High-flow oxygen therapy (HFOT) is the provision of high-flow, heated and humidified oxygen therapy to the patient through a wide-bore nasal cannula, facemask, tracheostomy mask, or tracheostomy tube.
Evidence-based approaches
igh-flow oxygen therapy allows the accurate delivery of oxygen therapy of up to 100% FiO 2 at a flow rate of up to 60 L/min (system dependent), previously unfeasible via conventional methods of oxygenation (15 L via a non-rebreathable facemask and 6 L via a nasal cannula). Higher flow rates are of particular benefit for patients with hypoxaemic respiratory failure who have greater inspiratory flow requirements. HFOT can meet or exceed the patient’s demand, minimizing the risk of air dilution and the inaccurate delivery of oxygen.
High-flow oxygen therapy emulates the temperature and humidity of a healthy adult lung (37°C and 44 mg/L H 2O), optimizing mucociliary clearance by preserving the function of the ciliated mucosa, reducing the risk of respiratory tract infections and ensuring good oxygenation and ventilation. HFOT also reduces dryness of the upper airway mucosa.
Although research on the effects of HFOT is limited, several studies have shown that high-flow nasal therapy helps to flush out the anatomical dead space, increasing the alveolar ventilation over minute ventilation. It also provides low levels of positive end-expiratory airway pressure which aid alveolar recruitment and reduce atelectasis formation.
The nasal cannula allows the patient to communicate freely and does not interfere with daily activities such as speaking, eating and drinking, thereby increasing patient compliance.
High-flow oxygen therapy can be used as a step between conventional oxygen therapy, non-invasive ventilation or mechanical ventilation, allowing the patient to receive level 2 care on the ward setting and possibly prevent admission to the intensive therapy unit (ITU). It can also help to wean patients off non-invasive or mechanical ventilation, facilitating earlier discharge from the ITU back to the ward.
Indications of High-flow oxygen therapy
• Mild-to-moderate hypoxaemic respiratory failure.
• Difficulty clearing secretions.
• Respiratory wean.
• Symptomatic breathlessness.
Contraindications of High-flow oxygen therapy
There are no documented absolute contraindications 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 High-flow oxygen therapy
Essential equipment
• Drip stand
• Air/O 2 blender
• Oxygen analyser
• Heating equipment
• Water humidification chamber
• Breathing circuit
• High-flow oxygen nasal cannula, mask or tracheostomy attachment
• HME/bacterial filter
• Bag of sterile water
| 1 Assess the patient using patient assessment, vital signs and ABG measurements to decide whether HFOT is indicated. | To determine if the patient is hypoxaemic |
| 2 Explain the principles of HFOT to the patient and family and gain consent. | To increase patient knowledge, minimize anxiety, gain consent and aid patient compliance. |
| 3 Obtain and document patient’s observations prior to commencing HFOT: (a) Respiratory rate (b) SpO2 (c) Heart rate d) Blood pressure (e) Temperature (f) EWS/NEWS | To provide baseline observations prior to commencing oxygen therapy. |
| 4 Ensure patient is sitting upright and in a comfortable position. | To promote comfort and aid lung expansion and breathing. |
| 5 Set up HFOT as per manufacturer’s instructions and attach sterile water bag to water humidification chamber. | Adhering to manufacturer’s guidelines ensures the safe and correct use of equipment. |
| 6 Turn on water humidifier and allow it to reach minimum temperature (37°C). | To warm the water in the chamber. |
| 7 Calibrate oxygen analyser (see Figure 9.7 a) to room air (21%). | To ensure an accurate reading of the oxygen concentration which is to be delivered. |
| 8 Set desired flow rate and oxygen concentration. | To enable the delivery of blended air and oxygen at a high flow. |
| Place the nasal cannula, facemask or tracheostomy attachment onto the patient and tighten the straps. | To ensure the fit is snug and comfortable. Uncomfortable devices will result in poor patient compliance. |
| 9 Monitor vital signs and EWS/NEWS for first 5 minutes after therapy is started. | To detect any deterioration in the patient’s condition. |
| 10 Document the indication for HFOT, the patient’s vital signs, the target oxygen saturation and the set FiO 2and flow rate. | Aim for saturations of 95% for most acutely unwell patients, and 88–92% for those at risk of hypercapnic respiratory failure. To maintain accurate records (NMC 2010 , C) and ensure continuity of care. |
| 12 Continue to monitor and document vital signs and EWS/NEWS at least 4 hourly or more frequently if unstable. | To monitor for signs of deterioration |
| 13 Escalate any problems regarding equipment or patient to an appropriate member of staff (e.g. senior nursing staff , critical care outreach team, medical staff or physiotherapists). | To ensure equipment is working properly. |
| 14 Monitor patient’s response to HFOT and wean flow or oxygen as per senior nursing/medical staff advice. | To reduce oxygen as per patient’s requirements. |
| 15. Check equipment regularly (e.g. 4 hourly) to ensure the correct flow and oxygen concentration are being administered. | To ensure patient is not being over-or under oxygenated. |
| 16: Check tubing regularly to ensure it is free from trapped water. If found, lift tubing and drain water back into the water humidification chamber. | |
| Replace bag of sterile water approximately every 12 hours or as required so that the water humidification chamber does not dry out. | Drying out will cause an increase in the temperature of unhumidifi ed air/oxygen being delivered which may damage the patient’s airway. Drying out of the water chamber may damage equipment. |
Problem Solving, Prevention and resolution of High-flow oxygen therapy
| Problem | Cause | Prevention | Action |
| The oxygen analyser shows fluctuating oxygen concentrations | The oxygen was turned on before the flow during the initial set-up. The tubing is logged with water. | Turn on the flow first, and then increase the oxygen to get the desired oxygen concentration. Check the tubing regularly. | Hold tubing upright to allow any logged water to flow back into the water chamber. |
| The patient is unable to tolerate the high flow of air/oxygen. | Explain the rationale for the high flow to the patient as this may aid compliance | Reduce flow but continue to monitor vital signs, in particular SpO2, respiratory rate and work of breathing. | |
| The patient complains that the air/oxygen is too warm. | Explain to the patient that the air/oxygen will be warm, as this may aid compliance. | Change the humidifier setting from invasive mode to non-invasive mode but only if absolutely necessary as the invasive mode ensures optimal temperature and humidity | |
| The humidifier temperature alarms sounds. | The patient has removed the nasal cannula or mask and the HFOT system has been left on. The temperature/flow probes are not pushed into the circuit properly or have become disconnected. The bag of sterile water has run out. |