Combined laryngo-bronchoscopy intubation approach in the normal airway scenario: a simulation study on anesthesiology residents

1. Introduction

Endotracheal intubation (ETI) is an essential skill for anesthesiologists but it is practiced also by other healthcare professionals (paramedics, nurses, emergency and intensive care physicians). Indeed, ETI is used not only for provision of general anesthesia, but also in the emergency scenarios where airway control is needed [1].

Experience is essential to master the ETI technique, especially when airway management is performed in difficult scenarios. A part from clinical training (i.e., during residency), learning opportunities regarding ETI are offered by the use of simulation, which aims at increasing operator’s confidence with airway management under both normal and difficult conditions [2]. Moreover, simulation allows familiarization with new devices for airway management, and it has been recently adopted to improve confidence with standard procedures performed under the constraints of wearing personal protective equipment [3].

The direct laryngoscope (DL) remains the most commonly used device for ETI. The DL could be relatively difficult to learn for beginners [4, 5] and proficiency deteriorates over time if DL is not routinely practiced [6]. Alternative devices for airway management are available on the market. In particular, video-laryngoscopes (VLSs) have been developed to improve glottic visualization in patients where conventional DL has proven difficult [7, 8]. Learning curve with VLS could be faster than DL and VLSs may provide greater chances of successful ETI by novice personnel [9, 10, 11, 12, 13, 14]. However, the performances of VLS are largely influenced not only by the operator’s experience but also from the characteristics of the device itself: angle of the VLS blade, presence of a channel for the endotracheal tube (ETT), position of the monitor, etc. Practically, while the visualization of vocal cords is usually improved by VLS, directing the ETT through the vocal cords may be more challenging with these devices [15].

Recently, the simultaneous use of DL (or VLS) with the fiberoptic bronchoscope (FOB)—also known as combined laryngo-bronchoscope intubation (CLBI) approach—has been clinically suggested as alternative technique [16, 17, 18, 19, 20, 21, 22]. With such approach, the DL (or VLS) enables smooth introduction of the FOB in the pharyngeal region; in turn, the FOB allows precise guidance of the ETT through the vocal cords. A simulation study showed good results of CLBI technique performed by experienced anesthesiologists (n = 18) as compared to DL and VLS (McGrath®) in a scenario of difficult airway [23]. Similarly, a smaller simulation study (n = 8) showed that combined use of VLS (Airtraq®) and FOB enables faster ETI in difficult airway scenarios as compared to Airtraq® alone [24]. However, the performances of the CLBI technique in non-experienced hands remain to be investigated in larger samples.

We hypothesized that younger doctors have fast learning curves with FOB and may have good proficiency with CLBI approach already during the first years of training. Therefore, we conducted a simulation study aiming at assessing performances of the CLBI technique in a population of anesthesiology residents, comparing this technique with the other commonly used approaches for airway management and ETI (DL and VLS). We secondarily aimed at acquiring information on the best timing for the introduction of this technique during the anesthesiology training.

2. Materials and methods

This study was designed as a randomized, crossover manikin trial, and conducted between January and February 2022 at the “Cristian Ilardi” Simulation Center of the School of Anaesthesia, Intensive Care and Pain Therapy of the University of Catania.

2.2 Study development

We used the same airway manikin (Larry Intubation Trainer, Armstrong Medical Inc., 575 Knightsbridge Parkway, P.O. Box 700, Lincolnshire, IL 60069-0700). The manikin was set with a normal airway scenario and placed on a rigid table in a lighted room. For each participant, the manikin was positioned at the height of the xiphoid process.

All the residents received a standardized 15-minute teaching on the manikin anatomy, on the study methods and on all the devices of the study (including video demonstrations on the use of these devices). After the teaching session, every participant had 15 minutes to practice ETI with the study devices.

Four devices were studied for ETI, and their sequence followed a randomized order (sealed envelopes). Each participant was not allowed to watch each other in order to avoid any teaching bias. The following four techniques for airway management were tested:

A. DL using a Macintosh laryngoscope blade size 3 (Mercury Medical, Clearwater, FL, USA).

B. VLS with distant monitor (VLS-DM) with Glidescope (Glidescope Verathon Inc. 20001 North Creek Parkway Bothell, WA 98011 USA).

C. VLS with screen on device (VLS-SoD) with the McGrath MAC blade X3 (McGrath; Aircraft Medical Ltd, UK); and.

D. CLBI approach with the same Macintosh DL and the use of a disposable bronchoscope (aScope™ 4 Broncho Regular endoscope, Ambu A/S Baltorpbakken 13 DK-2750 Ballerup, Denmark). As shown in Fig. 1, before attempting the ETI with the FOB, the operator performs a DL and then passes the device to the second operator that has the only duty to hold it in place to facilitate the passage of the FOB in the upper airway region.

