Use of the rabbit larynx in an excised larynx setup

Abstract

Objective: To modify the excised larynx bench apparatus to accommodate experiments with rabbit larynges.

Study design: Methodological study using ex vivo rabbit larynges.

Methods: Rabbit larynges (n=5) were dissected and mounted on a custom-made phonatory apparatus. The arytenoids were adducted by rods, and humidified air was passed through the larynx to elicit vocal fold vibration. Acoustic, aerodynamic, electroglottographic (EGG), and videokymographic data were collected for each larynx. The same data were collected for five canine larynges for the purpose of comparison, and coefficients of variation were calculated for each parameter in both models.

Results: Reliable phonation was achieved in each larynx. Acoustic fundamental frequency (F(0)), percent jitter, percent shimmer, signal-to-noise ratio, pressure and flow at phonation onset and offset; and F(0), closed quotient, speed quotient, jitter, shimmer, and contact quotient, as recorded by EGG; and mucosal wave amplitude and phase difference are reported for rabbit larynges. Coefficients of variation for each parameter are similar in magnitude between the two models.

Conclusion: We developed a method for recording reliable acoustic, aerodynamic, videokymographic, and EGG data from rabbit larynges. When data obtained from leporine larynges were compared with data from canine larynges, the intralarynx variability of rabbit larynges was found to be similar to that of canine larynges.

Figure 1

A schematic showing the vocal fold tissue layers in rabbit, human, and canine larynges.

Figure 2

A: A rabbit larynx dissected to expose the vocal folds. All excess tissue has been cut away, and the epiglottis and excess thyroid cartilage have been removed. B: The rabbit larynx is mounted on a custom apparatus using a Luerlock, a zip-tie, and Loctite glue. The arytenoid cartilages are adducted by rods to produce phonation, and adequate anterior-posterior elongation is achieved through the placement of a suture in the thyroid cartilage at the level of the vocal folds. EGG electrodes are attached on either side of the thyroid cartilage at the level of the vocal folds by electrical tape.

Figure 3

A diagram of the excised rabbit larynx mounting system. A shows a rear angle view of the setup. B shows a frontal view with both adduction apparatuses and the elongation apparatus viewable. A= Smooth rod used for manipulation of the arytenoid cartilages, which allows for control of vocal fold adduction levels; the angle was found to be necessary to obtain approximation on the inferior margin of the vocal fold B= Spring-loaded mounting rods that allow for AP positioning of the threaded rod (A) C= The base of the system. It has channels to allow for AP movement of the rods used for arytenoid adduction and D= Symmetric AP elongation apparatus. Suture is tied to the thyroid cartilage at the anterior commissure and connected to this apparatus which can be positioned in the same manner as (B) E= Plastic mount for the larynx. A portion of the trachea is left and clamped to this mount. This provides stability for the larynx and an entry point for airflow. F= The tube connector used as an interface between the building source of pressurized air and the phonation system G= Extra pieces of metal rod used to clamp the phonation system to a laboratory bench. This will be removed once the system is incorporated into a laboratory bench.