Manual of Emergency Airway Management, 3rd Edition

13.Fiberoptic Stylets and Guides

Calvin A. Brown III

Michael F. Murphy

Introduction

Rigid and semirigid fiberoptic stylets are novel intubating devices that permit visualization of the glottis indirectly (in contrast to the direct line of sight of direct laryngoscopy) through an image transmitted to an eyepiece via a fiberoptic bundle. Unlike flexible fiberoptic devices, the fiberoptics in rigid and semirigid devices are enclosed in a preformed curved steel stylet designed to navigate around the tongue and hypopharynx to visualize laryngeal structures, often with minimal mouth opening or neck mobility. These devices eliminate the need to straighten the angles of the upper airway to provide the direct line of sight that is required for direct laryngoscopy, thus allowing the clinician to “see around the corner.” This carries significant advantages; anatomical features such as an anterior larynx, cervical spine immobility, and limited mouth opening become less of an issue. Rigid stylets have nonmalleable curved metal sheaths, the shape of which cannot be altered, whereas semirigid devices, although not flexible, can be manipulated slightly to fit the particular airway geometry of each patient.

Semirigid stylets include the Shikani optical stylet (SOS) and the Levitan/“First Pass Success” (FPS) scope (Clarus Medical, Minneapolis, MN). Rigid stylets include the Bonfils Retromolar Intubation Fiberscope (Karl Stortz Endoscopy, Tuttlingen, Germany) and the Airway RIFL (Rigid Intubating Fiberoptic Laryngoscope; AI Medical Devices, Inc., Williamstown, MI). New intubating stylets, all similar in shape and principle, are appearing on the market at regular intervals.

Although these devices are not yet a routine part of emergency airway management, they have shown significant potential as alternative devices for the difficult airway or as rescue devices for the failed airway. Their clear advantages over direct laryngoscopy suggest that they will come into increasing use, even for “routine” emergency airways. They also may serve an expanding role in airway training because most devices can be fitted with eyepiece adapters that transmit the image to a video monitor.

The prototypical intubating stylet is the SOS; therefore, more time is devoted to its description, proper use, advantages, and contraindications. The other devices are similar in their core design and application, and are therefore described in less detail, highlighting specific features and differences.

Semirigid Stylets

Shikani Optical Stylet

The SOS is a semirigid stylet containing fiberoptic bundles for light and vision transmission (Fig. 13-1). The stylet, rounded distally at about 70 to 80 degrees, ends proximally in a high-resolution, fixed-focus eyepiece. The adult stylet can accommodate endotracheal tubes (ETTs) of 5.5 mm internal diameter (ID) or larger. A pediatric version is available and accommodates tubes of 3.0 to 5.0 mm ID. A bright halogen light is supplied from an attachable power pack, which holds four AA batteries, but the stylet is also compatible with Green-specification fiber-optic laryngoscope handles or remote light sources via fiberoptic cable. A video camera can be applied proximally to the eyepiece for teaching purposes. A push-button power switch can be found on the top of the battery pack. An adjustable tube stop is mounted on the stylet to hold the ETT in the desired position. The tube stop incorporates an oxygen port, permitting insufflation of oxygen if indicated. The malleable distal section of the stylet can be adjusted by hand, increasing or decreasing the angle of the bend to conform to the patient's anatomy.

