurement of the fraction of “downstream” oxygen; the humidified air and oxygen mixture is delivered to the patient by a special nasal cannula (F).