Fig. 1.CLBI. A: Direct Laryngoscopy with Macintosh blade; B: Combined laryngo-bronchoscope intubation.

All ETI were performed using a lubricated ETT with a 7.5-mm internal diameter. For the VLS procedures, a semi-rigid stylet was already inserted in the ETT to obtain a hockey-stick shape. A stylet was available on request for the DL. The manikin and the ETT were periodically wetted with a lubricant.

Six independent operators (LLV, SM, FM, FT, GS and FS) carried the study. The same author (LLV) provided the standardized teaching sessions, while the others were in charge of organizing the flow of residents, performing the randomization and assessing performances in terms of success and time.

3. Results

The participants of the study had a mean age of 29.7 ± 3.1 years and 39% were males (n = 37). In particular, we enrolled 33, 27, 12, 11 and 13 residents for the first, second, third, fourth and fifth year of their training, respectively. The population characteristics and their experience with each device are reported in Table 1. Of note, on average there was no experience with the CLBI approach in the overall population. The experience with VLSs was negligible in the junior resident population, whilst 5 to 10 VLS procedures were self-reported on average by the senior residents.

Table 2 describes the performances of each device in terms of SR, cTTI and uTTI. Results are shown for the overall participants, and also for the two subgroups of junior and senior residents. The highest SRs (at 1st, 2nd and 3rd attempt) were found for the DL, followed by VLSs (Glidescope® and McGrath®, respectively); the lowest SRs were recorded for the CLBI approach. Similar findings were observed for the cTTI.

Table 3 shows the analyses conducted comparing performances of devices (cTTI and SR both at 1st and 3rd attempt) in the overall population. All the comparisons yielded significant results for the cTTI and the SR at 1st attempt, with the DL being the best performing device followed in order by Glidescope®, McGrath® and CLBI approach. The SR at the 3rd attempt did not show differences in two analyses only: the comparison between DL and Glidescope®, and the one between McGrath® and CLBI.

Table 4 reports the ease of use and the Cormack-Lehane and POGO scores for all the devices, both for the overall participants and for the subgroups according to their training level.

The sensitivity analyses conducted on uTTI (time recorded for successful intubations not corrected for failures) mostly confirmed the primary results obtained on the cTTI. The only difference was that uTTI was not different between Glidescope® and McGrath® devices (p = 0.10 instead of p = 0.006).

4. Discussion

Our simulation study was conducted in a population of 96 anesthesiology residents at different stage of training. Our main focus was to evaluate the performances of the CLBI approach in a population of residents, gathering also initial information on the best timing for introduction of this technique during the anesthesiology training. Indeed, the CLBI seems a promising method and has been implemented in several reports [16, 17, 27, 28, 29, 30, 31]. From conceptual perspectives, it seems intuitive to combine the advantages of DL/VLS (in terms of visualization of the airways) with the possibility to finely guide the ETT with a FOB. For such reasons, it is not surprising the recent development of new devices aiming at combining these techniques (i.e., Provu Video-stylet®).

In a previous simulation study of difficult airways, the CLBI technique produced interesting results when performed by experienced anesthesiologists. In our study, performances of CLBI approach were investigated in less experienced personnel (residents of anesthesiology), starting from an easier simulation scenario (normal airways). We initially hypothesized that younger doctors may have fast learning curves with FOB and thus may be proficient with the CLBI approach. However, we failed to show advantages in the introduction of this CLBI approach in the early stage of training, and in general results of CLBI methods were inferior to the ones obtained with DL and VLSs. Although it was somewhat expected to find longer cTTI for CLBI in normal airway scenario, we found that SR of CLBI was only 50% at the 1st attempt and increased up to 81% by the 3rd attempt; therefore, roughly one participant in five was not able to perform ETI with this approach after three attempts. Even if our results need external validation, our study suggests that CLBI should be reserved to a more advanced stage of anesthesiology training. Indeed, in the subgroup analyses on cTTI according to the experience, the only significant difference was found for the CLBI approach, where senior residents had significantly faster cTTI than junior ones. Moreover, although not significant, a trend in this direction was seen also for the SR, where senior residents had greater SR by the 3rd attempt with the CLBI approach (92%) as compared to junior trainee (75%, p = 0.06). Thus, our results seem supporting that a greater degree of experience is needed before implementing the CLBI approach. However, it seems not strictly necessary to introduce training on CLBI at late stage of anesthesiology residency for a couple of reasons. First, 14 of the 18 CLBI failures by the 3rd attempt were reported for the first year of training, whilst the remaining 4 were seen for the second (n = 1), third (n = 1) and fourth (n = 2) years of training. Second, when considering the visualization of the vocal cords, results of the CLBI technique were not dissimilar from those of DL and VLSs, suggesting that the main difficulty was advancing the ETT due to absence of skills in manipulation of the tip of the FOB. Therefore, teaching the CLBI approach could be considered relatively early, maybe from the second or the third year of anesthesiology residency, as long as training with FOB has already started. On separate note, it should be considered that CLBI approach could be an intriguing technique for teaching younger residents as this technique allows good supervision during the intubation process, with mentor and resident sharing the same view on the screen. Even though we did not explore this item, a previous study showed that supervisors could more easily teach and assess the success of the novices using the CLBI method [32]. Conversely, DL does not allow simultaneous sharing of the view between resident and teacher, and therefore its teaching could be more complex.