To prepare the SOS, an ETT is loaded on the stylet, with the distal end of the stylet positioned just proximal to the ETT tip, and stabilized in this position by adjusting the tube stop proximally. Prior to insertion, the stylet tip should be warmed with either warmed saline or a warm blanket. Antifog solution should be applied. The device is held by the fingertips and thumb of the dominant hand, with the battery pack cradled in the web space between the thumb and index finger and the pads of all other fingers resting on the anterior part of the eyepiece and proximal stylet (Fig. 13-2). Despite its appearance, the battery pack is not designed to be used as a handle. The ETT-stylet combination is then inserted into the mouth in the midline and advanced into the hypopharynx under direct vision. The entire stylet is oriented in the midline and advanced along its curve gently around the base of the tongue. A firm jaw lift/tongue pull during insertion will help maintain visual orientation through the scope. The operator should begin to visualize glottic structures through the eyepiece as the tip navigates the base of the tongue. The epiglottis should quickly come into view. Guide the stylet under the epiglottis to visualize the laryngeal inlet. A common error is to advance the fiberoptic tip too far into the hypopharynx as its inserted, giving a view of the posterior aspect of the hypopharynx, valleculae, or upper esophagus. To avoid this, ensure the primary motion of the scope is initially rotation around the tongue and not advancement into the hypopharynx. As with other intubating stylets, the instrument can be used in conjunction with direct laryngoscopy. For example, when an unanticipated grade III direct laryngoscopy (epiglottis only) occurs, the ETT-SOS stylet combination can be inserted under the epiglottis during direct laryngoscopy, and the glottic opening can then be sought through the eyepiece. With either technique, the ETT-stylet is advanced through the cords under visual guidance, and then the ETT is held in place as the stylet is pulled back with a large circular motion toward the patient's chest, facilitating removal (Fig. 13-3). Tube placement confirmation is with end-tidal carbon dioxide (CO₂), auscultation, and chest radiography, as for any other methods of intubation.

The SOS is advertised as being useful for the management of difficult and routine airways, with the video capability facilitating airway management teaching. In the teaching setting, coupling the device with a video system can greatly enhance success by eliminating any potential disorientation associated with the rocking motion of the scope.

The primary limitation of the SOS is its ability to maintain clear vision in the context of a tendency to fog and in the presence of secretions or blood. Fogging is largely eliminated by warming the lens and applying antifog solution, as described previously. Although secretions, vomitus, or blood can obscure the distal lens of the scope, two key design elements come into play:

1. The patient is typically supine, and, with the jaw thrust and tongue pull, most of the manipulation of the scope is occurring anterior to the location of the pooled liquids.

2. If the lens becomes obscured and cannot be cleared, it is quickly and easily removed, wiped, and reinserted in a matter of seconds.

Occasionally, the glottis cannot be visualized using the scope, and, in such cases, adjustment of the scope's curvature (usually increasing the angle, but sometimes decreasing it) provides an improved “line of sight.”

Levitan/FPS Scope

The Levitan/FPS scope is a small, semirigid fiberoptic stylet intended to be used in concert with a standard laryngoscope. Its preformed shape is similar to other intubating stylets but with a gentler curve (approximately 45 degrees); however, it can be modified to meet the unique geometry of each patient's airway (Fig. 13-4). It has a handle with a small battery pack that powers a light-emitting diode to provide illumination. A screw-down cap, rather than a push button, is used to activate the light source. The eyepiece is at the proximal end of the stylet, near the top of the battery pack. The mechanics of the Levitan/FPS are similar to the SOS with one important difference: the Levitan/FPS is intended to be used with a standard laryngoscope. An ETT should be cut to 26 cm because the stylet is shorter than the ETT, and then preloaded over the stylet. It is held in place by inserting the ETT connector into a round, nonadjustable tube stop at the top of the scope. As with all intubating fiberoptic stylets, the distal end of the stylet is positioned within 0.5 cm of the ETT tip because positioning more proximally in the ETT defeats the wide-angle view characteristics of the lens and results in severe “tunnel vision.”

Unlike the SOS, the oxygen port is on the distal part of the handle and not attached to the adjustable tube stop. A flow of 5 to 10 L/minute is intended to clear secretions and avoid hypoxia during laryngoscopy and tube placement. However, this practice has led to gastric insufflation and perforation during flexible fiberoptic–assisted intubation and should be used with caution.

The Levitan/FPS scope is intended to be of particular benefit in patients with Cormack-Lehane view grade 3 on direct laryngoscopy. If a poor view is obtained by direct laryngoscopy, the operator positions the Levitan/FPS scope with mounted ETT so the tip of the scope is under the proximal tip of the epiglottis. The operator then looks through the eyepiece to visualize the laryngeal inlet (Fig. 13-5). When vocal cords are seen, the entire apparatus is advanced into the trachea. The laryngoscope is then removed. The stylet is removed from the well-immobilized tube in a fashion similar to that described previously for the SOS. Tube confirmation is done in the standard fashion with immediate end-tidal CO₂ detection and auscultation, followed by chest radiography. In the event that laryngoscopy identifies a grade 4 view, the loss of the epiglottis as a landmark greatly impairs the effectiveness of the scope. In such cases, the scope might be used to search for the epiglottis, which, if found, might allow repositioning of the direct laryngoscope to achieve a grade 3 view.

