A difficult airway is defined as the clinical situation in which a conventionally trained anesthesiologist experiences difficulty with facemask ventilation of the upper airway, difficulty with tracheal intubation, or both.1 The difficult airway is a complex interaction among patient factors, the clinical setting, and the skills of the practitioner. It is a feared anesthetic scenario because if handled poorly, hypoxic brain injury or death may result. With the introduction of modern respiratory monitoring in the mid-1980s, and adoption of new standards of care for patient monitoring as well as practice guidelines for management of the difficult airway in 1993, death and brain damage have declined significantly.2 Development of new airway devices may further improve patient safety.
Management of the difficult airway starts with careful patient evaluation, as well as consideration of the relative merits and feasibility of the basic airway management options.3 These include awake tracheal intubation, the invasive technique of securing the airway and/or the preservation of spontaneous ventilation for the primary management plan, and a backup plan should the primary plan fail. Recommended techniques for intubation of the difficult airway include fiberoptic intubation, intubating stylet, and Intubating Laryngeal Mask Airway. Newer intubating devices such as videolaryngoscopes, optic laryngoscopes, and fiberoptic intubating stylets, will broaden the options considerably.4
The main advantage of the conventional intubation devices, such as the Macintosh laryngoscope and fiberoptic bronchoscope (FOB), over the newer devices, is anesthesiologists' familiarity with their use. The Macintosh laryngoscope continues to be the primary choice for routine airway management for most clinicians, and awake, fiberoptic intubation is an option for the anticipated difficult airway. Hence, this equipment is more likely to be available for the trainees' practice. However, direct laryngoscopy may fail in 1.5% to 8.5% of the population despite appropriate operator experience, and adequate patient positioning and mouth opening.5 Difficult intubation occurs with a similar incidence.
The clinical value of bedside screening tests for predicting difficult intubation remains limited. Screening tests such as the Mallampati oropharyngeal classification, thyromental distance, sternomental distance, mouth opening, and Wilson risk score yield sensitivity of 20% to 62% and specificity 82% to 97%.6,7 In addition, direct laryngoscopy may cause significant hemodynamic disturbance, sore throat, airway injury, and dental damage, the latter accounting for one-third of all confirmed or potential anesthetic claims in the United Kingdom.8 Potentially, such injuries may be reduced by a different intubation technique.
Use of the Bonfils Retromolar Intubation Fiberscope (Karl Storz GmbH, Tuttlingen, Germany) shown in Figure 1 was first described by Bonfils in 1983 using a retromolar approach to intubate tracheas of children with Pierre Robin syndrome.9 These children had micro- and retrognathia of the lower jaws, which resulted in serious difficulties during endotracheal intubation. Since its invention 3 decades ago, the Bonfils has proved to be a useful intubation device and its application has widened considerably.10 The Bonfils fiberscope has been reported to be useful in adult and pediatric difficult airways, awake intubation, double-lumen tube (DLT) insertion, percutaneous tracheostomy, and preclinical use. This review gives an overview of its development and summarizes studies reporting its use.
All articles available on MEDLINE and Google were found using the keywords “Bonfils,“ “intubation,” “fiberoptic scope,” “videolaryngoscope,” and “difficult intubation.” References of selected articles were also reviewed. All relevant retrieved articles were selected for inclusion and reference if they were published in a peer-reviewed medical journal.
The Bonfils Design
The Bonfils Retromolar Intubation Fiberscope is a rigid, straight fiberoptic device with a 40-degree curved tip. It is 40 cm long and 5 mm in outside diameter (OD). The 40-degree angle permits targeted intubation. The 110-degree angle of view ensures the necessary overview. It has a handle on which an eyepiece is mounted at the proximal end; the eyepiece is used for direct viewing or can be attached to a camera and video monitor system. A light source or a small battery handle can be attached to the stylet handle.
The adult version of the Bonfils has a 1.2-mm working channel within the shaft, which may be used to perform awake intubation by the “spray as you go” (local anesthetic) technique. In the newer models, this internal working channel has been eliminated to make the scope easier to clean. The Bonfils was designed to be lightweight, durable, and portable. It comes in 2 other sizes with a 2-mm or 3.5-mm OD for use in children.
Preparation of the Device
The endotracheal tube (ETT) is loaded onto the scope body after silicon spray lubrication has been applied, and is locked at the proximal end by a detachable ETT holder. The distal beveled tip of the ETT should be aligned with the distal end of the Bonfils fiberscope. Continuous oxygen insufflation or suctioning within the loaded ETT, but outside the Bonfils shaft, is possible via the tube adapter. Oxygen insufflation serves to minimize fogging of the Bonfils' distal lens, and to disperse oral secretion away from the lens tip. Antifog solution applied to the lens improves visibility. It is important to ensure that the attached camera and video monitor system are focused and orientated correctly, because the attachment may be rotated.
