Steering Sheath for 2-Nostril Transnasal Office Laryngoscopy

Introduction

Inclusion of operating channels in flexible transnasal laryngoscopes has expanded the capacity to treat laryngeal disorders under local anesthesia in an office-based setting. ¹ A large proportion of laryngeal surgical procedures have consequently been moved from the operating room to a clinic setting under local anesthesia to diminish the cost, discomfort, time, and risk of general anesthesia. ² This flexible endoscopic approach to the larynx is most commonly done through a single nostril with instrumentation through a working channel in a fiberoptic endoscope.

Current limitations to this approach include:

These shortcomings may be addressed by use of a disposable transnasal hollow steerable sheath through which instruments are directed by concurrent imaging through a standard transnasal endoscope in the contralateral nostril. The absence of an integrated lighting and optical system distinguishes this hollow steerable sheath from a channeled flexible transnasal laryngoscope.

Steerable sheath technology has reached advanced levels in other fields as highlighted by magnetic navigation systems controlling robotic deflectable sheaths used to direct radiofrequency ablation delivered through an endovascular transeptal approach to treat atrial fibrillation. ³

Less complicated steerable sheaths used in urology have previously been “steered” by manipulating a bent wire within a flexible sheath or rotating a semirigid sheath with a bent tip. A recently developed deflecting ureteral access sheath with a steering handle is now available (awaiting FDA approval for use in the United States) that can actively manipulate the angle of the tip.

The 2-nostril endoscopic technique has been described using flexible endoscopic imaging of the laryngopharynx through 1 nostril to direct placement of nasogastric tubes, suction catheters, and other instrumentation such as dilating balloons through the other nostril. We studied the use of this 2-nostril technique in the course of performing simulated transnasal laryngeal surgery through a hollow sheath with lever-manipulated steering capacity.

Methods

Simulated procedures employing transnasal endoscopic high-definition distal chip–digitally recorded laryngoscopy were performed in an otolaryngology office setting using an airway-management-trainer mannequin at the University of Iowa Otolaryngology Clinic (February 1, 2017). Similar testing was then repeated on human cadavers with standard transnasal flexible fiberoptic video laryngoscopy by COOK Medical Inc at the Medical Academic Center (Carmel, Indiana, USA; March 2, 2017).

Consultation with the University of Iowa Institutional Review Board provided assurance that U.S. federal guidelines exempt cadaver studies from specific protocol review.

The steering sheath employed was the Flexor 180™ deflecting ureteral access sheath (COOK^® Medical Inc, Bloomington, Indiana, USA) and is intended for 1-time use (disposable). This lever-manipulated deflecting ureteral access sheath with an inner diameter of 2.97 mm, an outer diameter of 4.95 mm, and a length of 45 cm is designed to provide working access to body cavities with a focus on urologic procedures. Control of the angulation of the tip of this sheath is through tension placed on a deflecting filament extending from the end of the sheath to a proximal lever (thumb actuator) (Figure 1).

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Figure 1.

(A) Handle for steerable sheath. (B) Flexible transnasal distal chip laryngoscope adjacent steerable sheath with biopsy forceps in place (C1, 2, 3, 4); angulation of sheath tip produced with manipulation of the lever.

Passive recoil to the original position by releasing the lever permits return of the tip to a straightened configuration. Three-dimensional positioning of instrumentation within the sheath is coordinated by this lever action coupled with rotation of the sheath and advancing or retracting either the sheath or the instrumentation within the sheath. The narrow low-definition fiberoptic system that is available with the assembly (Flexor^® Vue™ Deflecting Endoscopic System; COOK Medical Inc) was not used in our study.

Instrumentation tested through the steering sheath included injection needles (23-gauge Interject™ clear injection needle catheters with an outer diameter of 1.8 mm and a length of 200 cm; Boston Scientific, Spencer, Indiana, USA), biopsy forceps (Endojaw™ Model No. FB-231D with a maximal insertion portion diameter of 1.9 mm and working length of 115 cm; Olympus Medical Systems Corp., Tokyo, Japan), laser fibers (200-μ Holmium laser fiber; Laser Peripherals LLC, Plymouth, Minnesota, USA), and balloon dilators (CRE™ pulmonary balloon dilatation catheter, 10-12 mm; Boston Scientific, Cork, Ireland).

Results

Initial work with a mannequin in the clinic setting (University of Iowa Otolaryngology Clinic) permitted simulation employing traditional distal-chip endoscopic equipment through 1 nostril and using the steering sheath through the other nostril (Figure 2).

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Figure 2.

Simulation setup employing mannequin with high-definition flexible laryngoscope in right nostril and steering sheath in left nostril with tip past the left palate.

Manipulation of the steering sheath required practice to become proficient due to the less responsive movement of the steering sheath tip with lever manipulation when compared with that experienced with most flexible transnasal laryngoscopes. Despite this limitation, it was still possible to accurately position the 200-μ laser fiber for simulated vaporization of a superficial vocal fold lesion (Figure 3 A1, A2). The large diameter of the steering sheath permitted rotation of the biopsy forceps within the deployed sheath to appropriately orient the tips in a manner compromised by limited ability to similarly rotate the biopsy forceps with our current channeled scope (Figure 3 B1, B2).

