Supraglottic Jet Oxygenation and Ventilation in Fiberoptic Intubation Training for Anesthesia Residents in a Simulated Difficult Airway: A Randomized Controlled Study

Introduction

Effective airway management is a fundamental component of anesthetic practice and plays a critical role in ensuring patient safety, particularly in situations involving difficult airways. Failure to secure the airway promptly and effectively can lead to severe hypoxia, brain injury, or even death, underscoring the importance of meticulous training in airway management techniques for anesthesiology residents [1]. Among various advanced approaches, fiberoptic bronchoscope-guided endotracheal intubation is widely regarded as the gold standard for managing anticipated or simulated difficult airways due to its ability to provide continuous oxygenation and visualization during the procedure [2]. However, this technique demands a high level of manual dexterity and a comprehensive understanding of airway anatomy, which translates into a steep and prolonged learning curve for inexperienced trainees. As a result, novice practitioners often require longer intubation times and may inadvertently prolong apnea periods, thereby increasing the risk of hypoxemia and compromising patient safety during their training [3]. Recent reports indicate that the incidence of difficult airway events ranges from 1.5% to 8.5% in various clinical settings, contributing significantly to anesthesia-related morbidity and mortality [4,5]. Although simulation-based training has been extensively integrated into residency curricula to mitigate these risks, the potential for oxygen desaturation during prolonged intubation attempts remains a critical limitation. This highlights the need for supportive techniques that can extend the safe apnea time and reduce the likelihood of hypoxemia, thereby allowing trainees to develop essential skills in a safer and more effective manner.

Supraglottic jet oxygenation and ventilation (SJOV) is a novel non-invasive oxygenation technique that delivers high-pressure, high-frequency oxygen pulses through a small supraglottic catheter positioned above the vocal cords [6]. By insufflating oxygen directly into the pharyngeal cavity, SJOV enables continuous oxygen delivery and facilitates carbon dioxide washout without obstructing the procedural field. Compared with conventional facemask ventilation, SJOV can maintain higher oxygen reserve and provide more effective support during apnea, making it particularly suitable for scenarios where maintaining airway access and visualization is essential. Previous clinical studies have shown that SJOV can significantly prolong safe apnea time and prevent desaturation in patients with difficult airways or impaired ventilation [7,8]. Despite these advantages, its utility in educational scenarios such as simulation-based fiberoptic intubation training has not been thoroughly investigated.

This study assessed the effectiveness of SJOV in enhancing oxygenation and reducing the incidence of hypoxemia during fiberoptic bronchoscope-guided intubation training in a cervical collar-simulated difficult airway model. We hypothesized that the application of SJOV would improve oxygen reserve, decrease the occurrence of hypoxemia, and facilitate the learning process by enhancing procedural confidence and technical proficiency while minimizing ventilation-related complications among anesthesiology residents. Therefore, we evaluated the use of supraglottic jet oxygenation and ventilation in 25 fiberoptic intubations performed by 20 third-year anesthesia residents.

Material and Methods

STUDY DESIGN AND ETHICS:

This was a prospective, randomized controlled study conducted at Nanjing First Hospital. Ethical approval was obtained from the institutional ethics committee (Approval No. KY20230330-02), and the study was registered with the Chinese Clinical Trial Registry (ChiCTR2300072851). Written informed consent was obtained from all patients or their legal guardians prior to enrollment.

PARTICIPANTS:

Twenty third-year anesthesiology residents undergoing standardized clinical training between July 2023 and January 2025 were recruited. All participants had extensive experience in direct laryngoscopic intubation but no prior exposure to fiberoptic bronchoscopy. Before the study, all residents completed basic training and assessments in oral fiberoptic intubation on mannequins simulating difficult airway scenarios.

