Topic outline

  • Mandatory Training Before Use

    Review of the materials below is mandatory before using high flow nasal oxygen during anesthesia care. Log completion of training/attendance using the link at the bottom of this page. 

  • What is HFNO?

    High flow nasal oxygen (HFNO) is a descriptive term for a range of oxygen delivery systems able to carry flow rates of up to 100L/min to the patient via nasal cannula. 

    The benefits of HFNO:

    • Its ability to carry close to 100% oxygen even with elevated inspiratory flow rates
    • By washing out carbon dioxide from the anatomical dead space, it creates an additional oxygen reservoir.
    • The high flow rates generate PEEP which leads to alveolar recruitment, reduced work of breathing and increased end expiratory lung volumes
    • The continuous insufflation can facilitate carbon dioxide removal and limit the expected rise in arterial carbon dioxide levels during apnea.

    Our equipment at the BIDMC:

    • A high rate flow meter capable of delivering 70L/min, which can be connected to the Mindray anesthesia machine or wall outlet.
    • It works in conjunction with our existing nasal cannula or alternate cannula that are supplied with the flowmeter.
    • The circuit is not heated or humidified and cannot blend air into the gas flow, therefore it's suitable for short term use only.

    Indications & Contraindications

     Indications for use:

    1. Optimization of pre-oxygenation prior to induction of general anesthesia
    2. Managing the anticipated difficult airway, used an adjunct to maintain oxygenation and improve carbon dioxide removal during induction
    3. With awake fibreoptic or videolaryngoscopic intubation, particularly for those with existing hypoxia, respiratory failure or critical airway stenosis.
    4. Instituted prior to extubation to reduce risk of immediate respiratory complications in the OR

     Absolute Contraindications

    • High fire risk procedures including use of lasers or diathermy in close proximity to the airway
    • Significant untreated tension pneumothorax
    • Known or suspected skull base fracture, or the presence of a communication between the nasal cavity and intracranial space
    • Complete nasal obstruction
    • Recent functional endoscopic sinus surgery
    • Active epistaxis
    • Prolonged pre-operative or post-operative use without humidification
    • Airway disruption including laryngeal fracture or tracheal rupture

     Relative Contraindications

    • Partial nasal obstruction
    • Contagious pulmonary infections such as active tuberculosis
    • Any contraindication to hyperoxia such as bleomycin usage
    • If indicated for a suspected or known COVID patient, then it should be used in conjunction with appropriate PPE
    • In conjunction with positive pressure ventilation via face mask (see below)

    Bag mask ventilation should NOT be necessary after induction and prior to laryngoscopy. Apnea is well tolerated without desaturation and additional positive pressure ventilation with the mask risks gastric insufflation. This is especially true if high flows are used via the nasal cannula and if the APL valve is set to pressures greater than 5 cmH20.  

  • Preparation & Set-up

    HFNO Preparation

    1. Wear appropriate PPE (N95, surgical face mask, eye protection, scrub cap)
    2. Ensure secure connection with the flowmeter and either the Mindray machine or wall outlet
    3. Inspect the flowmeter for visible cracks
    4. Ensure flow gauge is able to dial up to maximum of 70L/min and deliver O2, without an audible leak
    5. Confirm correct oxygen tubing & nasal cannula for delivery of high flow
    6. Connect oxygen tubing to high flow meter
    7. Standard ASA monitoring should be applied to the patient prior to induction or as per extubation
  • How to use HFNO

    Pre-oxygenation and induction of anesthesia including an anticipated difficult airway 

    Prior to induction:  

    • Apply HFNO nasal cannula to the patient and begin flow at 10L/min 
    • Pre-oxygenate by placing the facemask securely over the patient’s nose and mouth, as tolerated, with the nasal cannula still in place 
    • Ensure the APL valve is open 
    • Confirm readiness for induction of anesthesia as normal, e.g.: target EtO2 


    • Administer induction agents
    • Upon loss of consciousness, flows can then be increased to a maximum of 40L/min
    • Bag mask ventilation should NOT be performed. Apnea will be well tolerated due to the high flow nasal oxygen
    • Maintain high flow settings (max 40L/min) during laryngoscopy
    • Perform intubation and confirm placement of ETT as normal

    Immediately after intubation

    •  Turn off HFNO and consider leaving the nasal cannula in place (for peri-extubation use) 


    Awake fiberoptic intubations for the anticipated difficult airway, including the prevention of hypoxia in cases of critical airway narrowing 

    Prior to induction

    • Perform topicalization as normal 
    • Apply HFNO nasal cannula to the patient and begin flow at 10L/min 
    • Consider increasing flow rate slowly to a maximum of 40L/min, as tolerated by patient.
    • Sedation or analgesia may be required in this setting. 


    •  Perform fibreoptic intubation and confirm placement of ETT as usual 

    Immediately after intubation

    •  Turn off HFNO and consider leaving cannula in place (for peri-extubation use)  

    Extubation planning for known, difficult airways or for patients with a high risk of airway collapse or desaturation soon after extubation. 