We did not find significant differences in cTTI and SR between categories of residents when assessing performances according to the use of DL and the two VLSs. Nonetheless, as the junior residents had longer median cTTI (and generally lower SR) as compared to senior residents, albeit it is possible that this result is difference was not significant because of due to a relatively low sample size.

Another result deserving comments is that DL was the best performing device, both in term of SR and cTTI. The finding of superiority of DL in our study was mostly expected and likely driven by the greater confidence with DL as compared to the other devices and techniques, as shown by the subjective estimation on the number of procedures performed. In this regards, performances followed the experience of the operators with each device. Considering that visualization of the vocal cords was similar between DL and VLSs, it is likely that VLSs suffered from lower experience in directing the ETT after visualization of the glottis, even though a stylet was inserted in the ETT. The superiority of DL as compared to VLS for novice personnel is not a novel finding. Indeed, Savoldelli et al. [10] found that DL had the shortest TTI as compared to other three VLSs (Airtraq®, Glidescope®, McGrath®). Similarly, Ruetzler et al. [33] showed that in personnel without experience in VLS, the DL had the highest SR and the shortest TTI in the normal airway scenario. Similar findings were reproduced by Eismann et al. [34] that found the highest SR and the lower TTI in DL as compared to VLSs (Storz cMac®, Storz dBlade® and Ambu King Vision®), but their results were reverted in case of difficult airways. However, other studies conducted in personnel with low or no airway experience have found that VLS have similar [35] or better [36, 37] SR and/or TTI as compared to DL. Several aspects may influence these results, ranging from the characteristics of the study population to the difficulty of airway management, from the experience with DL to the characteristics of the VLS used.

There are some strengths and several limitations in our study. The main strength of our study was the relatively large sample size as compared to most of the studies in the simulation setting. Another strength is the precision in the analysis which was conducted with the cTTI, a parameter accounting for previously failed attempts, thus avoiding a hypothetical bias where a device with low SR but short TTI would seem outperforming as compared to devices with longer TTI but greater SR. Of note, other studies have been vague on the way they handled the timing for failed attempts. A third strength of our study was the randomization process in the use of the devices.

There are several limitations in our study. First, it is a single center study that requires external validation. Second, although our population may look somewhat homogeneous (young doctors in training), their experience in the airway management was very variable, as described by the number of estimated procedures they performed with each device. Interestingly, the overall experience with CLBI approach was almost negligible and may explain the relatively low SR by the 3rd attempt. A second session of retraining is planned at 6 to 9 months to evaluate retention of skills. Third, some residents were familiar with the simulator as they join the faculty for advanced cardiac life support and other activities of our simulation center. Fourth, although the role of simulation in the field of airway management cannot be over-emphasized and a recent meta-analysis [38] supports the role of simulation training for advanced airway management in medical education, our study suffers from all the issues related to the simulation setting. In brief, simulation scenarios cannot reproduce the real-life challenges in airway management due to presence of secretions and bleeding (among others), as well as to the emotional stress felt by the operator (i.e., anxiety due to progressive desaturation, ongoing resuscitation, etc.) [14, 39, 40]. Moreover, similarity between manikins and the real anatomy has been questioned both in adult and pediatric settings [41, 42, 43].

5. Conclusions

In a simulation setting of normal airways, residents in anesthesiology had significantly lower success rate and longer time to intubation with the combined laryngo-bronchoscopy approach as compared to direct and video-laryngoscopy. However, most of the failures with combined laryngo-bronchoscopy approach by the 3rd attempt were seen in residents of the first year of training, suggesting that training in this technique may be implemented during the anesthesiology training. The best performances obtained by the direct laryngoscopy reinforce the importance of previous experience with the airway device.

Availability of Data and Materials

The data presented in this study are available on reasonable request from the corresponding author.

Author contributions

LLV, FS and MA—designed the research study. SM, FM, FT and GS—performed the research. FS and AN—analyzed the data. LLV, CS and FL—wrote the manuscript. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

The study received a waiver from the local Ethical Committee (Committee Catania 1—Catania, Italy). All participants gave their written informed consent to participate to the study.

Acknowledgment

Not applicable.

Funding

This research received no external funding.

Conflict of interest

The authors declare no conflict of interest. Filippo Sanfilippo is serving as one of the Editorial Board members of this journal. We declare that Filippo Sanfilippoh had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to CM.