Patient inclusion criteria were:

Exclusion criteria were:

RANDOMIZATION:

Twenty third-year anesthesiology residents were randomly assigned to 2 groups using a computer-generated randomization table. The SJOV group (Group S, n=10) received continuous supraglottic jet oxygenation and ventilation with Wei Nasal Jet Tube (Well Lead Medical Co., Ltd., China) during fiberoptic intubation, while the facemask group (Group M, n=10) received standard facemask ventilation, which was removed during fiberoptic intubation. Each resident performed 25 independent oral fiberoptic intubations, resulting in a total of 500 procedures. To simulate a difficult airway scenario, all patients wore a cervical collar (Laerdal™, Copenhagen, Denmark) throughout the intubation process.

ANESTHESIA:

All patients were placed in the supine position and continuously monitored using standard parameters, including electrocardiography (ECG), non-invasive blood pressure (NIBP), peripheral oxygen saturation (SpO₂), bispectral index (BIS), and train-of-four (TOF) stimulation. For preoxygenation, patients received 100% oxygen at a flow rate of 6 L/min via facemask for 3 minutes in a 20° to 25° head-up position. General anesthesia was induced intravenously with midazolam (0.02–0.04 mg/kg), sufentanil (0.5 μg/kg), propofol (1–2 mg/kg), and rocuronium (0.6 mg/kg).

In Group S, a Wei nasal jet tube was inserted nasally to a depth corresponding to the distance from the nostril to the earlobe. Jet ventilation was delivered at 15 pounds per square inch (PSI, 1 PSI=6.895 kPa) with a respiratory rate of 15 breaths/min, an inspiratory-to-expiratory ratio (I: E) of 1: 2, and 100% fraction of inspired oxygen (FiO₂). In Group M, pressure-controlled facemask ventilation was applied with an inspiratory pressure of 15 cmH₂O, respiratory rate of 15 breaths/min, I: E ratio of 1: 2, and 100% FiO₂. In both groups, a manual jaw-thrust maneuver was performed during preoxygenation and induction to maintain upper airway patency. Intubation was initiated once BIS values reached 40 to 60 and TOF was 0. Each resident used a standard 4.5-mm fiberoptic bronchoscope preloaded with a reinforced endotracheal tube (7.5 mm internal diameter for males, 7.0 mm for females). Standing at the head of the bed, the resident advanced the bronchoscope orally through the glottis into the trachea under direct visualization of tracheal rings and carina, followed by advancement of the endotracheal tube to a position 3 to 4 cm above the carina. Intubation success was defined as the confirmation of 2 consecutive end-tidal carbon dioxide (CO₂) waveforms.

Failure was defined as more than 2 intubation attempts, time to intubation exceeding 180 seconds, SpO2 dropping below 90%, or the occurrence of major airway trauma (eg, bleeding or pneumothorax). In cases of failed intubation, the cervical collar was removed and the supervising attending physician completed the intubation using an alternative technique. If SpO2 dropped below 90%, facemask ventilation was resumed until SpO2 reached ≥98%. Difficult airway management was conducted in accordance with the 2022 American Society of Anesthesiologists Difficult Airway Management Guidelines [7].

OUTCOMES:

For each patient, the following baseline airway characteristics were recorded: Mallampati classification, thyromental distance, and inter-incisor distance after cervical collar placement. Intubation outcomes included success or failure and the time required to complete the procedure.

During the training phase, any episodes of oxygen desaturation (SpO₂ <90%) were recorded. The intubation time for each resident was also documented. In addition, ventilation- and intubation-related complications – including nasal bleeding, dental injury, soft tissue trauma, and laryngospasm – were continuously monitored and documented throughout the study.

After completing the training, participants were surveyed to assess their confidence in performing tracheal intubation, learning interest, and satisfaction with the instructors, each measured on a 10-point scale. The study used a dual-dimension assessment system consisting of a modified anesthesia-specialty Mini-Clinical Evaluation Exercise (Mini-CEX) and Directly Observed Procedural Skills (DOPS) to systematically evaluate the residents’ clinical competencies [8].

