High-flow nasal oxygen (HFNO) is a promising new oxygenation technique for anesthesiologists, as its use in recent years has expanded out of intensive care units and into the perioperative arena. Our institution’s first Optiflow™ (Fisher and Paykel Healthcare Ltd, Auckland, New Zealand) device arrived in our ORs in late September of last year, which coincided with a new ENT surgeon’s arrival and a swarm of challenging laryngeal surgeries on the horizon. In addition to its utility in complex airway surgery, it has been exciting to see how useful HFNO has been in optimizing oxygenation in a variety of different cases and the enthusiasm with which our academic department has adopted it. In this article, we share our experiences with the Optiflow™ device and discuss the benefits, applications, and limitations of HFNO techniques.
Compared to conventional oxygen therapy, HFNO offers several distinct advantages due to its unique physiologic effects (Thorac Soc 2018;15:145-55). In contrast to low-flow nasal cannula, HFNO allows for consistent delivery of high FiO2 to the alveoli because of its ability to provide higher flow rates that exceed a patient’s inspiratory flow, thereby reducing the entrainment of room air (Thorac Soc 2018;15:145-55). HFNO generates low-level continuous positive airway pressure that has a splinting effect on upper-airway tissues and enhances alveolar recruitment (Thorac Soc 2018;15:145-55; Anaesthesia 2015;70:323-9). HFNO also decreases the work of breathing due to flow-dependent flushing of carbon dioxide and reduction in the anatomical dead space (Thorac Soc 2018;15:145-55). Because HFNO delivers heated and fully humidified oxygen, additional benefits include preservation of mucociliary function and avoidance of bronchoconstrictor responses to that of cold and dry air (Eur Respir J 1997;10:2250-4; J Appl Physiol (1985) 1996;81:1739-43; Eur Respir J 1988;1:852-5).
Although HFNO has been used in intensive care units since the early 2000s, it was not until 2015 that Patel and Nouraei described the first use of HFNO to safely extend the apneic window in patients with difficult airways undergoing general anesthesia and laryngological surgery (Anaesthesia 2015;70:323-9). This seminal study shed light on the beneficial effects of HFNO described above in the anesthetic setting and introduced the term Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) to more accurately describe the carbon dioxide clearance that occurs due to gaseous mixing and flushing of dead space (Anaesthesia 2015;70:323-9). Since then, HFNO has been gaining significant attention in the realms of anesthesia for ENT surgery, bronchoscopy, and in the endoscopy suites and beyond. Multiple subsequent publications have described its utility in improving preoxygenation and preventing hypoxemia during rapid sequence intubation, difficult airway management, and procedural sedation (Anesth Analg 2020;131:1102-10; Anaesthesia 2023;78:81-92). Due to the high FiO2 and flow rates typically required, perioperative HFNO is used primarily in adults and children who weigh more than 10 kg.
HFNO systems generally consist of a heated circuit, humidifier, flowmeter, large-bore nasal cannula with head strap, and oxygen pipeline connector (Korean J Anesthesiol 2019;72:527-47). Devices such as Optiflow™ are specifically designed for perioperative use and include features such as a default FiO2 of 1.0, higher flow rates of up to 70 L/min, a CO2 sampling tube, and a simplified setup requiring only two to three minutes (A A Case Rep 2017;9:216-8). Other HFNO brands, such as Armstrong Medical (Coleraine, United Kingdom) and Vapotherm (Exeter, New Hampshire) have similar components.
We initially began utilizing HFNO for difficult airway management in the intraoperative period. Our center’s experience aligns with the findings of a systematic review and meta-analysis by Spence et al., which found that compared to conventional oxygenation, HFNO reduced the risk of oxygen desaturation, increased the minimum oxygen saturation, and increased the safe apnea time (Anesth Analg 2020;131:1102-10). This is particularly useful in a large academic department like ours where we teach anesthesiology residents and other trainees on a daily basis. By safely prolonging apneic time and reducing the risk of desaturation, HFNO enhances patient safety during difficult airway management performed by a trainee and provides an unhurried and calm learning environment. We have found that trainees are more likely to succeed on their first-pass intubation attempt under these circumstances, improving their confidence and reducing airway trauma to the patient from multiple attempts.