For awake tracheal intubation, antisialagogue drugs and sedatives may be administered to the patient. The patient is positioned supine with the head in neutral position. For better ergonomics, the operating table is adjusted to the lowest position, or a standing stool may be used for the operator.
The manufacturer recommends the retromolar oral insertion technique, whereby a small mouth opening is sufficient and the patient's head does not need to be hyperextended. The left hand first performs a chin-lift by grasping the mandible and the tongue to expose the laryngeal inlet.
In the retromolar approach, the scope is inserted from the right side of the patient's mouth, alongside the molars, and advanced underneath the epiglottis. The distal end is rotated to view the epiglottis. The scope is then carefully guided through the glottic aperture, until tracheal rings can be identified. When the tip of the Bonfils is in satisfactory position, the ETT may be advanced (“railroaded”) into the trachea using gentle corkscrew motions after releasing it from the ETT holder.
Some authors caution against this technique of advancing the tip of the Bonfils through the glottic aperture, because the risk of tracheal injury may increase. However, inadvertent esophageal intubation or arytenoids injury may occur if the Bonfils tip is positioned outside the trachea at the laryngeal aperture before advancement of the ETT.11
Alternatively, the scope could be advanced midline until the epiglottis is reached. Maintaining a midline position is easier for the beginner to locate the glottis. Instead of a chin-lift or jaw thrust maneuver, direct laryngoscopy also increases the retropharyngeal space before the introduction of the Bonfils. When the tip of the ETT passes the vocal cords, the laryngoscope can be withdrawn and the ETT advanced into the trachea.12,13 Tips and troubleshooting techniques are summarized in Table 1.
Cleaning the Device
After each use, the Bonfils fiberscope is cleaned and sterilized. It should first be cleaned with a disinfectant (e.g., quaternary ammonium compounds) to remove visible soilage. The oxygen insufflation channel should be rinsed. The Bonfils is then immersed fully in the disinfectant, rinsed with water, and dried. As an alternative to the manual cleaning described, machine cleaning and disinfection are possible. Sterilization can then be performed using steam or chemicals, according to nationally applicable recommendations.
Evidence of Bonfils Use in the Literature
The use of the Bonfils has been described in normal airways, difficult airways, and for awake intubation. Overall successful intubation in “predicted normal airway” patients and “predicted difficult or difficult airway” patients was 96.4% (confidence interval 0.93–0.98, n = 247) and 95.6% (confidence interval 0.88–0.99, n = 69) in a quantitative review and meta-analysis.10 Clinical reports of the Bonfils are summarized in Table 2.
Use of the Bonfils in the Normal Airway
There are several case series describing the use of the Bonfils in normal airways. In the largest, 60 patients with normal airways undergoing elective otorhinolaryngology surgery were recruited.12 The operators learned the insertion technique by observing a colleague, but otherwise kept their exposure to the endoscope limited. After induction of anesthesia and muscle relaxation, the Bonfils was introduced via the midline or lateral approach after the chin-lift maneuver. Intubation success was 98.3% with median (interquartile range [range]) time to intubation of 33 seconds (24–50 [13–180] seconds). External jaw thrust was used in 3 cases and gave an advantage in 2. Maximal neck extension was used on one occasion and was effective.
In an earlier report by the same authors studying 16 patients with normal airways undergoing general anesthesia, the success rate of intubation was 100%.a Based on their preliminary experience with the Bonfils fiberscope, a learning curve of 20 patients was suggested, a recommendation supported by Corbanese and Morossi.14 The authors commented that the use of the Bonfils was not intuitive and a learning process was required. Even when a clear view of the laryngeal inlet was achieved, the curve on the instrument did not allow straightforward advancement. Rather, a rotation movement to one side off the incisors was what moved the instrument along in the direction of the line of view. Once this aspect was mastered, use of the instrument became straightforward. Similarly, FOB is not necessarily intuitive, and many authors have commented on the time required to both learn the instrument and maintain the skill. The preliminary results of the Bonfils, in comparison, were encouraging.15
Wong et al.16 disputed the ease of use of the Bonfils in their series of 36 unselected patients (31 patients were intubated by one author and 5 patients by another). Their overall successful intubation rate was 86% and median intubation time was 80 seconds (range, 34–282 seconds). The Bonfils failed to facilitate tracheal intubation in 5 patients. In 3 patients, failure was attributed to an inability to locate the laryngeal inlet. Equipment failure occurred during one case, and esophageal intubation in another, because of difficulty in disengaging the ETT from the holder. One of the failures was in a patient with limited mouth opening (<2 fingerbreaths). The authors found that jaw thrust by an assistant improved the view in 31% of patients; their 2 most common problems were disengagement of the tube from its slide-cone locking collar (28%), and fogging of the lens (11%).
