The Bonfils intubation fibrescope: clinical evaluation and consideration of the learning curve

Endoscopic airway equipment part 2: equipment overview

Endoscopic devices designed for intubation include indirect optical and video laryngoscopes, rigid fibreoptic and video stylets, flexible and rigid bronchoscopes, and optic-enabled intubating supraglottic airways. Various types of surgical operating telescopes can also be used in specific circumstances. It is crucial to understand the strengths and weaknesses of different devices and blade types in order to match the device to the clinical challenge.

The skill of tracheal intubation with rigid scopes - a randomised controlled trial comparing learning curves in 740 intubations

Background

Rigid scopes are successfully used for management of difficult airways, but learning curves have not been established.

Methods

This randomised controlled trial was performed at the University Hospital Bern in Switzerland to establish learning curves for the rigid scopes Bonfils and SensaScope and to assess their performance. Fifteen consultant anaesthetists and 15 anaesthesia registrars performed a total of 740 intubations (10 to 20 intubations with each device per physician) in adult patients without predictors of a difficult airway under general anaesthesia. According to randomisation, physicians intubated the patient’s trachea with either the Bonfils or the SensaScope. A maximum of three intubation attempts was allowed. Primary outcome was overall time to successful intubation. Secondary outcome parameters included first attempt success, first attempt success within 60 s, failures and adverse events.

Results

A clear learning effect was demonstrated: Over 20 trials, intubations became 2.5-times quicker and first attempt intubation success probability increased by 21–28 percentage points. Fourteen and 20 trials were needed with the Bonfils and the SensaScope, respectively, to reach a 90% first attempt success probability. Intubation times were 23% longer (geometric mean ratio 1.23, 95% confidence interval 1.12–1.36, p < 0.001) and first attempt success was less likely (odds ratio 0.64, 95% confidence interval 0.45–0.92, p = 0.016) with the SensaScope. Consultants showed a tendency for a better first attempt success compared to registrars. Overall, 23 intubations (10 Bonfils, 13 SensaScope) failed. Adverse events were rare and did not differ between devices.

Conclusions

A clear learning effect was demonstrated for both rigid scopes. Fourteen intubations with the Bonfils and 20 intubations with the SensaScope were required to reach a 90% first attempt success probability. Learning of the technique seemed more complex with the SensaScope compared to the Bonfils.

Trial registration

Current Controlled Trials, ISRCTN14429285. Registered 28 September 2011, retrospectively registered.

Learning Curves for Two Fiberscopes in Simulated Difficult Airway Scenario With Cumulative Sum Method

INTRODUCTION

The aims of this randomized prospective mannequin study were to determine the amount of attempts required for successful intubation using different fiberscopes (Bonfils and SensaScope) by inexperienced anesthesiologists in a difficult airway scenario and to build the associated learning curves.

METHODS

Difficult airway simulation was achieved with tongue edema in mannequin. After approval of volunteers, we asked 15 anesthesiology residents without any experience with fiberscopes to intubate with each device in a random order. Intubation success (endotracheal intubation within 120 seconds), the degree of difficulty of intubation, and reality of simulation using a 10-point scale were recorded. Learning curves were generated with cumulative sum method.

RESULTS

With Bonfils, 13 volunteers were able to pass lower decision boundary with a median number of 26 [95% confidence interval (CI) = 21.4-25.9] attempts, whereas in SensaScope, the same outcome was observed in 10 residents with a median number of attempts of 26 (95% CI = 23.5-32.5). Total success rate was found significantly higher with Bonfils compared with SensaScope (550/600 vs 512/600, respectively, P < 0.001). Intubation with Bonfils was considered as less difficult compared with SensaScope [median = 4 (95% CI = 3.32-4.42) and 6 (95% CI = 4.96-6.64), P = 0.01, respectively]. The reality of the simulation was rated as a median of 5 (95% CI = 4.37-5.8).

CONCLUSIONS

Although a similar number of attempts were required to reach predetermined competency for both fiberscopes, only 10 of residents were able to obtain the targeted success using SensaScope as compared with 13 with Bonfils. Inexperienced residents found intubation via Bonfils less difficult than SensaScope. High individual variability in obtaining competency observed in this study with cumulative sum analysis underlines the importance of defining success a priori to simulation, the need for follow-up of individual progress, and the need to offer adequate trials to achieve competency. Therefore, learning opportunities should be adapted accordingly.