Specifically for complex laryngology cases, our experience has also been consistent with the growing body of literature supporting the safety and efficacy of THRIVE during “tubeless” laryngeal surgery (Laryngoscope 2020;130:E874-81; Laryngoscope 2022;132:1061-8). Compared to alternative techniques such as intermittent apnea or jet ventilation, THRIVE provides a still and clear surgical field with a low risk of barotrauma. We recently used THRIVE during microlaryngeal surgery for a patient with posterior glottic stenosis/banding and hypomobile left vocal cord secondary to prolonged intubation for respiratory failure. According to David Bracken, MD, Assistant Professor of Laryngology and Director of the UTMB Voice and Swallow Services, “HFNO/THRIVE allows for shared airway teams to have a greater degree of surgical access and minimize extent of tissue manipulation allowing for improved control and efficient, timely intervention. This often allows for the restoration of airway patency or luminal intubatability in scenarios otherwise at high risk for conversion to anterior neck directed airway securement.”
Additionally, HFNO has been very useful for high-risk patients in our endoscopy suite, where balancing adequate sedation with airway obstruction, apnea, and hypoxia can be especially challenging. A recent systematic review and meta-analysis by Thiruvenkatarajan et al. found that in patients undergoing procedural sedation, HFNO reduced the risk of hypoxemia, increased minimum oxygen saturation, and reduced need for airway maneuvers as compared to conventional oxygenation (Anaesthesia 2023;78:81-92). In our experience, HFNO has enabled us to more safely provide sedation for many high-risk patients without invasive airway instrumentation. Recently, while preparing for an upper endoscopy on a morbidly obese patient, the gastroenterologist was delighted to see us place a HFNO cannula. Pointing to the unobstructed access to the mouth provided by HFNO, he explained that it is much easier to maneuver the endoscope than through a face mask.
Postoperatively, we have also found HFNO beneficial as a “bridge therapy” from the time of extubation to recovery in patients at high-risk for airway obstruction, desaturation, atelectasis, and other postanesthetic pulmonary complications (J Clin Anesth 2020;65:109872). Devices such as the Airvo™ (Fisher and Paykel Healthcare Ltd, Auckland, New Zealand) offer greater portability, making them ideal for use during transport. In addition to improving patient safety, this may also translate to long-term cost savings due to reduced procedure room and recovery room times.
As with any technique, it is important to remember the limitations and safety considerations of HFNO, the most serious of which is fire risk. The Anesthesia Patient Safety Foundation recommends using extreme caution when using HFNO, and there have been at least two airway fires described during awake tracheostomy and intraoral surgery when electrocautery was used in proximity to HFNO (J Anesth Patient Saf Found 2018;33:33-68; Anaesth Rep 2020;8:25-7; Anaesthesia 2017;72:781-3). Further studies are needed to investigate the safety of THRIVE during laser laryngeal surgery, but safe use has been reported by centers using specialized anesthesiology-surgical teams (Otolaryngol Head Neck Surg 2023). Other potential contraindications of HFNO include severe nasal obstruction, epistaxis, recent nasal trauma/surgery, significantly raised intracranial pressure, cerebrospinal fluid leak, and base-of-skull fracture (Anaesth Intensive Care 2018;46:360-7). Lastly, HFNO is less effective in cases of pulmonary shunt and is unlikely to maintain oxygenation in the presence of sustained upper-airway obstruction (Anaesthesia 2023;78:81-92).
In conclusion, our institution’s experience with HFNO has been overwhelmingly positive, and we have found it offers significant benefits in various perioperative settings. HFNO has proven to be a valuable tool in managing challenging airways, tubeless laryngeal surgery, high-risk patients undergoing nonoperating room anesthesia, and as a bridge therapy from extubation to recovery. As anesthesiologists continue to adopt HFNO techniques, it is crucial to recognize its limitations and contraindications to ensure patient safety. Our experience demonstrates the potential of HFNO as a promising and transformative technique in the field of anesthesiology.