Comparative Studies of the Bonfils with Other Airway Devices
Comparison with Flexible FOB
In a multicenter, prospective, randomized controlled trial, 116 patients with Cormack and Lehane grades III and IV and/or those requiring >2 laryngoscopy attempts were included to undergo Bonfils- or FOB-aided tracheal intubation.17 The endoscopic view was better, and the time to intubation shorter, in the Bonfils group. The median (range) time to intubation in the Bonfils group was 160 seconds (45–907 seconds), compared with the FOB group's 229 seconds (81–720 seconds). Complications were minor and similar in both groups. It was interesting to note that intubation failed in 3 patients in the FOB group. Of these 3 patients, intubation was eventually achieved with the Bonfils in 2 patients and with a Macintosh blade in 1 patient.
In the second study, 40 patients who had unanticipated difficult laryngoscopy were randomized to undergo intubation with either FOB or Bonfils, both assisted by direct laryngoscopy.b Intubation was achieved faster with the Bonfils than with the FOB, 77.9 ± 41.2 seconds versus 145.5 ± 83.9 seconds. Successful intubation was 100% in the FOB group. Intubation was not possible in 2 patients with the Bonfils, resulting in a success rate of 90%. There were no significant differences in the incidence of sore throat, hoarseness, and hemodynamic changes during tracheal intubation. This is not unexpected, because both patient groups underwent direct laryngoscopy. In the FOB group, an assistant was needed to perform the direct laryngoscopy, whereas in the Bonfils group, the main operator was able to perform direct laryngoscopy and manipulate the Bonfils. Also, intubation failure might not have been directly attributable to the instrument used. The success of direct laryngoscopy also affected the duration and success of intubation.
Both the FOB and the Bonfils offer high rates of intubation success. The FOB is the “gold standard” in difficult airways and for awake intubation, and is a component of the difficult airway algorithm.3 Advantages over the Bonfils include the ability to suction the airway and aid intubation via the nasal route. Most centers would more frequently have the FOB available than the Bonfils, allowing trainees to practice its use.
However, preparation of the Bonfils requires shorter time, and the ability to observe ETT advancement between the vocal cords minimizes the risk of injury. Fiberoptic intubation with a Bonfils endoscope has definite advantages. In some instances, FOB-aided tracheal intubation may be difficult or even impossible after the induction of anesthesia and muscle relaxation, because of collapsed pharyngeal tissues or large tongue. The Bonfils' rigid structure helps to displace such collapsed soft tissue and allows advancement past the obstruction. Large, floppy epiglottis or mobile, solid tumors may be physically lifted to gain access to the glottic opening.
Endoscopic orientation of the Bonfils is better than the FOB. In addition, only one hand is required for maneuvering and there is better translation of hand movements to scope movements. The Bonfils is also less expensive and faster to assemble than the FOB. Unlike the FOB, the Bonfils is sturdier, more portable, and may be useful in the emergency situation in which a trauma or collapsed patient requires rapid intubation.
Comparison with the Macintosh Laryngoscope
Byhahn et al.13 compared the Bonfils with the Macintosh blade for tracheal intubation in elective gynecological patients with simulated difficult airways. The mouth opening and neck movement were restricted with the use of rigid cervical collars. In these 76 patients, the authors found that successful intubation was achievable in only 39.5% using a Macintosh and in 81.6% using Bonfils (within 2 attempts). Time to successful intubation was not statistically different between the groups, (53 ± 22 seconds with the Macintosh blade, compared with 64 ± 24 seconds with the Bonfils). After removal of the collar, all patients in whom tracheal intubation failed had successful intubation with the Macintosh, without any complication.
The Bonfils was a more effective intubating device for patients with immobilized cervical spine and significantly limited interincisor distance. The main reason for the 18.4% failure rate in the Bonfils group was the inability to direct the rigid Bonfils underneath the epiglottis in these patients whose neck movements and mouth openings were restricted. In this study, the use of a bougie or other airway adjuncts in the Macintosh group was not mentioned and hence assumed not allowed. Perhaps the intubation success of the Macintosh would have been greatly improved if adjuncts were used as in everyday practice.
In a study conducted by Wahlen and Gercek,18 the time to intubation using either the Bonfils or the Macintosh blade was compared in patients with normal cervical spines. Intubation was achieved faster with the Macintosh blade (18.9 ± 7.1 seconds) than with the Bonfils (52.1 ± 22.0 seconds). All patients' tracheas were intubated successfully on the first attempt with the Macintosh, whereas the success rate of Bonfils was 91.7%. As compared with the Macintosh blade, the benefits of the Bonfils may be more obvious in patients with limited neck movements and mouth openings. Although intubation time was significantly longer when the Bonfils was used in normal patients, the increased apneic time may not be clinically significant in patients who are administered adequate oxygen. Wahlen and Gercek also demonstrated that faster intubation with the Macintosh was achieved at the expense of greater cervical spine movement: Macintosh (22.5 ± 9.9 degrees) versus Bonfils (5.5 ± 5.0 degrees), which may not be desirable in certain patient groups.