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Figure 3.

The steering sheath directed instrumentation appropriately in contact with the free edge of the vocal fold with a 200-μ laser fiber (A1, A2) and biopsy forceps (B1, B2).

Management of instrumentation through the steering sheath permitted maneuvering to direct access to portions of the laryngopharynx in a manner independent of movement of the flexible laryngoscope placed in the opposite nostril. This technique permitted simulated injections to the right vocal fold without sacrificing imaging of needle tip location as occurs when the working channel is fixed to the right side of a channeled scope (Figure 4 A1, A2). A larger caliber balloon dilator (CRE 10-12 balloon) was readily placed and positioned through the steering sheath in a manner not possible through the smaller working channel of the currently available flexible laryngoscopes (Figure 4 B1, B2).

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Figure 4.

The steering sheath directed injection to the lateral aspect of the right vocal fold (A1, A2) and a dilating balloon into the subglottis and posterior glottis (B1, B2).

Further evaluation of the steerable sheath was performed in a cadaver lab, confirming the capacity to deploy instrumentation in normal human anatomy. Passage of the deflecting scope through the nose to the nasopharynx blindly (as was done in the mannequin) was more difficult through the normal cadaveric noses. Adaptation by using the flexible laryngoscope (imaging scope placed in the nostril above the steerable sheath) permitted ready advancement of the steerable sheath through the nostril to the nasopharynx. Once the tip of the steerable sheath was positioned in the nasopharynx, the flexible laryngoscope was then moved to the opposite nostril to direct the remainder of the procedure.

Discussion

The 2-nostril technique has been used for many years to improve access in the course of performing transnasal endoscopic pituitary surgery.^4,5 A meta-analysis of 30 studies (4805 patients) comparing mono-nostril versus bi-nostril techniques identified lower rates of diabetes insipidus and anterior pituitary insufficiency as well as shorter hospital stays when 2 nostrils were used. ⁶ The 2-nostril technique was associated with a higher rate of epistaxis and demonstrated a trend toward a higher rate of anosmia but also a trend toward better outcomes for invasive microadenomas.

Use of 1 nostril to accommodate a flexible imaging laryngoscope and the second nostril to direct placement of nasogastric tubes, to enhance flexible suctioning of the laryngopharynx, and to position balloon dilators has been reported.^7,8 This dual-nostril approach has also been applied using a channeled laryngoscope as a steering sheath through 1 nostril as it was directed by imaging provided by a standard laryngoscope in the other nostril. ⁹ To our knowledge, use of a large-bore hollow steering sheath to direct laryngeal and pharyngeal instrumentation has not been previously reported.

The ureteral access sheath, as was used in this study of a 2-nostril approach to the larynx, successfully addressed some of the shortcomings identified with use of a single channeled laryngoscope. The larger hollow bore permits manipulation (rotation) of biopsy forceps in a way that is compromised by the smaller channel in the laryngoscopes we have employed. Larger caliber instruments such as balloon dilators that cannot be passed through these small channels are readily passed through the steering sheath tested.

The decreased cost not only of the disposable steerable sheath itself but also of its maintenance (sterilizing and storage) offers a major advantage in comparison with the expensive channeled scopes that are prone to breakage and expensive to repair. Perspective is offered through analysis of maintenance problems with channeled ureteroscopes in identifying breakage (on average) following 44 uses of new scopes, 11.1 uses of broken scopes repaired by the original manufacturers, and 6.9 uses following repair by outsourced vendors. ¹⁰

The inability to suction when instrumentation obstructs the port in a channeled laryngoscope may be addressed by using a channeled flexible laryngoscope concurrently with the steering sheath. The open noninstrumented channel could be used to suction or, alternately, administer medications such as oxygen or topical anesthetic.

Shortcomings to the laryngeal application of the deflecting ureteral access sheath tested are apparent. Although use of the single standard channeled laryngoscope may permit manipulation of the scope and deployment by a single operator, in our experience, we consistently use an assistant. Use of the 2-nostril technique employing a steerable access sheath and a second imaging flexible laryngoscope would require a minimum of 1 assistant and possibly 2 assistants if a third assistant was used to assist with instrumentation. The technique to suspend the imaging scope in a fixed but maneuverable position has been validated by use during thyroplasty and could be applied to the 2-nostril approach if assistants are unavailable. ¹¹

The most notable shortcoming to use of the ureteral access sheath is the awkward manipulation of the tip created within the constraints of a single pulley system using passive recoil to restore the tip to its neutral position. Modification should be readily affected to develop a 2-pulley system such as that used to manipulate flexible transnasal laryngoscopes with more precision. Additional adaptation to shorten the access sheath to render it more applicable to laryngeal procedures may be of value.

Our experience offers the impression that until steerable access sheaths tailored for laryngeal application are made available, the ureteral access sheath was sufficiently functional in the experimental setting to be applied clinically.

Conclusion

The currently available (for research purposes) but not yet FDA approved hollow flexible steering sheath for urologic purposes is adaptable for use in the larynx. Further development to improve its design tailored to laryngeal procedures is anticipated to improve safety and efficacy as many laryngeal procedures that were formerly done in the operating room are moved to the clinic setting.