Effect of Subglottic Stenosis on Vocal Fold Vibration and Voice Production Using Fluid–Structure–Acoustics Interaction Simulation

Abstract

An in-house 3D fluid–structure–acoustic interaction numerical solver was employed to investigate the effect of subglottic stenosis (SGS) on dynamics of glottal flow, vocal fold vibration and acoustics during voice production. The investigation focused on two SGS properties, including severity defined as the percentage of area reduction and location. The results show that SGS affects voice production only when its severity is beyond a threshold, which is at 75% for the glottal flow rate and acoustics, and at 90% for the vocal fold vibrations. Beyond the threshold, the flow rate, vocal fold vibration amplitude and vocal efficiency decrease rapidly with SGS severity, while the skewness quotient, vibration frequency, signal-to-noise ratio and vocal intensity decrease slightly, and the open quotient increases slightly. Changing the location of SGS shows no effect on the dynamics. Further analysis reveals that the effect of SGS on the dynamics is primarily due to its effect on the flow resistance in the entire airway, which is found to be related to the area ratio of glottis to SGS. Below the SGS severity of 75%, which corresponds to an area ratio of glottis to SGS of 0.1, changing the SGS severity only causes very small changes in the area ratio; therefore, its effect on the flow resistance and dynamics is very small. Beyond the SGS severity of 75%, increasing the SGS severity, leads to rapid increases of the area ratio, resulting in rapid changes in the flow resistance and dynamics.

Effect of Subglottic Stenosis on Expiratory Sound Using Direct Noise Calculation

“…The base thickness of the vocal fold (thickness of the lateral surface) was fixed at 0.9 cm. The geometry of the SGS was based on a previous study [17] and was defined by a sinusoidal function of one wavelength. The vertical (inferior-superior) thickness of the SGS at the base remained constant at 1 cm, while the severity of the SGS was adjusted by modifying the amplitude of the sinusoidal function.…”

“…Although the SGS is commonly modeled using simplified geometries such as axisymmetric [17,18]) or two-dimensional [19] shapes, irregular shapes of the SGS are commonly observed in clinical examination. Compared to the axisymmetric SGS, the irregularly shaped SGS is less likely to produce whistling tones, likely due to the irregularities in the shape that disrupt the orderly flow structures necessary for whistling to occur.…”

“…A few recent studies on SGS have focused on its influence on voice production [17][18][19]. A common finding was that SGS had no significant effect on the glottal flow until high severity (where the area blockage was 80%~90%).…”

Special Issue on Computational Methods and Engineering Solutions to Voice II

“…Li et al [6] suggest a FEM model for the investigation of unilateral vocal fold paralysis to improve surgical outcomes. Bodaghi et al [7] study the effect of subglottic stenosis on vocal fold vibration and voice production, considering the entire fluid-structure-acoustic interaction process in a three-dimensional model. Schoder et al [8] investigate the aero acoustic sound source, applying the so-called Perturbed Convective Wave Equation (PCWE).…”

Subject-Specific Computational Fluid-Structure Interaction Modeling of Rabbit Vocal Fold Vibration

“…Many lessons have been learned from these insightful studies, including the vibratory characteristics of the vocal fold tissue, the pulsatile jet flow behavior, the transfer of momentum and energy from the flow to the solid, and the multi-faceted effects of the geometric and material properties. Acoustic wave propagation and interaction with the vocal fold were sometimes included in the computational model as well [ 5 , 14 , 15 ]. In addition to computational studies, there have also been many experimental studies of the FSI process of vocal fold using mechanical models or excised larynges [ 16 - 22 ].…”