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Heated and humidified high-flow nasal oxygen in adults: Practical considerations and potential applications

Robert C Hyzy, MD
Section Editor
Scott Manaker, MD, PhD
Deputy Editor
Geraldine Finlay, MD


Oxygen is typically delivered via low-flow systems (eg, nasal cannulae or masks) or high-flow systems (eg, Venturi masks, nonrebreathers). Such conventional systems do not deliver a reliable fraction of inspired oxygen, and are generally poorly tolerated for prolonged periods due to inadequate warming and humidification of inspired gas. While commonly used in infants, the development of newer systems for adults that reliably deliver warmed and humidified oxygen at high flows through nasal cannulae (HFNC) has led to the increasing use of HFNC.

This topic review discusses the practical application and clinical uses of HFNC in adults. Oxygen delivery systems for infants and children are discussed separately. (See "Continuous oxygen delivery systems for infants, children, and adults".)  


The mechanisms by which oxygen delivered via high-flow nasal cannulae (HFNC) offers benefit are shown in the table (table 1) [1]. The major end organ effects are improved comfort and oxygenation. However, whether such effects translate into a meaningful clinical benefit (eg, reduced mortality or intubation rates) is unknown. Mechanisms include:

Small pliable nasal prongs – HFNC nasal prongs are generally soft and pliable. Consequently, several studies have reported improved patient comfort with HFNC when compared with conventional low-flow oxygen delivered through nasal cannulae or high-flow oxygen delivered through a face mask [2-4].

Warming and humidification of secretions – Warming inspired oxygen and heating it to core temperature is more effective at high flow rates (typically >40 L/minute) than low flow rates. Thus, HFNC is better at heating and humidifying inspired oxygen than conventional high-flow systems such as Venturi masks or nonrebreathers (flow rate typically 10 to 15 L/minute) or low-flow systems (flow rates typically <10 L/minute). Increased humidification results in increased water content in mucous, which can facilitate secretion removal and may also decrease the work of breathing and avoid airway desiccation and epithelial injury [5,6].

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Literature review current through: Nov 2017. | This topic last updated: Oct 06, 2017.
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