The Mini-CEX scale focused on 8 core domains: appropriateness of indications, adherence to procedural standards and recognition of key steps, three-dimensional anatomical localization skills, effectiveness of patient–clinician communication, demonstration of humanistic care, overall competency in clinical decision-making, quality of perioperative management, and patient/team satisfaction. The DOPS scale assessed 7 key procedural elements, including completeness of pre-intubation risk assessment, accuracy of specialty-specific physical examination, adequacy of pre-procedural preparation (including equipment check and contingency planning), standardization of technical performance, ability to seek assistance appropriately, demonstration of professionalism (aseptic technique and privacy protection), and overall procedural performance. A modified specialty-specific 9-point rating scale was used for scoring. A score ≤6 on any item was considered unsatisfactory, whereas scores of 7 to 9 were classified as good to excellent. Total scores were calculated based on the number of assessed dimensions: the Mini-CEX contained 8 items with a maximum theoretical score of 72 (8×9), and the DOPS included 7 items with a maximum score of 63 (7×9).

STATISTICAL ANALYSIS:

This randomized controlled study compared SJOV with conventional facemask ventilation regarding 2 primary outcomes: (1) the minimum number of procedures required for resident physicians to achieve competency in fiberoptic-guided tracheal intubation (defined as the learning curve inflection point), and (2) the incidence of peri-intubation hypoxemia. Based on previous studies indicating that residents typically require 15 to 20 procedures to master fiberoptic-guided intubation, each resident was assigned to perform 25 intubation attempts to ensure comprehensive coverage of the learning curve [9].

Sample size calculation was based on the primary outcome measure – the difference in the number of cases at the learning curve inflection point. Preliminary pilot data showed a reduction of 7 procedures at the inflection point in the SJOV group compared to the facemask ventilation group (Δ=7). Using a two-sided significance level of α=0.05 and a statistical power of 1-β=0.8, an independent-samples t test estimated a minimum requirement of 9 residents per group (pilot standard deviation σ=5; Cohen’s d=1.4). Further analysis employing a mixed-effects model to account for the hierarchical structure of repeated measures within trainees, conducted using R software, determined that at least 10 residents per group were required to achieve adequate power.

Learning Curve Analysis: Patients were sequenced chronologically based on the order of intubation completion. Cumulative summation (CUSUM) learning curves were plotted with patients on the x-axis and the CUSUM value on the y-axis. Curve fitting was performed using MATLAB software. The model with the highest coefficient of determination (R²) was selected as the optimal fit, where an R² value closer to 1 indicates a better fit. The curve vertex served as the demarcation point, dividing the learning curve into a learning phase (vertex and prior) and a proficiency phase (post-vertex). The x-coordinate value corresponding to the vertex represents the minimum number of cumulative procedures required to surpass the learning curve inflection point. Non-integer values were rounded up to the nearest integer.

Normally distributed continuous data with homogeneous variance are presented as mean±standard deviation (mean±SD) and compared using the t test. Ordinal data were analyzed using the Mann-Whitney U test. Categorical data are expressed as percentages (%) and compared using Pearson’s chi-square test. A P value <0.05 was considered statistically significant. Data analysis was performed using SPSS 22.0.

Results

BASELINE CHARACTERISTICS:

A total of 20 anesthesiology residents successfully completed 500 fiberoptic intubation procedures, with each resident performing 25 procedures. All data were collected in their entirety with no missing values. There were no statistically significant differences in baseline patient characteristics – including sex, age, BMI, Mallampati classification, thyromental distance, and inter-incisor distance with cervical collar – between the SJOV (Group S) and facemask ventilation (Group M) groups (Table 1).

LEARNING CURVE ANALYSIS:

The overall CUSUM learning curves for both groups were plotted and fitted using third-order polynomial functions.

For Group S, the fitted model was y=0.0443x3 - 3.448x2 + 59.63x – 22.78 (R2=0.99), and the derivative y’=0.1329x2 - 6.896x + 59.63 indicated a peak at x=11, representing the minimum number of procedures required to achieve competency in oral fiberoptic-guided tracheal intubation under the cervical collar-simulated difficult airway model (Figure 1).

For Group M, the fitted model was y=−0.1006x3 + 2.957x2 - 12.97x+59.09 (R2=0.96), and the derivative y’=−0.3018x2 + 5.914x - 12.97 identified a peak at x=18 (Figure 2).

CUSUM analysis showed that Group S reached the peak at 11 cases, whereas Group M peaked at 18 cases, indicating a noticeably faster learning progression in the SJOV group.

OXYGENATION SAFETY:

Regarding oxygenation, no episodes of hypoxemia (SpO2 <90%) occurred in Group S during the learning phase, whereas 25 cases (10%) were recorded in Group M – a statistically significant difference, highlighting SJOV’s protective role in maintaining oxygenation during apneic intubation (Table 2, P<0.001).

INTUBATION TIME AND COMPLICATIONS:

Although statistically significant differences were observed between Group S and Group M in both the Learning period and Plateau period (P<0.001), the absolute differences were small (5.6 s for Learning period and 3.9 s for Plateau period), corresponding to relative differences of approximately 5%. These minor differences, together with small effect sizes (Cohen’s d=0.37 and 0.26, respectively), suggest that the clinical relevance of these findings is limited. No major complications related to intubation or ventilation – such as nasal bleeding, dental injury, soft tissue trauma, or laryngospasm – were observed in any patients.

TRAINEE PERFORMANCE AND FEEDBACK:

Resident feedback indicated significantly greater procedural confidence (P=0.003), interest (P=0.008), and satisfaction (P=0.012) with training in Group S. Objective performance assessed via DOPS was also significantly higher in Group S (Table 3, P=0.01), while Mini-CEX scores showed no significant difference between groups (Table 3, P=0.64), indicating comparable theoretical understanding.

Discussion

In this randomized controlled study, we demonstrated that SJOV significantly improved the efficiency and safety of fiberoptic intubation training among anesthesiology residents in a simulated difficult airway model using a cervical collar. Compared to conventional facemask ventilation, SJOV reduced the number of intubation attempts required to reach procedural competency, decreased the incidence of peri-intubation hypoxemia, and enhanced residents’ technical performance and subjective training satisfaction. These findings provide strong evidence supporting the incorporation of SJOV into fiberoptic intubation training curricula for anesthesia residents [10–12].

CUSUM analysis indicated that residents in the SJOV group achieved procedural competency after approximately 11 cases, compared to 18 cases in the facemask ventilation group, representing a significantly shortened learning curve. This accelerated skill acquisition is particularly valuable in anesthesiology training programs, where procedural efficiency and patient safety are paramount [13,14]. Additionally, no episodes of hypoxemia (SpO2 <90%) occurred in the SJOV group, while the facemask ventilation group had a hypoxemia incidence rate of 10%. Importantly, the SJOV group also achieved higher DOPS scores and reported greater confidence, interest, and satisfaction with the training process. These results suggest that SJOV not only improves physiological outcomes but also enhances the learning experience and procedural confidence of trainees.

Our findings are consistent with previous reports that emphasized the benefits of continuous supraglottic oxygenation in maintaining adequate oxygenation during apneic periods [15,16]. SJOV has been shown to provide effective oxygen delivery in various clinical scenarios, including difficult airway management, awake fiberoptic intubation, and airway procedures in obese or high-risk patients [17]. However, to the best of our knowledge, this is the first study to systematically evaluate the role of SJOV in a simulation-based training setting for anesthesiology residents. Our results demonstrate that SJOV can substantially reduce this learning burden by providing a more stable oxygenation environment, allowing trainees to focus on fiberoptic manipulation and airway anatomy recognition without the urgency imposed by the risk of hypoxemia.

The physiological benefits of SJOV observed in this study are attributable to its capacity to provide high-concentration oxygen jets above the glottis, effectively maintaining alveolar oxygenation even during prolonged apnea periods [18]. By preventing oxygen desaturation, SJOV minimizes the need for emergency ventilation interventions, reduces the stress and time pressure experienced by trainees, and enables a more controlled and deliberate intubation process. This improved oxygen reserve may explain the shorter learning curve and higher procedural confidence reported by residents in the SJOV group.

Although SJOV demonstrated clear benefits in this study, these findings should be interpreted in the context of other supraglottic oxygenation techniques. High-flow nasal oxygen (HFNO) is widely used for apneic oxygenation and has been shown to prolong safe apnea time and reduce hypoxemia. Compared with HFNO, SJOV delivers a focused, high-concentration oxygen jet above the glottis, which can provide more stable oxygenation and relatively better carbon dioxide clearance due to its active jet-driven ventilation. In contrast, CO2 elimination with HFNO is largely passive and can allow progressive CO2 accumulation during complete apnea. Nevertheless, HFNO remains easier to use and may be preferable in patients with unobstructed airways. Further comparative studies in both simulated and clinical settings are needed to clarify the relative advantages of SJOV and HFNO in airway management and training.

Moreover, the higher DOPS scores in the SJOV group indicate that continuous oxygenation facilitated the development of technical skills required for fiberoptic intubation, such as precise scope manipulation and airway structure identification. The comparable Mini-CEX scores between groups suggest that both training methods provided similar levels of theoretical knowledge acquisition, further emphasizing that the primary advantage of SJOV lies in enhancing practical, hands-on skills.

The integration of SJOV into simulation-based fiberoptic intubation training has several important clinical implications. First, by reducing hypoxemia risk and prolonging safe apnea time, SJOV enhances patient safety during resident-performed intubations, particularly in high-risk or difficult airway cases [19]. Second, the accelerated learning curve associated with SJOV may reduce the total number of procedures required for residents to achieve competency, optimizing training efficiency and potentially shortening the duration of airway management rotations [20]. Third, improved resident confidence and satisfaction may lead to greater engagement with airway management training and improved skill retention, ultimately translating into better clinical performance in real-world scenarios. Given the increasing emphasis on simulation-based education in anesthesiology, our findings support the adoption of SJOV as a standard adjunct in fiberoptic intubation training modules, especially for novice trainees.

This study has several limitations that should be acknowledged. First, the single-center design and relatively small sample size limit the generalizability of our findings. Multicenter studies with larger participant cohorts are needed to confirm the reproducibility of these results across diverse training settings. Second, the simulation model employed – a cervical collar to mimic a difficult airway – may not fully replicate the complexity and variability of actual difficult airway scenarios encountered in clinical practice, such as anatomical abnormalities, airway edema, or dynamic obstruction. Importantly, most fiberoptic intubations in clinical practice are performed in non-anesthetized (awake) patients, where physiological conditions and airway dynamics differ from those in our simulation model. Third, all participants were third-year anesthesiology residents with prior experience in direct laryngoscopy but no exposure to fiberoptic bronchoscopy, which may influence the applicability of these results to other trainee populations, including junior residents or non-anesthesiology practitioners. Furthermore, only conventional-frequency SJOV was evaluated in this study. The potential advantages of high-frequency jet ventilation or alternative supraglottic oxygenation techniques, such as high-flow nasal oxygen (HFNO), remain to be explored in the context of simulation-based airway training [21,22]. Additionally, long-term outcomes, such as skill retention and transfer of training effects to clinical practice, were not assessed and warrant further investigation. Future research should focus on validating these findings in multicenter randomized studies involving larger and more diverse trainee populations. Studies comparing SJOV with other oxygenation strategies, such as HFNO, could provide insights into the relative efficacy and safety of different approaches. Longitudinal studies assessing the impact of SJOV-enhanced training on clinical performance, patient outcomes, and complication rates in real-world difficult airway cases are also needed. Finally, exploring the use of SJOV in emergency airway management training and in other high-risk airway procedures may broaden its application and educational value.

Conclusions

Supraglottic jet oxygenation and ventilation (SJOV) enhances the safety and effectiveness of fiberoptic intubation training under simulated difficult airway conditions. In this randomized study, SJOV shortened the number of cases required to achieve procedural competency, eliminated hypoxemia events, and improved trainees’ technical performance, confidence, and satisfaction without increasing complications. These findings support SJOV as a useful adjunct to simulation-based airway management training for anesthesia residents. Further clinical studies are needed to confirm its applicability in real-world difficult airway scenarios.