Benefits of HFHNC

• Decrease dead space by washing out carbon dioxide with higher flow rates
• Positive end expiratory pressure (PEEP) due to high flow rate increasing nasopharyngeal pressures and decreasing resistance resulting in decreased work of breathing
• More constant fraction of inspired oxygen making oxygen delivery more predictable 
• Humidification for comfort and enabling the high flow rate
• Increased comfort and patient compliance compared to non-invasive positive pressure ventilation (NIPPV)

Indications for HFHNC

• Non-hypercapnic acute hypoxemic respiratory failure (e.g. pneumonia, asthma, pulmonary edema, pulmonary embolism) 
• Pre-intubation and apneic oxygenation due to higher flow rates and FiO2 as compared to regular nasal cannula
• Post-extubation to reduce risk of re-intubation 

How to start HFHNC

1. Set inspiratory fraction of oxygen (FiO2): 0.21 to 1.0
2. Set rate: 2-8 L/min in pediatrics, 16-60 L/min in adults
3. Titrate these settings as needed depending on the response of the patient

HFHNC does not significantly increase tidal volume or PEEP as seen with NIPPV or mechanical ventilation therefore not indicated in hypercarbic patients

Resources: 

• Dysart, Kevin et al. Research in high flow therapy: Mechanisms of action. Respiratory Medicine, Volume 103, Issue 10, 1400-1405. Frat JP, Thille AW, Mercat A, et al; FLORALI Study Group; REVA Network. High-flow oxygen through nasal cannula in acute hypoxemia respiratory failure. N Engl J Med. 2015;372(23):2185-2196.
• Hernández  G, Vaquero  C, González  P,  et al.  Effect of postextubation high-flow nasal cannula vs conventional oxygen therapy on reintubation in low-risk patients: a randomized clinical trial.  JAMA. 2016;315(13):1354-1361.