To achieve tracheal intubation with conventional laryngoscopy, trauma patients with potentially unstable cervical spines frequently have the front portion of the immobilization collar removed. Cervical immobilization is then achieved by performing manual inline stabilization. When the Bonfils is used in these patients, intubation can be achieved under direct vision without the need for cervical collar removal or cervical spine movement, despite limited mouth opening.
It remains speculative whether the Bonfils' design allows for a technique that requires less leveraging and pressure on the teeth, hence decreasing the risk of dental injury.
Comparison with Intubating Laryngeal Mask Airway
Bein et al.19 compared the Intubating Laryngeal Mask Airway, Fastrach™ (The Laryngeal Mask Company, Singapore), and Bonfils in 80 elective surgical patients with clinical features predictive of difficult airways. Time to first adequate ventilation with the Fastrach was added to the time for placement of the tracheal tube to give an overall time required for tracheal intubation and facilitate comparison. As expected, the use of the Fastrach resulted in shorter median time (range) to first adequate ventilation: 28 seconds (6–85 seconds) versus 40 seconds (23–77 seconds) with the Bonfils. However, the median time required for tracheal intubation was longer for the Fastrach compared with the Bonfils: 76 seconds (45–155 seconds) versus 40 seconds (23–77 seconds). The first-time tracheal intubation success rate was better with Bonfils (97.5%) than with the Fastrach (70%). Patients in the Bonfils group also had significantly fewer incidences of sore throat and hoarseness. Hemodynamic variables, oxygen saturations, and Bispectral Index values were stable and similar in the 2 groups.
In the study by Bein et al., the cumulative success rate of tracheal intubation with the Fastrach in this group of patients was similar to another large multicenter study.20 The shorter time to first successful ventilation in the Fastrach group is advantageous in patients with limited respiratory reserves. The Intubating Laryngeal Mask Airway has been adopted by the UK Difficult Airway Society as the device of choice when the initial tracheal intubation fails.c
However, the quicker time to tracheal intubation in the Bonfils group may have been more important in patients at risk for pulmonary aspiration. Limited mouth opening in some patients may also prevent successful Fastrach insertion. In addition, insertion of the laryngeal mask airway is a blind technique, which may cause trauma to the oropharyngeal structures, especially when a friable tumor may be present. In contrast, the Bonfils allows visualization of the airway during the entire process of tracheal intubation. In these instances, the Bonfils may be preferable. In theory, a mouth opening at least equal to the OD of the ETT is sufficient for successful intubation.
In most comparative studies, subjects are frequently elective surgical patients undergoing general anesthesia and muscle relaxation before intubation attempts. Patients with a known history of difficult intubation, difficult mask ventilation, or with anatomical anomalies are usually excluded. Hence, the results from such studies may not be generalized to patients requiring emergency intubation, or to certain subgroups of patients with difficult airways. The variable success rates among the different devices also reflect preexisting operator experience, training, and psychomotor skills. As with the mastery of any tools, operator affinity and preference are important and yet intangible factors.
Comparison with Shikani Optical Stylet and Levitan FPS Optical Stylet
A. Shikani first described the Shikani Optical Stylet (Clarus Medical, Minneapolis, MN) in 1999.21 It is an inexpensive, reusable intubating stylet that has a lens at its distal end and a fiberoptic cable inside the stainless steel shaft, connected to a camera and a video monitor. Similar to the classic stylet, it is malleable and can be inserted into the ETT before intubation. Similar to the Bonfils, the Shikani allows continuous visualization of the airway during intubation. The use of the Shikani is also similar to that of the Bonfils, and its insertion does not require laryngoscopy. The adult-size Shakani can accommodate various ETT sizes (5.5–9.0), and the pediatric version supports sizes 3.5 to 5.0 ETT. An “adjustable tube stop” with an oxygen port allows the ETT to be firmly connected to the stylet and delivers oxygen.22
Clinical studies of the Shikani showed a success rate of 100% in 2 studies involving 140 surgical patients.21,22 This included 5 intubations in awake patients. The Shikani was also useful in 12 difficult pediatric airways, achieving successful intubation in 11 of these children with congenital syndromes, airway trauma, or tumors.23,24
The Levitan FPS Optical Stylet (Clarus Medical) differs from the Shikani by its shorter length (30 cm) that allows an ETT to be fitted directly onto the device without the need for a tube stop. It is designed to be used with laryngoscopy, and provides additional fiberoptic visualization. It comes in 1 size and fits ETT sizes 5.5 to 9.0. One retrospective review of 301 intubations with the Levitan performed or supervised by 1 anesthesiologist had 99.7% success in tracheal intubation, including rapid-sequence scenarios.25 The mean (SD) time to intubation was 23 (24) seconds.
