The Laryngoscope Lippincott Williams & Wilkins, Inc. © 2005 The American Laryngological, Rhinological and Otological Society, Inc. A Quantitative Study of the Medial Surface Dynamics of an In Vivo Canine Vocal Fold during Phonation Michael Doellinger, PhD; David A. Berry, PhD; Gerald S. Berke, MD Objectives/Hypothesis: The purpose of this study was to measure the medial surface dynamics of a ca- nine vocal fold during phonation. In particular, dis- placements, velocities, accelerations, and relative phase velocities of vocal fold fleshpoints were re- ported across the entire medial surface. Although the medial surface dynamics have a profound influence on voice production, such data are rare because of the inaccessibility of the vocal folds. Study Design: Medial surface dynamics were investigated during both nor- mal and fry-like phonation as a function of innerva- tion to the recurrent laryngeal nerve for conditions of constant glottal airflow. Methods: An in vivo canine model was used. The larynx was dissected similar to methods described in previous excised hemilarynx experiments. Phonation was induced with artificial airflow and innervation to the recurrent laryngeal nerve. The recordings were obtained using a high- speed digital imaging system. Three dimensional co- ordinates were computed for fleshpoints along the entire medial surface. The trajectories of the flesh- points were preprocessed using the method of Empir- ical Eigenfunctions. Results: Although considerable variability existed within the data, in general, the medial-lateral displacements and vertical displace- ments of the vocal fold fleshpoints were large com- pared with anterior-posterior displacements. For both normal and fry-like phonation, the largest dis- placements and velocities were concentrated in the upper medial portion. During normal phonation, the mucosal wave propagated primarily in a vertical di- rection. Above a certain threshold of subglottal pres- sure (or stimulation to the recurrent laryngeal nerve), an abrupt transition from chest-like to fry-like pho- nation was observed. Conclusions: The study reports unique, quantitative data regarding the medial sur- face dynamics of an in vivo canine vocal fold during phonation, capturing both chest-like and fry-like vi- bration patterns. These data quantify a complex set of dynamics. The mathematical modeling of such com- plexity is still in its infancy and requires quantitative data of this nature for development, validation, and testing. Key Words: Vocal fold vibration, quantitative measurements, medial surface, hemilarynx, high- speed imaging. Laryngoscope, 115:1646–1654, 2005 INTRODUCTION Quantitative measurement of the medial surface dy- namics of the vocal folds is important for understanding how sound is generated within the larynx. However, such data are difficult to obtain because of the inaccessibility of the vocal folds. Because of the small size and inaccessibil- ity of the larynx, the possibilities for imaging vocal fold oscillations are limited. Traditionally, in vivo high-speed recordings have been performed using endoscopic tech- niques that yield only a superior view of the vocal folds. Because of this orientation, the medial surface of the vocal folds cannot be seen during glottal closure. Indeed, many aspects of mucosal wave propagation are obscured during the glottal cycle, including the phase delay between the lower and upper part of the vocal folds, which is critical for maintaining normal phonation and which may be used to estimate the viscoelastic properties of vocal fold tissues. 1 Using an in vivo hemilarynx methodology presented earlier, 2 the present study reported the medial surface dynamics of an in vivo canine vocal fold during phonation as a function of innervation to the recurrent laryngeal nerve (RLN), for conditions of constant glottal flow. In particular, displacements, velocities, accelerations, and relative phase velocities of vocal fold fleshpoints were reported across the entire medial surface of the vocal fold. Minimum glottal area was also analyzed. Where possible, results were discussed and compared with previous obser- vations and hypotheses regarding vocal fold vibration. MATERIALS AND METHODS Experimental Set-Up A male mongrel canine (25 kg) was selected for the study. The animal experiment described in this manuscript was permit- From The Laryngeal Dynamics Laboratory, Division of Head and Neck Surgery, UCLA School of Medicine, Los Angeles, California, U.S.A. Editor’s Note: This Manuscript was accepted for publication June 8, 2005. Supported by Grant DC003072 from NIH/NIDCD. Send Correspondence to Michael Doellinger, The Laryngeal Dynam- ics Laboratory, Division of Head and Neck Surgery, UCLA School of Med- icine, 31-24 Rehab Center, 1000 Veteran Avenue, Los Angeles, CA 90095- 1794. E-mail: michael.doellinger@gmx.net DOI: 10.1097/01.mlg.0000175068.25914.61 Laryngoscope 115: September 2005 Doellinger et al.: Vocal Fold Dynamics 1646