Rigid Stylets

Bonfils Retromolar Intubating Fiberscope

The Bonfils fiberoptic stylet uses high-grade fiberoptic bundles for light and vision transmission in a manner analogous to that of the SOS (Fig. 13-6). Unlike the SOS, which is inserted in the midline of the mouth, the Bonfils is intended to use a paraglossal or retromolar approach, capitalizing on the proximity of the glottis to the third (most posterior) molar. The rationale for this approach is discussed in Chapter 6. The stylet incorporates a distal bend to approximately 45 degrees and ends proximally in an eyepiece, which unlike the SOS is moveable, permitting easier use. This confers a substantial technical advantage for the Bonfils over the SOS. A small tube holder device on the shaft of the stylet enables the loaded ETT to be mounted at a position of the clinician's choice. The continuous insufflation of oxygen reduces fogging during use, but an antifog solution is advised. The earlier caveat applies regarding the risk of gastric insufflation and perforation by oxygen insufflation. The Bonfils is intended to be used by itself, but it can also be used in conjunction with direct laryngoscopy.

A small combination battery pack and light source affixes near the proximal end of the stylet, making the device light and easily manipulated. A conventional external fiberoptic light source cable can be used in place of the self-contained pack, if desired. A standard video adapter can be attached to the eyepiece, as for the SOS, and is particularly helpful for learning how to use the Bonfils.

The Bonfils has been used extensively in Europe and in a few North American sites for both routine intubations and difficult airways, but, as with the SOS and Levitan/FPS, there is insufficient literature to draw conclusions about its performance in large series, and there are no published head-to-head comparisons with other devices.

Airway RIFL

The Airway RIFL is a hybrid intubating device with a rigid stylet that ends in a flexible tip that can be dynamically and continuously adjusted by a proximal trigger up to a 135-degree angle (Fig. 13-7). Similar to other devices, a fiberoptic bundle transmits an image to the eyepiece. The manufacturer's literature states that it is intended for use in difficult airways and awake intubations, and can be used both with and without direct laryngoscopy. It uses a bright LED light source and can accommodate ETT size 6.5 and higher. There is no pediatric model. The RIFL is cleaned with STERIS or Cidex OPA. At the time of this writing, the RIFL is approved and commercially available. It is currently being field-tested and is under trial with the U.S. Army, but to date no literature or significant real-life experience exists.

Summary

Intubating fiberoptic stylets and video-assisted laryngoscopy (see Chapter 14) represent the vanguard of emergency airway management. The clear design advantages offered by these thin, curved, and often malleable introducers have the potential to make both routine and difficult intubations more successful and safer for patients. The primary advantage is the elimination of the need to create a straight line of sight from outside the patient's mouth to the glottic aperture, the major barrier to successful direct laryngoscopy. By positioning the “viewing port” at the distal end of a stylet, these fiberoptic intubating stylets offer a terrific advantage over direct laryngoscopy, allowing the operator to “steer” the distal end of the ETT through the cords. Considerable work needs to be done to fully evaluate these devices in the emergency arena; however, it seems reasonable that some, if not all, of the benefit seen in anesthesia literature would apply to patients requiring emergency airway management.

Evidence

1. Do we have any proof that the SOS is superior to direct laryngoscopy? There are no emergency-based studies evaluating the performance of optical stylets in emergency airway management. Existing studies are relatively small reports in the anesthesia literature using healthy elective surgical patients. Shikani (1) first described its use in the management of difficult airways in adults and children undergoing elective otolaryngologic surgery. Agro et al. (2) did a performance assessment with the SOS in 20 healthy preoperative surgical patients and successfully intubated 14 out of 20 patients on the first attempt. The remaining 6 were successfully intubated on subsequent attempts. They also observed negligible affects on hemodynamics, a property that could be beneficial in emergency patients with head injury. Only one case report describes its use in emergency airway management, where it was successfully used to intubate an obese patient with chronic obstructive pulmonary disease (3). Many versions of fiberoptic stylets exist; the literature to date suggests they are useful adjuncts and perform superiorly to direct laryngoscopy in both real and simulated difficult airway scenarios (4,5). Their use has been described in pediatric difficult airways as well (6,7). Their role in trauma patients, although not described in the literature, may also expand because intubating stylets appear to cause less C-spine motion than direct laryngoscopy (8).