A randomized crossover study that compared intubation with Bonfils versus Levitan by 12 anesthesiologists, showed a better first-attempt success rate with the Bonfils (73% vs 57%).26 Complications such as sore throat (13% vs 31%) and voice change (12% vs 26%) were also significantly less with the Bonfils. The eventual success rate for each of the devices was similarly high, however, at 94%. Other variables such as median total times to intubation (Bonfils 36 seconds vs Levitan 44 seconds) and ease of intubation scores were similar for both devices. The Bonfils and the Levitan were equally effective intubation aids in patients with normal airways when used by anesthesiologists who were previously unfamiliar with their use. However, this study suggests that in novice users, familiarity and skill development are necessary for better first-attempt success rates.
The main difference between the Bonfils and the Shikani or Levitan is the malleable, stainless steel stylet of the latter. One can mold the stylet to suit each patient, particularly those with abnormal airways. The Shikani has been reported to facilitate intubation via the Intubating Laryngeal Mask Airway.27 The manufacturer suggests that the bright illumination may also function as a lightwand, although there are no clinical studies supporting the claim. The other advantage of the Shikani or Levitan is that the illumination port is via a standard connector. This ensures that most, if not all “green fitting” laryngoscope handles will be suitable for providing the required illumination through the eyepiece and gives the device greater portability.
Limitations of the Shikani include a limited depth of view, only being in focus at a distance of approximately 1 cm. Other limitations are similar to the Bonfils, such as poor visibility when secretions cover the lens. The ability to pass the stylet any distance beyond the vocal cords is restricted because of its angulated shape, which results in its impinging against the anterior tracheal wall.23
In a randomized crossover study investigating the performance of Macintosh, Bonfils, GlideScope® (Verathon Inc., Bothell, WA), and CTrach ™ (The Laryngeal Mask Company) in a simulator using normal and difficult airways, all devices had a first-attempt success rate of >90%.28 Training to use the devices was accomplished by oral instructions and demonstration of the intubation technique. In this group of 63 participants with variable duration of anesthesia training, most preferred the use of Macintosh or GlideScope for intubation. A larger proportion of users rated Bonfils and CTrach as moderate or difficult to use.
In another manikin study comparing Bonfils with Macintosh, 30 physicians only familiar with the Macintosh blade were given a standardized demonstration of the Bonfils before participation.29 Intubation success was greater with the Macintosh in the “normal airway” and the “decreased cervical range of motion with jaw trismus” scenarios (Macintosh 100% vs Bonfils 82%, and 84% vs 76%, respectively). In the “tongue edema scenario, ” intubation success with Macintosh was 67% versus Bonfils 83% with similar durations of intubation attempts. In the 2 difficult scenarios, the Bonfils was rated easier to use as compared with the Macintosh.
It would be expected that most anesthesiologists are more familiar with the Macintosh laryngoscope or the similarly designed GlideScope, as compared with the Bonfils or CTrach, which likely introduced bias in these studies. Additionally, manikin studies may not correlate with clinical performance when evaluating intubation devices. Some believe the use of rigid plastics, lack of collapsible soft tissues, absence of secretions, and sometimes incorrect epiglottis and laryngeal structures make them unlikely to be useful surrogates for difficult airways when evaluating ease of intubation.10
Bonfils Fiberscope as a Rescue Device After Failed Intubation Attempts with Macintosh
Bein et al.30 described the use of Bonfils intubation fiberscope as a rescue device after failed intubation. Twenty-five patients scheduled for elective coronary bypass grafting had unanticipated difficult intubation after the induction of anesthesia and muscle relaxation. All patients had Cormack and Lehane grades III and IV laryngeal views despite optimization of patient positioning and Macintosh blade size. After 2 failed intubation attempts by an experienced anesthesiologist, a Bonfils fiberscope was used as an airway adjunct. Intubation with the Bonfils was successful in 24 patients (success rate 96%). In 1 patient, oral secretions obscured the view of the glottis; this patient's trachea was successfully intubated nasally with the FOB. Mean intubation time (interquartile range [range]) using Bonfils was 47.5 seconds (30–80 [20–200] seconds). No adverse event was observed.
The Use of Bonfils Fiberscope in Prehospital Emergency Setting
The Bonfils fiberscope has a versatile design that allows it to be portable. By using a battery as the light source and an eyepiece for viewing (rather than a separate screen), Bonfils can be easily transported and used in various offsite areas during emergency situations.
