Toward Development of a Vocal Fold Contact Pressure Probe: Bench-Top Validation of a Dual-Sensor Probe Using Excised Human Larynx Models

Abstract

Featured Application: The goal of the current work is to validate a method for simultaneous measurement of vocal fold collision and subglottal pressures that can be used in vivo to better understand how collision contributes to voice disorders associated with vocal fold tissue trauma (like nodules and polyps) and to ultimately develop measures that will improve the prevention, diagnosis, and treatment of these disorders (e.g., a vocal fold collision dose).Abstract: A critical element in understanding voice production mechanisms is the characterization of vocal fold collision, which is widely considered a primary etiological factor in the development of common phonotraumatic lesions such as nodules and polyps. This paper describes the development of a transoral, dual-sensor intraglottal/subglottal pressure probe for the simultaneous measurement of vocal fold collision and subglottal pressures during phonation using two miniature sensors positioned 7.6 mm apart at the distal end of a rigid cannula. Proof-of-concept testing was performed using excised whole-mount and hemilarynx human tissue aerodynamically driven into self-sustained oscillation, with systematic variation of the superior-inferior positioning of the vocal fold collision sensor. In the hemilarynx experiment, signals from the pressure sensors were synchronized with an acoustic microphone, a tracheal-surface accelerometer, and two high-speed video cameras recording at 4000 frames per second for top-down and en face imaging of the superior and medial vocal fold surfaces, respectively. As expected, the intraglottal pressure signal exhibited an impulse-like peak when vocal fold contact occurred, followed by a broader peak associated with intraglottal pressure build-up during the de-contacting phase. As subglottal pressure was increased, the peak amplitude of the collision pressure increased and typically reached a value below that of the average subglottal pressure. Results provide important baseline vocal fold collision pressure data with which computational models of voice production can be developed and in vivo measurements can be referenced.

Intraglottal aerodynamic pressure and energy transfer in a self-oscillating synthetic model of the vocal folds

“…The onset pressure and flow rate of the synthetic model were higher than physiological values 67 . This behavior has been observed in prior investigations with hemilaryngeal configurations 57,68,69 . In addition, a relatively high medial prephonatory compression was required to get robust contact in the synthetic models, which also increased the onset pressure and the flow rate.…”

Direct Measurement and Modeling of Intraglottal, Subglottal, and Vocal Fold Collision Pressures during Phonation in an Individual with a Hemilaryngectomy

“…Essentially, if the signals captured by two adjacent pressure sensors are in phase and correlated, then they are both positioned in the same location-supraglottally, subglottally, or intraglottally. If the two sensor signals have waveshapes distinct from each other, their difference signal, polarity, and degree of correlation help confirm that one of the sensors is positioned as desired between the glottis and in the strike zone of collision during phonation [12,13].…”

“…Expectations with respect to the waveform shape of the intraglottal pressure signal come from numerical models of phonation [14][15][16][17][18][19][20], self-oscillating physical models of synthetic vocal fold-like material [12,14,21], aerodynamically driven excised larynges or hemilarynx models [13,[22][23][24][25][26][27][28], and in vivo animal models [29]. For example, in a hemilarynx model, the superior-inferior position of a pressure sensor was systematically varied as the model was driven into self-sustained oscillation with an external airflow source [13]. The position of the sensor was confirmed to be in the strike zone of vocal fold collision using a dual-imaging technique that provided en face imaging of the medial vocal fold surface and top-down imaging of the vibrating vocal fold.…”

“…The side with the vocal fold removed is then surgically reconstructed to form a scar band that is medialized using implantable materials (e.g., adipose tissue) so that the vibrating contralateral vocal fold can achieve glottal closure during phonation. The reconstructed larynx is analogous to the excised hemilarynx setup that has been previously employed to study phonatory physiology, e.g., [13,[33][34][35]. Many of these patients have perceptually typical conversational voices that are much improved compared with their pre-surgical condition, when they often exhibit insufficient glottal closure that produces excessively inefficient voice production and a breathy voice quality [36].…”

“…The primary aim of this paper is to report on the first in vivo application of a recently developed transoral, dual-sensor intraglottal/subglottal pressure (ISP) probe [12,13] in such an individual with a hemilaryngectomy. In these individuals, the tip of the ISP probe is designed to rest against the surgically medialized scar band to yield stable and reliable collision pressure measurements of the medial surface of the contralateral vocal fold (essentially acting as an excised hemilarynx configuration).…”