High-Flow Nasal Oxygen for Preoxygenation

Obese patients desaturate rapidly during the apneic period after induction of anesthesia for elective surgery. Administration of oxygen using high-flow nasal cannulae (HFNCs) may prevent desaturation in nonobese patients compared to facemask (FM) preoxygenation. The aim of this meta-analysis was to compare the effectiveness of HFNC to FM preoxygenation techniques in reducing preintubation desaturation in obese patients undergoing elective surgery. This study protocol was registered on PROSPERO (CRD42022309391). Adult studies that compared HFNC and FM preoxygenation in obese patients requiring general anesthesia for elective surgery were included. The primary outcome was desaturation resulting in oxygen saturation of <92% from induction of anesthesia until intubation. Secondary outcomes included the lowest arterial oxygen content before intubation expressed in mm Hg, safe apnea time expressed in seconds, the lowest oxygen saturation before intubation expressed as a percentage, patient-reported discomfort, the need for rescue ventilation, and the incidence of aspiration of gastric contents during intubation. Risk of bias was assessed using the Cochrane Collaboration tool. Certainty was assessed following the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Six studies including 351 participants were eligible for analysis. There was no difference in odds of oxygen desaturation <92% between HFNC and FM (odds ratio [OR], 0.49; 95% confidence interval [CI], 0.15-1.63; P = .24). The HFNC group had a significantly longer safe apnea time (mean difference [MD], -124.20 with 95% CI, -200.47 to -47.93; P = .001). There was no difference between HFNC and FM in the lowest arterial oxygen content (MD, -23.90; 95% CI, -88.64 to 40.85; P = .47) and the lowest peripheral oxygenation saturation (MD, -0.47 with 95% CI, -5.07 to 4.12; P = .84). HFNC had a lower odd of discomfort than FM (OR, 0.13; 95% CI, 0.03-0.52; P = .004). There was no difference in the odds of aspiration of gastric contents between HFNC and FM (OR, 0.33; 95% CI, 0.01-8.21; P = .50). The risk of bias for our primary and secondary outcomes was low. The GRADE assessment for our primary outcome indicated a low level of certainty. For secondary outcomes, the GRADE assessment indicated a very low certainty for all outcomes except for patient discomfort, which was indicated as a moderate level of certainty. There may be no difference between HFNC and FM preoxygenation in preventing oxygen desaturation <92% or the lowest oxygen saturation before intubation. Preparation remains important to prevent and manage desaturation during induction of obese patients.

Current practice guidelines recommend the use of nasal cannula as an alternative pre-oxygenation method for tracheal intubation. However, the efficacy of high-flow nasal oxygenation versus standard facemask oxygenation has not been fully evaluated. We searched PubMed, Cochrane Library, and ClinicalTrials.gov for English-language studies published from January 1, 2000 to November 30, 2021. We included randomized controlled trials which compared high-flow nasal oxygenation and facemask oxygenation as the pre-oxygenation maneuver. Primary outcome was arterial partial pressure of oxygen (PaO2) after pre-oxygenation. Secondary outcomes were safe apnea time, arterial desaturation during intubation, lowest peripheral capillary oxygen saturation during intubation, and patient comfort score. Random-effects models and Mantel-Haenszel method were used for data synthesis. A total of 16 randomized controlled trials and 1148 patients were included. High-flow nasal oxygenation achieved a higher PaO2 compared with facemask, mean difference: 64.86&#x200a;mm Hg (95% confidence interval [CI]: 32.33-97.40, P&#x200a;<&#x200a;.0001). Safe apnea time was longer in high-flow nasal oxygenation, mean difference: 131.03&#x200a;seconds (95% CI: 59.39-202.66, P&#x200a;<&#x200a;.0001). There was no difference in the risk of peri-intubation desaturation or lowest peripheral capillary oxygen saturation between groups. Patient comfort score was higher in high-flow nasal oxygenation, mean difference: 1.00 (95% CI: 0.46-1.54, P&#x200a;=&#x200a;.0003). High-flow nasal oxygenation better enhanced PaO2 and extended safe apnea time and is not inferior to facemask oxygenation in preventing desaturation during tracheal intubation. High-flow nasal oxygenation may be considered as an alternative method, especially for patients with a potential difficult airway.

High-flow nasal oxygen (HFNO) has emerged as a valuable tool in perioperative respiratory management, extending its indications beyond intensive care. By delivering heated and humidified oxygen at high flow rates and a precise fraction of inspired oxygen, HFNO improves oxygenation through physiological mechanisms such as dead space washout, generation of low-level positive airway pressure, and reduction of inspiratory effort. Increasing evidence supports its use during multiple perioperative phases, including preoxygenation and apnoeic oxygenation for airway management, prevention of postoperative hypoxaemia, and respiratory support following major surgery. Compared with conventional oxygen therapy, HFNO prolongs safe apnoea time and decreases the incidence of desaturation, especially in high-risk populations such as obese and cardiothoracic surgical patients. In the postoperative period, it may reduce the need for escalation to non-invasive ventilation and improve patient comfort. Moreover, HFNO enhances safety during procedural sedation, such as endoscopy and bronchoscopy, by limiting hypoxaemic events. However, limitations remain, including variability in flow titration, modest and flow-dependent positive end-expiratory pressure generation, and heterogeneity among clinical studies. Future research should focus on defining optimal patient selection, standardising flow settings, and integrating HFNO into personalised perioperative oxygenation strategies. Overall, HFNO represents a well-tolerated, physiologically sound, and clinically valuable option for oxygen delivery throughout the perioperative continuum.