Byhahn et al.31 described 6 patients in whom Bonfils was used for emergency intubation in the field. Two patients experienced multiple traumas and had a rigid immobilization collar, mandible fracture, and midface hematoma. The airway was secured on the first attempt in both patients in 35 and 45 seconds. The third patient was a cardiac arrest victim who required advanced cardiac life support. Two conventional intubation attempts failed because of difficult airway (Cormack and Lehane grade IV view; body mass index 40 kg/m2). Intubation was successful with Bonfils on the first attempt despite poor patient positioning. The Bonfils was electively used in 3 other patients successfully in the field: 2 cardiac arrest victims and 1 intoxicated patient with respiratory arrest.
The Use of Bonfils Fiberscope for Awake Intubation
There are 3 studies that described awake intubation with Bonfils. The first described 5 patients with variable combinations of indicators of difficult airway anatomy, including limited mouth opening, limited neck movement, unstable cervical spine, and poor Mallampati class airway.32 The patients received IV glycopyrrolate 0.2 to 0.4 mg, midazolam 1 to 2 mg, droperidol 2.5 mg, and incremental doses of fentanyl 50 to 200 μg or sufentanil 10 to 20 μg. The oropharynx was topically anesthetized with lidocaine using an atomizer, and patients were positioned supine with their head and neck in a neutral position.
After oxygen administration, patients were instructed to open their mouths and protrude their tongues. The Bonfils fiberscope, preloaded with an 8.0-mm ETT, was advanced via the retromolar approach. Additional lidocaine was sprayed on the vocal cords and trachea via the Bonfils tube adaptor, and the ETT was then advanced over the scope. Spontaneous ventilation was maintained throughout the procedure, which proceeded uneventfully. Although it was possible to insufflate oxygen through the adaptor connected to the shaft of the Bonfils, this was not deemed necessary, because all intubations were completed within 3 minutes.
In the second series of 33 patients with ear, nose, and throat cancer and with predicted difficult airway, tracheal intubation using the Bonfils was successful in 94% of patients.33 The majority of the patients (91%) also reported a good or very good perception of the intubation.
In the third report, patients with a known difficult airway because of limited mouth opening, limited head and neck movement, or micrognathia, underwent tracheal intubation with the help of a novel method of topical airway anesthesia.34 A 20-gauge, multiorifice epidural catheter was placed in the suction channel of the Bonfils fiberscope. The proximal end of the epidural catheter was affixed to a Luer-locked syringe prefilled with lidocaine. After the Bonfils fiberscope was advanced in the airway until the tip was in front of the glottis, the epidural catheter was advanced into the upper trachea. Three to 4 mL of lidocaine was sprayed into the trachea, and the ETT was inserted after topical anesthesia 3 to 5 minutes later.
This modified method of spray-as-you-go airway topicalization is advantageous because the epidural catheter can be inserted into the trachea with the tip of the Bonfils positioned above the glottis. Airway topicalization is completed using the epidural catheter with fiberoptic visualization. By placing the distal orifices of the catheter in front of the Bonfils fiberscope, a clear view can be maintained during lidocaine spray. Thus, stimuli to the airway may be minimized in an awake patient and the administration of local anesthetic is more precise. However, in this report, the exact number of awake intubations and associated complications were not reported.
The Use of Bonfils Fiberscope in Patients with Obstructing Airway Tumors
Leong and Wongd described a case series of 5 patients with obstructing airway tumors in which the Bonfils proved to be very useful. All patients had large tumors arising from the base of the tongue, hypopharynx, epiglottis, or larynx. The first patient's trachea was intubated using the Bonfils after sedation and topicalization of the airway. Because the tumor occupied the pharyngeal space and completely obscured the larynx, the tip of the rigid Bonfils fiberscope was negotiated distal to the tumor via the left retromolar space.
The other 4 patients' tracheas were intubated after induction of general anesthesia. The versatility of the scope allowed intubation via the left or right retromolar approach, or via the midline approach depending on the location of the tumors. The rigidity of the Bonfils fiberscope shaft allows for easy translation of hand movements to movements of the distal end of the scope. Thus, unlike the FOB, which has little structural rigidity, the rigid Bonfils allows for gentle displacement of mobile tumors obstructing the glottic opening.
The Bonfils fiberscope enables intubation with minimal trauma to tumors or adjacent structures and tissue because of its small shaft diameter as compared with laryngoscopes. Unlike conventional laryngoscopes or even videolaryngoscopes, the lack of a leading edge that must displace the tissue before viewing the larynx also minimizes tissue injury. The wide angle of view allows visual assessment of aberrant anatomy to determine the feasibility of intubation. The authors concede that the learning curve to master the Bonfils fiberscope is steep. However, once the technique is mastered, the high degree of maneuverability of Bonfils is appreciated.