Difficult airway intubation simulation using Bonfils fiberscope and rigid fiberscope for surgical training

INTRODUCTION

Pediatric otolaryngologists are frequently called to assist in difficult airway management in newborns with Pierre Robin Sequence (PRS) who have microretrognathia, glossoptosis, and an anterior larynx. The Bonfils fiberscope (BF) is a curved rigid scope designed to provide superior visualization in the anterior larynx.

OBJECTIVE

(1) to assess whether BF provides an improvement in intubation success rate, time to intubation, or airway visualization as compared to rigid fiberscope (RF) in a difficult airway simulation setting and (2) to determine whether a training program for BF can improve time to intubation through practice trials.

METHODS

Six right-handed trainees completed five trials on each of the three following airway models using the BF and RF: normal anatomy, anterior larynx and PRS. The normal larynx model was intubated only with RF. Main outcome measures were the time needed for tracheal intubation and Cormack-Lehane classification (1-4).

RESULTS

The majority of the intubation trials showed a statistically significant difference between first and last completion times (p < .05) suggesting construct validity. Only the anterior larynx trials with BF did not demonstrate an improvement in time to intubation between first and last attempts (p < .3125). For the PRS retrognathia model, there was no statistically significant difference in time to intubation between using the BF and the RF (p < .44); in the anterior larynx model, the RF yielded a faster time to intubation than the BF on the final trial attempts (p < .0313). By Cormack-Lehane classification measures, laryngeal visualization by the BF was better than RF in the PRS manikin (p < .0022) while there was no significant difference in grade scores for the anterior larynx manikin (p < .45). All six trainees reported an improved visualization of the larynx with the BF compared to the RF for both the anterior larynx and PRS manikins; at the end of the trial runs, all participants noted an improvement in comfort level using the BF.

CONCLUSION

The difficult airway simulation model is feasible for surgical training. BF adds superior visualization of the anterior larynx in PRS. Otolaryngology training programs may include BF as a supplemental tool in addition to RF as a part of the airway equipment training since there is significant improvement in time to intubation with consecutive practice trials and superior laryngeal visualization.

Predictors of Difficult Intubation with the Bonfils Rigid Fiberscope

BACKGROUND

Endotracheal intubation is commonly performed via direct laryngoscopy (DL). However, in certain patients, DL may be difficult or impossible. The Bonfils Rigid Fiberscope® (BRF) is an alternative intubation device, the design of which raises the question of whether factors that predict difficult DL also predict difficult BRF. We undertook this study to determine which demographic, morphologic, and morphometric factors predict difficult intubation with the BRF.

METHODS

Four hundred adult patients scheduled for elective surgery were recruited. Patients were excluded if awake intubation, rapid sequence induction, or induction without neuromuscular blocking agents was planned. Data were recorded, including age, sex, weight, height, American Society of Anesthesiologist classification, history of snoring and sleep apnea, Mallampati class, upper lip bite test score, interincisor, thyromental and sternothyroid distances, manubriomental distances in flexion and extension, neck circumference, maximal neck flexion and extension, neck skinfold thickness at the cricoid cartilage, and Cormack and Lehane grade obtained via DL after paralysis was confirmed. Quality of glottic visualization (good or poor), as well as the number of intubation attempts and time to successful intubation with the BRF, was noted. Univariate analyses were performed to evaluate the association between patient characteristics and time required for intubation. Variables that exhibited a significant correlation were included in a multivariate analysis using a standard least squares model. A P < 0.05 was considered significant.

RESULTS

Glottic visualization with the BRF was good in 396 of 400 (99%) cases. On the first attempt, 390 patients were successfully intubated with the BRF; 6 patients required >1 attempt; 4 patients could not be intubated by using the BRF alone. These 4 patients were intubated by using a combination of DL and BRF (2 patients), DL and a Frova bougie (1 patient), and DL and an endotracheal tube shaped with a semirigid stylet (1 patient). Mean time for successful intubation was 26 ± 13 seconds. Multivariate analysis showed that decreased mouth opening (P = 0.008), increased body mass index (P = 0.011), and higher Cormack and Lehane grade (P = 0.038) predicted longer intubation times, whereas shorter thyromental distance predicted slightly shorter intubation times (P < 0.0001).