    • During emergence: restart flows through nasal cannula, maximum 40L/min 
    • During extubation: keep high flows running through nasal cannula 
    • After extubation: keep high flows running through nasal cannula, wean down flows as able.   
    • Application of the face mask should not be necessary, and positive pressure ventilation risks gastric distension while high flows are being delivered via the nasal cannula. 
    • Wean down flow and assess airway patency prior to moving patient. If unable to wean below 25L/min, then transferring to PACU using HFNO is NOT possible on the transport cylinder. 
    • For transfer to PACU  the maximum setting on O2 transport cylinders is 25L/min  
    • Ensure enough O2 is in the cylinder (size E cylinder: max capacity 680L)
  • Useful Resources

  • Instructional video

    Click on the link below for a brief video demonstration of the following:

    • Setting up the high flow oxygen meter
    • Use of HFNO for the anticipated difficult airway (preoxygenation, fiberoptic intubation,  extubation)
  • References

    General Reviews

    • Ashraf-Kashani N, Kumar R. High-flow nasal oxygen therapy. BJA Educ. 2017;17(2):63-67. doi:10.1093/bjaed/mkw041
    • Cooper J, Griffiths B, Ehrenwerth J. Safe Use of High-Flow Nasal Oxygen (Hfno) With Special Reference to Difficult Airway Management and Fire Risk. APFS Newsl - Off J Anaesth Patient Saf Found. 2018;33(2):33-68.
    • Gleason JM, Christian BR, Barton ED. Nasal cannula apneic oxygenation prevents desaturation during endotracheal intubation: An integrative literature review. West J Emerg Med. 2018;19(2):403-411. doi:10.5811/westjem.2017.12.34699
    • Renda T, Corrado A, Iskandar G, Pelaia G, Abdalla K, Navalesi P. High-flow nasal oxygen therapy in intensive care and anaesthesia. Br J Anaesth. 2018;120(1):18-27. doi:10.1016/j.bja.2017.11.010


    • Spence EA, Rajaleelan W, Wong J, Chung F, Wong DT. The Effectiveness of High-Flow Nasal Oxygen During the Intraoperative Period: A Systematic Review and Meta-analysis. Anesth Analg. 2020;131(4):1102-1110. doi:10.1213/ANE.0000000000005073
    • Wong DT, Dallaire A, Singh KP, et al. High-Flow Nasal Oxygen Improves Safe Apnea Time in Morbidly Obese Patients Undergoing General Anesthesia: A Randomized Controlled Trial. Anesth Analg. 2019;129(4):1130-1136. doi:10.1213/ANE.0000000000003966
    • Piosik ZM, Dirks J, Rasmussen LS, Kristensen CM, Kristensen MS. Exploring the limits of prolonged apnoea with high-flow nasal oxygen: an observational study. Anaesthesia. 2021;76(6):798-804. doi:10.1111/anae.15277
    • Badiger S, John M, Fearnley RA, Ahmad I, Asai T. Optimizing oxygenation and intubation conditions during awake fibre-optic intubation using a high-flow nasal oxygen-delivery system. Br J Anaesth. 2015;115(4):629-632. doi:10.1093/bja/aev262
    • Lyons C, McElwain J, Coughlan MG, et al. Pre‐oxygenation with facemask oxygen vs high‐flow nasal oxygen vs high‐flow nasal oxygen plus mouthpiece: a randomised controlled trial. Anaesthesia. 2022;77(1):40-45. doi:10.1111/anae.15556
    • Lyons C, Callaghan M. Apnoeic oxygenation with high-flow nasal oxygen for laryngeal surgery: a case series. Anaesthesia. 2017;72(11):1379-1387. doi:10.1111/anae.14036


    • Adams TRP, Ricciardelli A. Airway fire during awake tracheostomy using high-flow nasal oxygen. Anaesth Reports. 2020;8(1):25-27. doi:10.1002/ANR3.12038
    • Chang MY, Chen JH, Lin SP, et al. Fire safety study on high-flow nasal oxygen in shared-airway surgeries with diathermy and laser: simulation based on a physical model. J Clin Monit Comput 2021 363. 2021;36(3):649-655. doi:10.1007/S10877-021-00690-4
    • Jermy MC, Spence CJT, Kirton R, et al. Assessment of dispersion of airborne particles of oral/nasal fluid by high flow nasal cannula therapy. PLoS One. 2021;16(2 February):1-13. doi:10.1371/journal.pone.0246123
    • Wilson NM, Marks GB, Eckhardt A, et al. The effect of respiratory activity, non-invasive respiratory support and facemasks on aerosol generation and its relevance to COVID-19. Anaesthesia. 2021;(March):1465-1474. doi:10.1111/anae.15475
    • Sud A, Athanassoglou V, Anderson EM, Scott S. A comparison of gastric gas volumes measured by computed tomography after high-flow nasal oxygen therapy or conventional facemask ventilation. Anaesthesia. 2021;76(9):1184-1189. doi:10.1111/anae.15433
    • Stolady D, Gavula L, Young E, Blunt M, Young P. The Risk of Gastric Insufflation with THRIVE Report of THRIVE-Safe nasal Cannula. Published online 2015.
    • McLellan E, Lam K, Behringer E, et al. High-flow nasal oxygen does not increase the volume of gastric secretions during spontaneous ventilation. Br J Anaesth. 2020;125(1):e75-e80. doi:10.1016/j.bja.2020.02.023
  • Confirmation of Training

    Please log completion of training/attendance using this link: