A 3D-Printed Transoral Guide Device to Aid Single-Person Fiberoptic Intubation: A Randomized Clinical Trial

Introduction

Airway management is a topic of great interest to anesthesiologists, but airway assessment in clinical work is often very subjective, and more than 90% of challenging airway cases are unexpected [1]. If airway management fails, serious complications can ensue, including cardiac arrest, severe hypoxia, and even death [2,3].

For patients with anticipated difficult airways, awake oral or nasal tracheal intubation remains the standard method. However, management of unanticipated difficult airways poses a significant clinical challenge to anesthesiologists, where rapid and secure airway establishment becomes critical to prevent hypoxic complications. Fiberoptic bronchoscopy-guided tracheal intubation is an effective and reliable method for difficult airways in clinical practice. While FOI is a well-established and reliable technique for managing anticipated difficult airways, it is important to note that no robust evidence suggests it is superior to conventional direct laryngoscopy in patients without predicted airway challenges. Its utility in routine practice is therefore not universally advocated.

Fiberoptic intubation through the oral cavity can be questionable for patients with unpredictable difficult airway. In a state of deep sedation or anesthesia, without protective oral reflexes, the soft tissues of the oral cavity (eg, soft palate, tongue, uvula) and epiglottis move back to the posterior wall of the throat, resulting in decreased oropharyngeal space [4]. The fiberoptic bronchoscope is soft and cannot push past this tissue to the exposed glottis to guide endotracheal intubation. To solve this problem, a modified oropharyngeal airway (MOA) device has been reported for use in fiberoptic bronchoscope intubation [5–7], but it has some limitations. First, the front end of the device cannot lift the epiglottis, which often leads to difficulty in passing the fiberoptic bronchoscope through. Second, its use must be combined with jaw thrust [8]. The MOA device requires at least 2 people to complete fiberoptic bronchoscope intubation. Third, the MOA leaves the patient without an oxygen channel, which leads to serious risk for developing hypoxemia in patients with difficult airways. These issues severely limit its use, so we designed a transoral guide device (TGD) to aid fiberoptic intubation.

There have been few studies on how to quickly use fiberoptic bronchoscope to complete oral tracheal intubation under general anesthesia when an unpredictably difficult airway is encountered. Under anesthesia, fiberoptic bronchoscope-guided endotracheal intubation can be completed by a single person, which has not been reported before. Our TGD provides a new method for oral tracheal intubation under fibrobronchoscopy guidance. We assessed the effects of our self-designed fiberoptic bronchoscope oral guide and improved oropharyngeal airway on endotracheal intubation after induction of general anesthesia. This study aimed to evaluate whether the self-designed transoral guide device (TGD) facilitates single-operator fiberoptic intubation without requiring jaw thrust and to compare its performance with the modified oropharyngeal airway (MOA).

Material and Methods

STATISTICAL ANALYSIS:

The sample size calculation for this study was initially based on pilot data (10 patients per group). The primary outcome, first-attempt successful intubation time, was found to be non-normally distributed in the pilot data. Therefore, data are appropriately presented as median and interquartile range (IQR). The TGD group demonstrated a shorter median intubation time compared to the MOA group (30.0 s [IQR: 25.0–35.0 s] versus 34.0 s [IQR: 24.0–58.0 s]). An initial calculation for a Mann-Whitney U test (the non-parametric test chosen for the primary analysis), based on the observed effect size and variability, indicated that a sample size of 32 per group would provide 90% power at a two-sided alpha of 0.05. After accounting for an estimated 10% dropout rate, this yielded a total recruitment target of 72 patients. However, this sample size was expected to yield an unacceptably wide confidence interval around the Hodges-Lehmann estimate of the median difference.

Therefore, a precision-based calculation was performed. The goal was to constrain the width of the 95% confidence interval for the median difference to a clinically acceptable margin. Based on the IQRs from the pilot data, this calculation indicated that a final analyzable sample of 218 patients (109 per group) would be required to achieve this precision. This sample size also comfortably exceeds the requirement for statistical power. Participants were randomly assigned via computerized randomization (SAS 9.4, 1:1 allocation) to evaluate the effectiveness of the device.

Statistical analyses were performed using SPSS software. The normality of distribution for continuous variables was assessed using the Shapiro-Wilk test and visual inspection of Q-Q plots. Normally distributed data are presented as mean±standard deviation (SD), while non-normally distributed data are presented as median with interquartile range (IQR). For categorical variables, data are expressed as frequencies and percentages. Between-group comparisons of normally distributed continuous variables were performed using the independent samples t-test. Non-parametric data were analyzed using the Mann-Whitney U rank sum test. Categorical data were compared using the chi-square test or Fisher exact test. Data on hemodynamic changes were compared using ANOVA. Differences were considered statistically significant at P<0.05.

Results

A total of 305 patients undergoing tracheal intubation for elective surgery from March 2021 to November 2023 were included in the study; 218 patients met the inclusion criteria, with 109 patients in each group. There was no statistically significant difference in the baseline characteristics of the patients in both groups (Table 4).

All 109 patients in the TGD group achieved fiberoptic transoral intubation, and 104/109 patients in the MOA group completed fiberoptic intubation, with a significant difference in the success rates between the 2 groups, at 100% and 95.4%, respectively (P<0.05). The success rate of first-time intubation in the 2 groups was 99.1% and 67%, respectively, with a statistically significant difference of P<0.001. The number of intubation attempts in the TGD group was less than that of the MOA group (Table 5), and the result was statistically significant (P<0.001). The time to successful intubation was 12 seconds faster in the TGD group than in the MOA group (P<0.001). The time to expose the vocal cords was also shorter in the TGD group than in the MOA group (P<0.001). The time to expose the tracheal carina in the TGD group was also shorter than in the MOA group (P<0.001).

The TGD group was superior to the MOA group in both glottic exposure grading and fiberoptic field grading (P<0.001 for both). The VAS score for fiberoptic intubation was significantly higher in the TGD group compared to the MOA group (9 vs 8; P<0.001). There was no statistically significant difference in the incidence of oral mucosal damage, sore throat, and hoarseness between the 2 groups (Table 6). However, there were statistically significant differences in the ease of intubation, intubation resistance and the number of device adjustments. After placing the TGD in the oral cavity, the anterior end of the device could be present in one of 3 positions – A, B and C (Figure 3) – with 22/109 (20.2%) in position A, 54/109 (49.5%) in position B, and 33/109 (30.3%) in position C. Therefore, 69.7% of the patients in the TGD group could be intubated without the need to adjust the position of the device (Table 2). Analysis of variance (ANOVA) showed that hemodynamic changes during tracheal intubation were not significantly different between the 2 groups in terms of mean arterial pressure (MAP) and pulse oximetry (SpO2). The time factor of heart rate (HR) was statistically significant and the fluctuation of heart rate stimulation in the TGD group was smaller than that in the MOA group (Table 7).

Discussion

CLINICAL IMPLICATIONS AND SCOPE OF APPLICATION:

The findings of this study naturally raise the question of the most appropriate clinical role for the TGD device. Based on our results, we propose that the TGD is not intended to replace conventional direct laryngoscopy for routine orotracheal intubation in patients with no predicted airway difficulties. Instead, its primary value lies in the context of fiberoptic intubation (FOI). Specifically, the TGD appears to be an ideal adjunct for patients who require FOI due to an anticipated difficult airway (eg, limited cervical spine mobility, restricted mouth opening, or pathological oropharyngeal conditions). In such patients, it is a true single-operator technique by obviating the need for a dedicated assistant to perform jaw thrust, thereby potentially increasing the efficiency and availability of FOI. Furthermore, its design, which provides a clear and stable conduit, may also make it a valuable rescue option when initial conventional or video laryngoscopy attempts have failed and an unplanned FOI is required. Ultimately, the TGD should be considered a specialized tool to simplify and improve the performance of FOI in selected patients for whom FOI is already indicated.

Conclusions

This study of the use of the self-designed transoral guide device (TGD) in ASA I-III patients undergoing elective surgery without anticipated difficult airways suggests that fiberoptic intubation (FOI) can be successfully completed by a single operator without the need for jaw-thrust maneuver. The findings indicate that the TGD may provide a shorter time to intubation, require fewer intubation attempts, and offer an improved glottic view compared to the MOA. Additionally, it appeared to reduce intubation resistance and ease the intubation process. However, the effectiveness and safety of the TGD in patients with known oropharyngeal pathology, higher ASA physical status (IV-V), or anticipated difficult airways remain to be fully established and require further investigation.

Based on these findings, we propose that the primary clinical role of the TGD is as an adjunct to facilitate single-operator FOI in patients who require fiberoptic intubation due to an anticipated difficult airway. It is not intended to replace conventional laryngoscopy for routine intubation in low-risk patients.