CONCLUSIONS

Mouth opening, body mass index, and high Cormack and Lehane grade predict longer intubation times, as with DL. Decreasing thyromental distance predicts slightly shorter intubation times with the BRF, possibly because of a design initially optimized for a pediatric population with receding chins. These findings, along with the high success rate of BRF in this study, and the possibility of further increasing success rates by combining BRF with DL, help define the role of BRF intubation in contemporary airway management.

A comparison of the transillumination-assisted technique versus midline approach technique in novices: a prospective randomized controlled trial about the Bonfils intubation fiberscope

Background

The present study aimed to compare the safety and efficacy for novices to conduct intubation with the Bonfils intubation fiberscope (BIF) using the transillumination-assisted or midline approach technique in patients with normal airways.

Methods

In this prospective randomized control study, 10 trainees were assigned to the transillumination-assisted technique group (T group) or the midline approach technique group (R group). Each trainee was required to conduct intubation in 50 patients. The primary outcome was intubation time. The secondary outcomes were success rate (%), number of attempts, and complications.

Results

Among the cases of successful intubation, the intubation time was not significantly different between the two groups (P > 0.05). The overall success rate of intubation was not significantly different between the two groups (P > 0.05). The intubation success rates at the first, second, and third attempts as well as the average intubation times were similar between the two groups (P > 0.05), but in patients receiving successful intubation at the second attempt, the intubation time was longer in the T group (P = 0.0006). The incidences of dry throat, sore throat, and hoarseness were higher in the T group (all P < 0.05).

Conclusions

For patients with a normal airway, the transillumination-assisted technique was unlikely to increase the success rate of intubation with the BIF compared with the midline approach technique, but led to more complications.

Trial registration

ChiCTR-INR-16009967, retrospectively registered on November 22, 2016

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-017-0322-6) contains supplementary material, which is available to authorized users.

Awake tracheal intubation in a patient with a supraglottic mass with the Bonfils fibrescope after failed attempts with a flexible fibrescope

Awake intubation with a flexible fibrescope is usually done electively in patients with a known difficult airway. Herein, we describe the case of an elective awake tracheal intubation that was performed on a patient with a large, obstructive supraglottic mass. The intubation was successfully performed using the Bonfils fibrescope after several failed attempts with a flexible fibrescope. This case highlights the usefulness of the Bonfils fibrescope and the limitations of the flexible fibrescope in certain clinical situations.

Endotracheal intubation by inexperienced trainees using the Clarus Video System: learning curve and orodental trauma perspectives

BACKGROUND

The ideal alternative airway device should be intuitive to use, yielding proficiency after only a few trials. The Clarus Video System (CVS) is a novel optical stylet with a semi-rigid tip; however, the learning curve and associated orodental trauma are poorly understood.

METHODS

Two novice practitioners with no CVS experience performed 30 intubations each. Each trial was divided into learning (first 10 intubations) and standard phases (remaining 20 intubations). Total time to achieve successful intubation, number of intubation attempts, ease of use, and orodental trauma were recorded.

RESULTS

Intubation was successful in all patients. In 51 patients (85%), intubation was accomplished in the first attempt. Nine patients required two or three intubation attempts; six were with the first 10 patients. Learning and standard phases differed significantly in terms of success at first attempt, number of attempts, and intubation time (70% vs. 93%, 1.4 ± 0.7 vs. 1.1 ± 0.3, and 71.4 ± 92.3 s vs. 24.6 ± 21.9 s, respectively). The first five patients required longer intubation times than the subsequent five patients (106.8 ± 120.3 s vs. 36.0 ± 26.8 s); however, the number of attempts was similar. Sequential subgroups of five patients in the standard phase did not differ in the number of attempts or intubation time. Dental trauma, lip laceration, or mucosal bleeding were absent.

CONCLUSIONS

Ten intubations are sufficient to learn CVS utilization properly without causing any orodental trauma. A relatively small number of experiences are required in the learning curve compared with other devices.

A systematic review of the role of videolaryngoscopy in successful orotracheal intubation

BACKGROUND

The purpose of our study was to organize the literature regarding the efficacy of modern videolaryngoscopes in oral endotracheal intubation, then perform a quality assessment according to recommended external criteria and make recommendations for use.

METHODS

Inclusion criteria included devices with recent studies of human subjects. A total of 980 articles were returned in the initial search and 65 additional items were identified using cited references. After exclusion of articles failing to meet study criteria, 77 articles remained. Data were extracted according to the rate of successful intubation and improvement of glottic view compared with direct laryngoscopy. Studies were classified according to whether they primarily examined subjects with normal airways, possessing risk factors for difficult direct laryngoscopy, or following difficult or failed direct laryngoscopy.