The Use of Bonfils Fiberscope with Double-Lumen ETTs
DLTs may occasionally be used in patients with respiratory diseases undergoing thoracic surgery. A difficult intubation in this group of patients is more challenging because of their poor respiratory reserves. Intubation may be impeded by the preformed, bulky DLT, and the patient's teeth can damage the 2 cuffs, making repeated airway manipulation necessary. The use of the Bonfils fiberscope to aid DLT intubation has been described in 2 patients after failed direct laryngoscopy.35
Because the DLT is longer than the Bonfils, the authors of the report shortened both the tracheal and the bronchial connectors to a length of 38.5 cm. The DLT's bronchial lumen was then mounted over the scope. The Bonfils was first inserted from the right side of the mouth along the molars, and then advanced into the glottic aperture. The DLT was inserted into the trachea under direct visualization. Although not specified, the authors reported that the time to intubation was clinically acceptable, and no dental or cuff trauma occurred. Shortening of the proximal connectors did not prevent their connections to the ETT adapter and subsequently to the right-angle adapter attached to the breathing circuit. In such cases, however, the clinician must remember that the correct position of the tube must ultimately be verified with an FOB.
The Use of Bonfils Fiberscope During Percutaneous Tracheostomy
FOB is primarily used to guide percutaneous tracheostomy in the intensive care unit. However, Buehner et al.36 postulated that the Bonfils fiberscope could provide adequate visualization without risk of damage to the scope from needle puncture during the procedure. The authors evaluated the original Bonfils fiberscope and 2 modified versions (straight and curved shaft). Although difficulty was experienced while passing the scopes through the angled tracheostomy tubes, the Bonfils and its modifications provided adequate views for the safe conduct of percutaneous tracheostomy without device damage. The procedure was completed using the Bonfils fiberscope in 37 of the 40 patients. In 2 instances, excessive secretions precluded the use of the fiberscope. One patient experienced pulmonary hemorrhage, and the use of the scope was abandoned.
The Use of Bonfils Fiberscope in the Pediatric Population
The Brambrink Retromolar Intubation Endoscope (Karl Storz GmbH) has a fine, 22-cm optical rod with an OD of 2.0 mm, suitable for ETT sizes of 2.5 to 3.5 mm. Similar to the adult version, it has a distal 40-degree curvature. The Bonfils fiberscope comes in 2 other sizes: OD 3.5 mm, suitable for ETT sizes 4.5 to 5.5 mm, and OD of 5.0 mm, suited for ETT sizes of ≥6.0 mm.
Bein et al.37 evaluated the pediatric Bonfils fiberscope for elective endotracheal intubation during anesthesia in children with normal airways. Fifty-five children (aged 6 ± 4 years) had tracheal intubation by a single operator experienced with the adult Bonfils fiberscope device. The success rates of tracheal intubation after the first and third attempts were 72.7% and 89.1%, respectively. Time to intubation in children who did not receive atropine pretreatment (and those with atropine pretreatment) was median 58 (58) seconds, interquartile range 35 to 100 (30–95) seconds, and range 14 to 377 (18–260) seconds. Among the 6 children in whom intubation failed, 1 patient developed bronchospasm whereas the remainder had copious secretions obscuring the glottic view. These children's tracheas were intubated uneventfully with conventional laryngoscopy. The subjective grading of Bonfils' handling was only “fair,” likely because of the smaller diameter and more malleable pediatric Bonfils fiberscope, which was also more fragile and susceptible to damage as compared with the adult version.
It was somewhat unsurprising that airway secretions contributed to such a large extent to the failure group. The pediatric Bonfils fiberscope's small lens size greatly magnifies even small amounts of secretions. This is compounded by the smaller pharyngeal space of the pediatric airway, such that lens contact with pharyngeal mucosa is more likely. Although enlargement of the pharyngeal space with direct laryngoscopy before the introduction of the Bonfils fiberscope may be useful, the laryngoscope blade competes for space and may limit the maneuverability of the Bonfils.38
In a randomized controlled trial of 50 healthy children aged 2 to 14 years, the Bonfils fiberscope was compared with conventional laryngoscopy.39 The Bonfils group underwent conventional direct laryngoscopy followed by Bonfils-aided intubation. The conventional group underwent laryngoscopy with Bonfils first, followed by conventional laryngoscopy and intubation. Successful intubation after 2 attempts in the Bonfils group and conventional group was 92.3% and 100%, respectively. The 2 patients experiencing failures in the Bonfils group were easily intubated with direct laryngoscopy. Although the success rate was poorer with the Bonfils fiberscope, the visualization of the glottis was better.
