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Clinical Evaluation of 70° and 90° Laryngeal Telescopes
Jun Shao, MD;
Jennifer Stern, BS;
Zheng-Min Wang, MD;
David Hanson, MD;
Jack Jiang, MD, PhD
Arch Otolaryngol Head Neck Surg. 2002;128:941-944.
ABSTRACT
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Objectives Rigid telescopy is widely used in otorhinolaryngology for endolaryngeal
visualization. Laryngeal telescopes are made with several angles, including
70° and 90°. In this study, the performances of 70° and 90°
telescopes are compared and evaluated on the basis of ability to visualize
specific regions of the larynx.
Methods Each subject (N = 121) received evaluation with both 70° and 90°
telescopes. The investigator used the telescopes to attempt to visualize 4
key regions: (1) the subglottic area, (2) the pyriform fossae, (3) the anterior
commissure, and (4) the laryngeal surface of the epiglottis. The telescopes
were connected to a video camera and videotape recordings were made. The percentage
of attempted visualizations that were successful was calculated for both the
70° and the 90° telescopes.
Results The 70° telescope provided successful visualization of the subglottic
area in 111 patients (91.7%), of the pyriform fossae in 115 (95.0%), of the
anterior commissure in 112 (92.6%), and of the laryngeal surface of the epiglottis
in 114 (94.2%). The 90° telescope provided successful visualization of
the subglottic area in 103 patients (85.1%), of the pyriform fossae in 112
(92.6%), of the anterior commissure in 100 (82.6%), and of the laryngeal surface
of the epiglottis in 102 (84.3%). Differences in rates of visualization were
significant for the posterior surface of the epiglottis, the anterior commissure,
and the subglottic area.
Conclusions The 70° telescope provided a significantly higher rate of successful
visualization for 3 of the 4 regions studied. This result contributes information
that may help the clinical examiner select an instrument of choice.
INTRODUCTION
FIBEROPTIC TECHNOLOGY, introduced in the 1970s, has an increasingly
important role in diagnostic medicine. Rigid telescopy, one fiberoptic application,
is widely used in otorhinolaryngology and has several advantages over the
alternative, traditional techniques of indirect mirror laryngoscopy and direct
laryngoscopy. The telescopic image is larger, brighter, and clearer, allowing
earlier diagnosis1 and aiding preoperative
and postoperative evaluation as well as physician-patient communication.2
The telescope has been widely applied as an adjunct to endoscopic surgery
of the larynx,3-4 and has been
reported to convey several advantages.5 Lore6 maintained that endolaryngeal visualization provided
by the telescope was excellent in the surgical context. Benjamin7
reported that for use in laryngeal photography, the telescope performed better
than either the fiberscope or the traditional laryngeal mirror. The telescope
has been recommended for use in routine screening8
as well as the endoscopy of neonates.9 Furthermore,
it has also been reported to improve imaging in pediatric endoscopy.10
Rigid telescopy confers advantages over the flexible fiberscope, an
alternative tool for use in laryngeal examination. While the association between
fiberscopy and laryngospasm is well known, to our knowledge, no such association
has been documented for the rigid telescope. As previously stated, telescopy
has been reported to achieve better performance than flexible fiberscopy for
use in laryngeal photography.7 However, like
the rigid telescope, the flexible fiberscope has been used in young children,11 and the flexible fiberscope may be better tolerated
in patients with limited cervical mobility and jaw movement.
Laryngeal telescopes are made with various angles; of these, the 70°
and 90° telescopes are 2 common varieties. The different angles allow
different physical approaches to the vocal tract. As a result, each telescope
angle is expected to allow preferential visualization of specific regions
without compromising patient comfort and tolerance. In this study, the abilities
of the 70° and 90° telescopes to visualize 4 key regions of the vocal
tract were evaluated and compared. Visualization of the subglottic area, the
pyriform fossae, the anterior commissure, and the laryngeal surface of the
epiglottis were attempted on subjects receiving both 70° and 90° telescopy.
These sites were chosen because they are frequently explored on clinical telescopic
examination, and because traditional indirect laryngoscopy often presents
difficulty in visualization of these regions. Visualization was considered
"successful" when the full region of interest could be visualized in an examination
that was tolerable to subjects.
PATIENTS AND METHODS
Outpatients reporting hoarseness and/or pharyngeal discomfort (N = 121)
served as subjects. The institutional review board of Northwestern University,
Chicago, Ill, approved this project, and patients gave informed consent. These
subjects were examined consecutively. Prescreening determination of patient
favorability to oral vs transnasal examination was not undertaken, thus adding
to the randomness of the patient sample. Of the 121 subjects, 61 were men
and 60 were women. The mean age of subjects was 43.7 years. Subjects were
evaluated by an otolaryngologist using both the 70° and 90° telescopes.
The examiner was a general otolaryngologist (J. Shao) with 7 years of experience.
Evaluations with both telescopes were performed in the same sitting, and the
sequence of telescopes used was random. Anesthesia (1% tetracaine hydrochloride
[Dicaine]) was offered to patients with active gag reflexes, which encompassed
approximately 11% of subjects.
The tip of the rigid telescope (models 8702P and 8706CJ; Karl Storz,
Culver City, Calif) was immersed in hot water to prevent fogging of the lens.