2. Are there any studies supporting the use of the Levitan/FPS stylet? Similar to other fiberoptic devices, there is little literature describing use of the Levitan/FPS scope in emergency airway management, although it has been suggested that it can and should be used in both difficult and routine intubations (9). More data are required before a firm recommendation can be made. Overall, the role of fiberoptic intubating stylets in emergency airway management has yet to be defined.

3. What is known about the Bonfils Retromolar Intubating Fiberscope? Several small studies have been published in the past few years on the Bonfils fiberscope and its performance in elective surgical patients. One recent European case series reported on six prehospital intubations, the majority being difficult intubations, with all six patients successfully intubated on the first attempt (10). The Bonfils appears to be highly successful in routine airways as well. Haligan and Charters (11) published a report of 60 healthy preoperative patients and found an intubation success rate of more than 98%. A study of its use in predicted difficult airways identified equivalent success to the intubating laryngeal mask airway (LMA), with the Bonfils-assisted intubations being significantly more rapidly achieved than those using the LMA (12). Overall intubation times range from 30 to 60 seconds across several studies. Like other intubating stylets, the Bonfils may find an expanding role in trauma airway management because similar findings of reduced cervical spine motion during intubation have been reported (13). It also appears to be a successful rescue device following multiple failed direct laryngoscopic attempts by anesthetists (14).

4. Are there any published studies involving the Airway RIFL? At the time of this writing, there are no studies of the Airway RIFL.

References

1. Shikani AH. New “seeing” stylet-scope and method for the management of the difficult airway. Otolaryngol Head Neck Surg 1999;120:113–116.

2. Agro F, Cataldo R, Carassiti M, et al. The seeing stylet: a new device for tracheal intubation. Resuscitation 2000;44:177–180.

3. Kovacs G, Law AJ, Petrie D.Awake fiberoptic intubation using an optical stylet in an anticipated difficult airway. Ann Emerg Med 2007;49(1):81–83.

4. Liem EB, Bjoraker DG, Gravenstein D. New options for airway management: intubating fibreoptic stylets. Br J Anaesth 2003;91:408–411.

5. Biro P, Weiss M, Gerber A, et al. Comparison of a new video-optical intubation stylet versus the conventional malleable stylet in simulated difficult tracheal intubation. Anaesthesia 2000;55:886–889.

6. Pfitzner L, Cooper MG, Ho D. The Shikani seeing stylet for difficult intubation in children: initial experience. Anaesth Intensive Care 2002;30:462–466.

7. Shukry M, Hanson RD, Koveleskie JR. Management of the difficult pediatric airway with Shikani optical stylet. Paediatr Anaesth 2005;15(4):342–345.

8. Turkstra TP, Pelz DM, Shaikh AA, et al. Cervical spine motion: a fluoroscopic comparison of Shikani optical stylet vs. Macintosh laryngoscope. Can J Anaesth 2007;54(6):441–447.

9. Levitan RM. Design rationale and intended use of a short optical stylet for routine fiberoptic augmentation of emergency laryngoscopy. Am J Emerg Med 2006;24(4):490–495.

10. Byhahn C, Meininger D, Walcher F, et al. Prehospital emergency endotracheal intubation using the Bonfils intubation fiberscope. Eur J Emerg Med 2007;14(1):43–46.

11. Halligan M, Charters P. A clinical evaluation of the Bonfils intubation fibrescope. Anaesthesia 2003;58(11):1087–1091.

12. Bein B, Worthmann F, Scholz J, et al. A comparison of the intubating LMA and the Bonfils intubating fiberscope in patients with predicted difficult airways. Anaesthesia 2004; 59(7):668–674.

13. Wahlen BM, Gereck E. Three-dimensional cervical spine movement during intubation using the MacIntosh and Bullard laryngoscopes, the Bonfils fibrescope and the intubating LMA. Eur J Anaesthesiol 2004;21(11):907–913.

14. Bein B, Yan M, Tonner PH, et al. Tracheal intubation using the Bonfils intubation fiberscope after failed direct laryngoscopy. Anaesthesia 2004;59(12):1207–1209.