RESULTS

The evidence of efficacy for videolaryngoscopy in the difficult airway is limited. What evidence exists is both randomized prospective and observational in nature, requiring a scheme that evaluates both forms and allows recommendations to be made.

CONCLUSIONS

In patients at higher risk of difficult laryngoscopy we recommend the use of the Airtraq, CTrach, GlideScope, Pentax AWS and V-MAC to achieve successful intubation. In difficult direct laryngoscopy (C&L >/= 3) we cautiously recommend the use of the Airtraq, Bonfils, Bullard, CTrach, GlideScope, and Pentax AWS, by an operator with reasonable prior experience, to achieve successful intubation when used in accordance with the ASA practice guidelines for management of the difficult airway. There is additional evidence to support the use of the Airtraq, Bonfils, CTrach, GlideScope, McGrath, and Pentax AWS following failed intubation via direct laryngoscopy to achieve successful intubation. Future investigation would benefit from precise qualification of the subjects under study, and an improvement in overall methodology to include randomization and blinding.

A randomised comparison of InnoScope and Macintosh laryngoscope in simulated difficult tracheal intubation in manikins

We conducted a crossover randomised study to evaluate the performance of a novel optical stylet, the InnoScope, for tracheal intubation in simulated normal and difficult airways. Twenty-five anaesthetists attempted tracheal intubation on a SimMan 3G simulator using the InnoScope first followed by the Macintosh laryngoscope or vice versa. Three airway scenarios were tested: (1) normal airway; (2) difficult airway with swollen pharynx; and (3) limited neck movement. In each scenario, the laryngeal view, duration of and success rate for tracheal intubation were recorded. Compared with the Macintosh laryngoscope, the use of InnoScope increased the percentage of glottic opening seen by 17% in normal airway, 23% in the difficult airway and 32% with limited neck movement, p < 0.01. Despite this better laryngeal view, successful tracheal intubation achieved with the InnoScope (88.0%) was lower than that for the Macintosh laryngoscope (98.7%), p = 0.008. Using the InnoScope, tracheal intubation during the first attempt was only successful in 48% of cases with difficult airway. In this scenario, the median (interquartile range [range]) duration of tracheal intubation was significantly longer with [corrected] InnoScope compared with the Macintosh laryngoscope, (70 (19-120 [15-120)] s vs 30 [21-58 (15-120)] s, [corrected] p = 0.01. We conclude that an improved laryngeal view with the use of the InnoScope did not translate into better conditions for tracheal intubation.

A comparison of hemodynamic changes after endotracheal intubation by the Optiscope™ and the conventional laryngoscope

Background

Optiscope™ is a newly developed video stylet device. This study evaluated and compared the hemodynamic changes observed after endotracheal intubation with video stylet and after conventional laryngoscopic endotracheal intubation.

Methods

Fifty-eight adult patients with American Society of Anesthesiologists (ASA) physical status class 1 or 2, undergoing general anesthesia, were randomized into two groups: one group of patients were intubated using video stylet (n = 29) and the other group were intubated using direct laryngoscope (n = 29). Systolic blood pressure (SBP), mean arterial pressure (MAP), diastolic blood pressure (DBP), heart rate (HR), POGO (percentage of glottic opening) score, time for intubation and degree of sore throat were recorded.

Results

There were no significant differences in the SBP, MAP, DBP, HR, and the sore throat incidence between the two groups. Optiscope™ produced better POGO scores, but time for intubation was longer than with conventional laryngoscope.

Conclusions

Optiscope™, when compared with conventional laryngoscope for intubation, does not modify the hemodynamic response, but it provides a better view of the vocal cords.

Transillumination-assisted orotracheal intubation: a comparison of the Bonfils fibrescope and the lightwand (Trachlight)

BACKGROUND

Because the Bonfils fibrescope has a semi-rigid optical stylet and is similar in shape to a lightwand, we aimed to evaluate and compare the efficacy of transillumination-assisted orotracheal intubation with the Bonfils fibrescope and the Trachlight(TM) lightwand in patients with normal airways.

METHODS

As a preliminary investigation to form a basis for later studies, therefore, we performed a randomized, single-blind study of 300 patients with normal airways to compare the efficiency of Trachlight and transillumination-assisted Bonfils orotracheal intubation in these patients. In both groups, orotracheal intubation was performed using a transillumination technique. The first attempt and overall success rates of tracheal intubation, the times required, and any untoward effects were recorded.

