Humidified Heated High Flow Nasal Prong Oxygen
It has many names and abbreviations a few of which are included below;
Heated and Humidified Oxygen via Nasal Cannula (HHNC)
Humidified Heated High flow Nasal Cannula Oxygen (HFNC) or (HHHFNC)
Humidified High Flow Nasal Prong Oxygen (HHFNPO2)
What is it?
It is a technique to deliver high flow oxygen via large diameter nasal cannula which is humidified and heated.
Flow rates can be given up to 60L/min in adults and 25L/min in children with an oxygen/air blender supplying oxygen at 21-100%.
Oxygen concentration can be titrated by blending the gas mixture or changing the flow rates.
How does it work?
Breathing cool dry gases can produce deleterious effects to the respiratory tract. >6 LPM are not recommended for standard nasal cannula. HFNC delivers gas under optimal humidification conditions which provides comfort and may hypothetically facilitate physiological processes of the respiratory system. (E.g. gas delivery, mucous clearing).
Proposed mechanisms are pharyngeal dead space washout, reducing nasopharyngeal resistance thereby reducing work of breathing, generation of PEEP and an increase in end-inspiratory lung volume.
Who should use it?
There is limited evidence for its use.
In children with bronchiolitis studies have shown positive findings.
In other respiratory conditions there is limited data but it is being increasingly used in patients with respiratory distress in Emergency Departments. E.g. Bronchiolitis, pneumonia, asthma, CF, Chronic lung disease and where Non Invasive Ventilation (NIV) is contraindicated.
It is associated with increased patient comfort and tolerance compared to NIV in adults.
Nasal obstruction eg.choanal atresia, nasal polyps, maxillofacial trauma
Life threatening hypoxia
Foreign body aspiration
Open chest wound
Presence of suspected basal skull fracture
Numerous persistent apnoeic episodes
Local trauma, discomfort and pressure areas around nares
Reduction in positive pressure generated by an open mouth or if leak between cannula and nares
Patients require close monitoring and ongoing care as per the hospital policy guideline.
Benefit should be measured by parameters of effort and efficacy:
Blood Gas analysis
Data suggests that if a benefit is going to be seen this should be evident within 30-60mins
There are several available from local paediatric institutions. Work is in train for use in Adults where there is more variation in terms of what is considered acceptable use. Click on the links below to see what is currently available.
Lee, J, Rehder, K, Lee, W, Cheifetz, I, Turner, D (2013) Use of high flow nasal cannula in critically ill infants, children, and adults: a critical review of the literature, Intensive Care Medicine, vol. 39, p. 247-257.
Ricard, J-D (2012) High flow nasal oxygen in acute respiratory failure, Minerva Anestesiologica, July 2012, p. 836 - 841.