Obesity is a risk factor for airway-related incidents during anaesthesia. High-flow nasal oxygen has been advocated to improve safety in high-risk groups, but its effectiveness in the obese population is uncertain. This study compared the effect of high-flow nasal oxygen and low-flow facemask oxygen delivery on duration of apnoea in morbidly obese patients. Morbidly obese patients undergoing bariatric surgery were randomly allocated to receive either high-flow nasal (70 L min-1) or facemask (15 L min-1) oxygen. After induction of anaesthesia, the patients were apnoeic for 18 min or until peripheral oxygen saturation decreased to 92%. Eighty patients were studied (41 High-Flow Nasal Oxygen, 39 Facemask). The median apnoea time was 18 min in both the High-Flow Nasal Oxygen (IQR 18-18 min) and the Facemask (inter-quartile range [IQR], 4.1-18 min) groups. Five patients in the High-Flow Nasal Oxygen group and 14 patients in the Facemask group desaturated to 92% within 18 min. The risk of desaturation was significantly lower in the High-Flow Nasal Oxygen group (hazard ratio=0.27; 95% confidence interval [CI], 0.11-0.65; P=0.007). In experienced hands, apnoeic oxygenation is possible in morbidly obese patients, and oxygen desaturation did not occur for 18 min in the majority of patients, whether oxygen delivery was high-flow nasal or low-flow facemask. High-flow nasal oxygen may reduce desaturation risk compared with facemask oxygen. Desaturation risk is a more clinically relevant outcome than duration of apnoea. Individual physiological factors are likely to be the primary determinant of risk rather than method of oxygen delivery. NCT03428256.

High-flow nasal oxygenation (HFNO) has gained popularity in tubeless upper airway surgery owing to its ability to maintain oxygenation during apnoea. We dissect current evidence on HFNO, discuss its limited ventilatory capability, and integrate established guidelines with emerging research to propose practical considerations in its use. Despite early claims of ventilatory benefit, accumulating evidence suggests that HFNO does not clear carbon dioxide. In both adults and children, consistent arterial carbon dioxide accumulation across a wide range of flow rates highlights the risk of hypercapnia. This has important clinical implications for haemodynamic and neurologic function, especially in high-risk populations. Anaesthetists and the scientific community should replace the term 'transnasal humidified rapid-insufflation ventilatory exchange (THRIVE)' with 'apnoeic high-flow nasal oxygenation (apnoeic HFNO)', with an emphasis on multimodal carbon dioxide monitoring the selective use of ventilatory adjuncts when required.

In obese patients, preoxygenation with non-invasive ventilation (NIV) was reported to improve outcomes compared with facemask. In this setting, high-flow nasal cannulae (HFNC) used before and during intubation has never been studied against NIV. The PREOPTIPOP study is a randomised, single-centre, open-labelled, controlled trial including obese patients requiring intubation before scheduled surgery. Patients were randomised to receive preoxygenation by HFNC or NIV. HFNC was maintained throughout intubation whereas NIV was removed when apnea occurred to perform laryngoscopy. The study was designed to assess the superiority of HNFC. The primary outcome was the lowest level of end-tidal oxygen concentration (EtO2) within 2&#x202f;min after intubation. Secondary outcomes included drop in pulse oximetry and complications related to intubation. A total of 100 patients were randomised. The intent-to-treat analysis found median [IQR] lowest EtO2 of 76% [66-82] for HFNC and 88% [82-90] for NIV (mean difference&#x202f;-&#x202f;12&#xb7;1 [-&#xa0;15&#xb7;1 to -&#xa0;8&#xb7;5], p&#x202f;<&#x202f;0&#xb7;0001). Mild desaturation below 95% was more frequent with HFNC (30%) than with NIV (12%) (relative risk 2&#xb7;5, IC 95% [1&#xb7;1 to 5&#xb7;9], p&#x202f;=&#x202f;0&#xb7;03) and median lowest SpO2 during intubation was 98% [93-99] in HFNC vs. 99% [97-100] in NIV (p&#x202f;=&#x202f;0&#xb7;03). Severe and moderate complications were not different but patients reported more discomfort with NIV (28%) vs. HFNC (4%), p&#x202f;=&#x202f;0&#xb7;001. Compared with NIV, preoxygenation with HFNC in obese patients provided lower EtO2 after intubation and a higher rate of desaturation <&#xa0;95%. Institutional funding, additional grant from Fisher & Paykel. Clinical trial Submission: April 10, 2017. Registry name: Preoxygenation Optimization in Obese Patients: High-flow Nasal Cannulae Oxygen Versus Non-invasive Ventilation: A Single-centre Randomised Controlled Study. The PREOPTIPOP Study. Clinicaltrials.gov identifier: NCT03106441 N&#xb0;ID RCB: 2017-A00305-48. Institutional review Board: CPP Nord-Ouest I, registration number 019/2017. URL registry:https://clinicaltrials.gov/ct2/show/NCT03106441.