RESULTS

Although the overall success rates were similar for Bonfils and Trachlight intubations (97.3% and 98.7%, respectively), tracheal intubation was successful on the first attempt in 87.3% of patients with the Bonfils fibrescope compared with 95.3% of patients with the Trachlight (P < 0.05). The mean intubation time for the first attempt was 15 ± 5 s with the Bonfils fibrescope and 9 ± 2 s with the Trachlight (P < 0.001). Patients intubated using the Bonfils fibrescope also experienced significantly more sore throat and hoarseness than those intubated using the Trachlight.

CONCLUSIONS

For patients with normal airways, the Trachlight is superior for orotracheal intubation with respect to reliability, rapidity, and safety compared with the Bonfils fibrescope used with the transillumination technique.

Comparison of the Bonfils and Levitan optical stylets for tracheal intubation: a clinical study

The Bonfils and Levitan FPS scopes are rigid fibreoptic stylets that may assist routine or difficult intubation. This study compared the effectiveness of each in patients with predicted normal airways when used by specialist anaesthetists with no prior experience using optical stylets. Twelve anaesthetists and 324 elective surgical patients participated. Six anaesthetists were randomised to first intubate 20 patients with the Levitan scope (Phase 1) followed by a further seven patients with the Bonfils scope (Phase 2). The other six participating anaesthetists undertook their first 20 intubations with the Bonfils (Phase 1), followed by seven intubations with the Levitan (Phase 2). Outcomes recorded were success rate, total time to intubation, number of attempts, ease of intubation score and incidence of complications. Overall failure rates were similar for the two scopes with 5.6% of patients not intubated after three attempts. Median total times to intubation were similar for the Levitan (44 seconds) and Bonfils (36 seconds) (P = 0.11). Participants using the Bonfils in Phase 1 had significantly higher chance of success on first attempt (73%) compared to Levitan users during Phase 1 (57%) (P = 0.008). These differences were not significant in the second phase and ease of intubation scores were similar for both scopes (P = 0.9). This study showed the two scopes were comparable but the high failure rate amongst novice users demonstrated the importance of familiarity and skill development prior to their introduction to a difficult airway cart.

Improving rigid fiberoptic intubation: a comparison of the Bonfils Intubating Fiberscope with a novel modification

Background

The Bonfils intubating fiberscope has a limited upward tip angle of 40° and requires retromolar entry into the hypopharynx. These factors may make its use less desirable when managing the difficult airway because most anesthesia providers are well versed in midline oral intubation rather than the lateral retromolar approach. The Center for Advanced Technology and Telemedicine at the University of Nebraska Medical Center has developed a novel fiberscope with a more anterior 60° curve to allow for easier midline insertion and intubation. The objective of this work was to evaluate the novel fiberscope, in comparison to the Bonfils intubating fiberscope, in terms of use and function in difficult airway intubation.

Methods

Twenty-two anesthesia providers participated in simulated intubations of a difficult airway mannequin to compare the Bonfils intubating fiberscope with the novel curved Boedeker intubating fiberscope. The intubations were assessed based upon the following variables: recorded Cormack Lehane airway scores, requests for cricoid pressure, time to intubation, number of intubation attempts and success or failure of the procedure.

Results

Participants using the Bonfils fiberscope recorded an average Cormack Lehane (CL) airway score of 1.67 ± 1.02 (median = 1); with the novel fiberscope, the recorded average airway grade improved to 1.18 ± 0.50 (median = 1). The difference in airway scores was not statistically significant (p = 0.34; Fishers Exact Test comparing CL grades 1&2 vs. 3&4). There was, however, a statistically significant difference in intubation success rates between the two devices. With the Bonfils fiberscope, 68% (15/22) of participants were successful in intubation compared to a 100% success rate in intubation with the novel fiberscope (22/22) (p = 0.008). After the intubation trial, the majority of participants (95%) indicated a preference for the novel fiberscope (n = 20).

Conclusions

With this data, we can infer that the novel fiberscope curvature appears to improve or maintain the quality of an intubation attempt (airway score, cricoid pressure requirement, intubation time, number of attempts, placement success). The data indicate that the novel fiberscope offers a superior intubation experience to currently available best practices. The instrument was well received and would be welcomed by most study participants should the device become clinically available in the future.