Percentage of successful exposures of regions of interest.
X-ray films of a patient undergoing telescopy with a 70° rigid telescope (A) and a 90° rigid telescope (B).
Views of the subglottic region taken by the 70° telescope (A) and the 90° telescope (B).
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.
Views of the anterior commissure taken by the 70° telescope (A) and the 90° telescope (B).
Views of the laryngeal surface of the epiglottis taken by the 70° telescope (A) and the 90° telescope (B).
Shao J, Stern J, Wang Z, Hanson D, Jiang J. Clinical Evaluation of 70° and 90° Laryngeal Telescopes. Arch Otolaryngol Head Neck Surg. 2002;128(8):941-944. doi:10.1001/archotol.128.8.941
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.
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.
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.
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.
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.
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 χ2 test to determine differences between the success rates of the 70° and 90° telescopes; χ2 tests were performed for each of the 4 regions of interest.
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).
No complications arose from the evaluation with either of the telescopes. Two 70° telescopies were discontinued due to patients' hyperactive gag reflexes.
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.
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
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.
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: email@example.com).