The Use of Bonfils Fiberscope in Children with Difficult Airways
There are several case reports of the use of the pediatric Bonfils in children with difficult airways, summarized in Table 3.40–42 In the last 2 reports, both authors concluded that the concurrent use of direct laryngoscopy increased the retropharyngeal space. This avoided “red out” of the Bonfils scope and contamination of the lens by secretions. Although useful in children with small airways, this combination technique has a limited role in patients with small mouth opening. A modified technique that uses an appropriately sized introducer of a laryngeal mask airway, ProSeal ™ (The Laryngeal Mask Company), was proposed to elevate the tongue off the posterior pharyngeal wall like a spatula.43,44 The thinner profile of the introducer may provide an advantage as compared with the bulkier laryngoscope blade.
Advantages and Indications of the Bonfils Fiberscope
A summary of advantages and indications of the Bonfils is presented in Table 4.
Reported Complications with the Use of the Bonfils Fiberscope
Hemmerling and Bracco45 reported a case of sudden extensive subcutaneous facial, orbital, and neck emphysema using a Bonfils fiberscope in a healthy 75-year-old with normal airway planned for elective intubation. After induction of general anesthesia and muscle relaxation, the fiberscope was advanced toward the epiglottis with oxygen insufflation at 10 L/min via the oxygen port. After 20 seconds, the patient's entire face swelled to resemble a puffer fish. Bonfils fiberscope–aided intubation was immediately terminated and the patient's trachea was intubated with conventional laryngoscopy. The aim of high-flow oxygen insufflation is to maximize apneic oxygenation, although the manufacturer suggests an oxygen flow of no more than 3 L/min be used.46 The cause of the adverse event was attributed to microscopic laceration of the mucosa caused by the high oxygen flow.
Limitations of the Bonfils Retromolar Intubation Fiberscope
The use of the Bonfils fiberscope is not readily intuitive; hence, the learning curve for its use may be high at the beginning. Because of the cost of purchasing and maintaining airway equipment, as well as the wide array of intubation devices available on the market, the Bonfils fiberscope may not be available in all centers. The lack of availability compounds the training difficulty with this device. As opposed to the Bonfils fiberscope, most other videolaryngoscopes are easier to learn. Most videolaryngoscopes use disposable blades that allow faster turnover and minimize cross-contamination among patients.
The main limitation of its use is the inability to perform nasal intubation with this fiberscope. Although the authors have successfully directed the nasally inserted ETT into the trachea by using the orally inserted Bonfils, this has not been reported in the literature. This limitation is in contrast to the FOB, which allows nasal intubation. The rigidity of the scope may increase the risk of airway trauma in inexperienced hands and the nonmalleable shaft may limit the ability to angle the scope in cases where the larynx is extremely anterior. As a result, the ETT may be trapped against the patient's teeth, making railroading of the ETT off the scope difficult.
As with most instruments that rely on indirect views of the airway, blood, secretions, and fogging of the viewing lens can seriously limit the usefulness of the Bonfils fiberscope. This is a major concern in the pediatrics population. As compared with the Macintosh laryngoscope when used in normal airways, intubation with the Bonfils takes longer and the lack of discernible advantages in this patient group may not justify its cost and use in everyday clinical practice.37
The Bonfils Retromolar Intubation Fiberscope is an effective tool for difficult intubations once mastery is achieved. It is robust, portable, and reliable. Its versatility allows its use in difficult situations such as unstable cervical spines, airway tumors, and awake intubations. It is also useful in normal airways when patients are at risk of sore throats or dental injuries. Bonfils fiberscope should be part of the armamentarium of any anesthesiologist planning to master the management of difficult airway.
Name: Sze-Ying Thong, MBBS, MMed (Anaes).
Contribution: This author designed the study, analyzed the data, and wrote the manuscript.
Attestation: Sze-Ying Thong approved the final manuscript.
Name: Theodore Gar-Ling Wong, MD, FRCPC.
Contribution: This author provided the idea for the study and edited the manuscript.
Attestation: Theodore Gar-Ling Wong approved the final manuscript.
This manuscript was handled by: Sorin J. Brull, MD, FCARCSI (Hon).
a Halligan M, Weldon B, Charters P. A clinical appraisal of the Bonfils intubating fibrescope. Br J Anaesth 2002;89:671–2.
b Kim SH, Woo SJ, Kim JH. A comparison of Bonfils intubation fiberscopy and fiberoptic bronchoscopy in difficult airways assisted with direct laryngoscopy. Korean J Anesthesiol 2010;58:249–55.
c Difficult Airway Society Guidelines. Default strategy for intubation including failed direct laryngoscopy. Available at: http://www.das.uk.com/guidelines/downloads.html. Accessed June 7, 2012.
d Leong KW, Wong GLT. The use of the Bonfils retromolar intubation fibrescope in securing the airway in five patients with airway tumours. ASEAN J Anaesth 2011;12:91–7.
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