With one hand holding the tongue of the subject, the examiner inserted the
telescope through the oral cavity. A color video camera (model WV-KS152; Panasonic,
Osaka, Japan), and color monitor (model SV-950; Toshiba, Tokyo, Japan) were
used for visual feedback. Using the image on the monitor, the examiner guided
the telescope to view the laryngeal surface of the epiglottis, the anterior
commissure, the subglottic area, and the pyriform fossae.
The images obtained on the color monitor were video recorded. Videotapes
were reviewed for their inclusion of 1 or more of the 4 regions of interest:
(1) the laryngeal surface of the epiglottis, (2) the anterior commissure,
(3) the subglottic area, and (4) the pyriform fossae. Single frames that included
1 of these 4 areas were retained. Exposure of the 4 areas was attempted on
each patient; the percentage of visualizations that were successful, out of
a possible 121, were calculated for each of the 4 regions.
Statistical analysis included the use of the  2 test
to determine differences between the success rates of the 70° and 90°
telescopes; 2 tests were performed for each of the 4 regions
of interest.
RESULTS
Of the 121 subjects enrolled in this study, the 70° telescope provided
successful visualization of the subglottic area in 111 (91.7%). The 70°
telescope provided visualization of the pyriform fossae in 115 patients (95.0%),
of the anterior commissure in 112 patients (92.6%), and of the laryngeal surface
of the epiglottis in 114 patients (94.2%). The 90° telescope provided
successful visualization of the subglottic area in 103 patients (85.1%), of
the pyriform fossae in 112 patients (92.6%), of the anterior commissure in
100 patients (82.6%), and of the laryngeal surface of the epiglottis in 102
patients (84.3%). In all 4 regions of interest, the 70° telescope provided
a greater number of successful visualizations. The greater visualization by
the 70° telescope was statistically significant for the anterior commissure
(P = .03), the laryngeal surface of the epiglottis
(P = .02), and the subglottic area (P<.001). Differences between the 2 endoscopes were not significant
for the pyriform fossae (P = .59) (Figure 1).
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Figure 1. Percentage of successful exposures
of regions of interest.
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No complications arose from the evaluation with either of the telescopes.
Two 70° telescopies were discontinued due to patients' hyperactive gag
reflexes.
COMMENT
The x-ray films in Figure 2
illustrate the positioning of the 70° and 90° telescopes within the
vocal tract. Of the 2 endoscopes, the 70° telescope is able to approach
the vocal fold more closely. This closer physical approach may explain the
better visualization of the laryngeal surface of the epiglottis, the anterior
commissure, and the subglottic area by the 70° telescope.
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Figure 2. X-ray films of a patient undergoing
telescopy with a 70° rigid telescope (A) and a 90° rigid telescope
(B).
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Figure 3, Figure 4, Figure 5, and Figure 6 are derived from single video recording
frames using the 70°and 90° telescopes and show, respectively, the
subglottic area, the pyriform fossae, the anterior commissure, and the laryngeal
surface of the epiglottis. The frames obtained have sufficient lighting and
excellent clarity, as is consistent with the findings of others.6, 12
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Figure 3. Views of the subglottic region
taken by the 70° telescope (A) and the 90° telescope (B).
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Figure 4. Views of the pyriform fossae.
A, The left pyriform fossa, taken by the 70° telescope. B, The right pyriform
fossa, taken by the 90° telescope.
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Figure 5. Views of the anterior commissure
taken by the 70° telescope (A) and the 90° telescope (B).
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Figure 6. Views of the laryngeal surface
of the epiglottis taken by the 70° telescope (A) and the 90° telescope
(B).
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Our definition of a "successful visualization" took into account both
the ability to obtain a recording of the full region of interest and the tolerance
of patients to the procedure. If patient discomfort was too great, the telescopy
would be immediately discontinued at the patient's request and the examination
considered unsuccessful. In the course of this study, 2 patients requested
discontinuation due to hyperactive gag reflexes. To facilitate patient tolerance, patients were given anesthesia on request. A common preparation of topical
anesthesia for the pharynx and larynx involves 4% lidocaine or 2% tetracaine.2, 13 However, we were able to perform endoscopy
using 1% Dicaine. At this level of anesthesia, we encountered no serious complications
and patients were satisfied.
Of the 2 telescopes, the 70° telescope provided a higher rate of
successful visualizations of each of the 4 regions of interest; of these,
rate differences were significant for 3 regions. We believe that this finding
may be explained by the closer approach allowed by the 70° telescope.
In conclusion, the 70° telescope successfully visualized the anterior
commissure, the subglottic area, and the laryngeal surface of the epiglottis
in a greater percentage of patients. This result may be of potential use to
the clinical examiner selecting an instrument of choice.
AUTHOR INFORMATION
Accepted for publication February 13, 2002.
This study was supported in part by grant 1-R01DC05522-01 from the National
Institutes of Health.
This work was presented at the AAO-HNSF/ARO Research Forum, Denver,
Colo, September 9-12, 2001.
Corresponding author: Jack Jiang, MD, PhD, University of Wisconsin
Medical School, Department of Surgery, Division of Otolaryngology–Head
and Neck Surgery, 1300 University Ave, 5745 Medical Science Center, Madison,
WI 53706 (e-mail: jiang{at}surgery.wisc.edu).
From the Department of Otolaryngology, Shanghai Medical University,
Shanghai, China (Drs Shao and Wang); the Department of Otolaryngology–Head
and Neck Surgery, Northwestern University Medical School, Chicago, Ill (Ms
Stern and Dr Hanson); and Division of Otolaryngology–Head and Neck Surgery,
University of Wisconsin Medical School, Madison (Dr Jiang).
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