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Evidence‐based approaches

High‐flow nasal (HFN) oxygen allows delivery of an oxygen concentration of up to 100% at a flow rate of 60 L/min (system dependent). It is an alternative to giving high‐flow oxygen via a reservoir mask in patients with respiratory failure who are not at risk of hypercapnic respiratory failure (O'Driscoll et al. [209]). Because patients with hypoxaemic respiratory failure have greater inspiratory flow requirements, HFN oxygen can meet or exceed the patient's demand while minimizing the risks of air dilution and the inaccurate delivery of oxygen (Nishimura [197], Papazian et al. [212]). Invariably, oxygenation and the work of breathing improve.

Although research on the effects and outcomes of HFN oxygen is limited, several studies have shown that high‐flow oxygen helps to increase alveolar ventilation by flushing out the anatomical dead space of CO₂ (Dysart et al. [69], Nishimura [197]). It also provides low levels of positive end‐expiratory airway pressure (PEEP), which aids alveolar recruitment and reduces atelectasis (Möller et al. [165], Nishimura [197]).

HFN oxygen emulates the temperature and humidity of a healthy adult lung (37°C and 44 mg/L H₂O), providing the physiological benefits of humidification (see the section on humidification below). In addition to increased patient comfort, the nasal cannula allows the patient to eat, drink and communicate freely, increasing compliance (Cuquemelle et al. [53]).

HFN oxygen can be used as a step between conventional oxygen therapy and mechanical ventilation, or as an alternative to non‐invasive ventilation (NIV) (Frat et al. [85], Sztrymf et al. [266]). This may allow the patient to receive care on the ward setting and possibly prevent admission to a high‐dependency or intensive therapy unit. It may also help to wean patients off NIV or mechanical ventilation, and reduce the need for reintubation (Frat et al. [85], Hernández et al. [105]).

High‐flow oxygen can also be delivered via a tracheostomy with an attachment, to give warmed and humidified high‐flow oxygen. However, the other benefits listed above may not apply as no studies have looked at the outcome of using high‐flow oxygen therapy with this patient group.

Rationale

Indications

HFN oxygen is indicated in the following circumstances:

mild to moderate hypoxaemic respiratory failure
difficulty clearing secretions
respiratory wean
cardiogenic pulmonary oedema
symptomatic breathlessness.

Contraindications

There are no documented absolute contraindications to HFN oxygen but relative contraindications may include:

upper gastrointestinal or head and neck surgery and cancers
obstructed nasopharynx
haemoptysis or uncontrolled oral or nasal bleeding
deranged clotting.

Procedure guideline 12.2

High‐flow oxygen therapy

Table 12.8 Prevention and resolution (Procedure guideline 12.2)

Problem	Cause	Prevention	Action
The display shows fluctuating oxygen concentrations	The tubing is water‐logged	Check the tubing at least 4‐hourly.	Hold tubing upright to allow any logged water to flow back into the water chamber.
The patient is unable to tolerate the high flow	High flow of oxygen/air	Explain the rationale for the high flow to the patient as this may aid compliance.	Reduce the flow by 5–10 L/min. Continue to monitor patient's observations, in particular SpO₂, respiratory rate and work of breathing. Escalate any concerns to a senior member of nursing/medical staff.
The patient cannot tolerate the warm oxygen	Warming of gases by the device	Explain to the patient the benefits of warmed oxygen as this may aid compliance.	Consider reducing the temperature if patient is not able to tolerate the oxygen when set at 37°C.
The humidifier/high‐flow system alarms sounds	The nasal cannula has been removed and the HFN oxygen system has been left on	Switch the system off if no longer required.	Replace the nasal cannula on the patient and tighten the straps to ensure a snug fit. Switch the system off if no longer required.
	Part of the system has become disconnected	Check the system set‐up at least 4‐hourly.	Correct any accidental disconnections.
	The bag of sterile water is empty	Replace the bag of sterile water when near empty.	Replace the bag of sterile water.