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Experimental and Computational Study of Intraglottal Pressure Distributions for Vocal Polyps

Rahiminejad Ranjbar, Leila
http://orcid.org/0000-0002-9888-0485
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525409866987658

Abstract Details

, Master of Science, University of Toledo, Mechanical Engineering.
This study focuses on the effects of unilateral sinusoidal-shaped polyps on air pressure on the surface of a model of human vocal folds. Both experimental and numerical methods were used to obtain air pressures on the models. The vocal fold model used for this research is a previously developed model called M6, which is an asymmetric, three-dimensional physical model of the larynx. M6 is 7.5 times larger than life size and has a symmetrical sinusoidal glottal surface profile with an asymmetrical upstream configuration following the anatomy of the trachea and inferior larynx. The glottis has a maximum glottal width of 0.16 cm (real life size) at the mid-coronal section. To capture the e¿ects of polyp lesions, two sessile polyp-like “growths” - spherical caps - of height 0.06 cm and 0.14 cm (real life size) were placed unilaterally. Air pressure was measured at three rows of 14 pressure taps, located in the inferior to superior parts on the vocal fold surface at locations of the anterior (1/4), middle (1/2), and posterior (3/4) of the anterior-posterior span (1.2 cm). Three glottal angles (10° convergent, 0° uniform, and 10° divergent), three polyp conditions (no polyp, the protrusion of 0.06 cm, and the protrusion of 0.14 cm) and a range of transglottal pressures were used to obtain air pressure distributions. The lesions were placed in the medial center of the vocal fold surface (anteriorly-posteriorly and inferiorly-superiorly). For each con¿guration, transglottal pressures of 0.0981, 0.491, 1.742 and 2.453 kPa (i.e., 1, 5, 15 and 25 cm H2O) were used. All the cases were considered with the presence of the arytenoid cartilage in the posterior position (with no airflow through the posterior glottis). The empirical pressures were compared to computational results obtained using the CFD software package ANSYS FLUENT and assuming laminar flow conditions. The results indicated that vocal folds’ pressure distributions varied according to the glottal angle and the presence and size of the polyp lesions. The effects of lesions were considerable in the middle row pressure taps on both sides of the glottis. It was observed that the pressure increased upstream of the lesion and decreased downstream of the lesion. The increase and subsequent decrease in pressure around the polyp creates a non-uniform surface pressure on the vocal folds that was not observed for the healthy glottis. In addition, the pressure changes are highly asymmetrical on the lesion side and non-lesion side of the glottis, creating an asymmetric pressure variation that may alter the vibratory patterns of the vocal folds. This pressure difference also exists in comparing anterior-posterior sections with the mid-coronal section and may turn the acoustic waves into third and fourth modes of vibration. The expected consequence of the pressure distribution changes, along with the asymmetric mass and contour of the vocal folds, would be cycle to cycle variation in period and glottal airflow, giving rise to vocal roughness qualities. The pressure changes due to polyps was largely localized; the pressure differences between a normal glottis and one with a polyp were much less for the pressure taps not at midline (further from the lesions). The large lesion (0.14 cm) caused steeper and higher pressure increases in the local area of the polyps. The experimental study showed higher pressure gradients compared with the computational results. This difference attributed to small differences between the computational and experimental models of the glottis and possible transitional flow past the larger polyp for large transglottal pressures. However, no independent study was conducted to evaluate the validity of the laminar flow assumption for flow conditions considered in this study.
Abdollah A. Afjeh (Committee Co-Chair)
Ronald C. Scherer (Committee Co-Chair)
Sorin Cioc (Committee Member)
135 p.
Biomechanics; Mechanical Engineering
Intraglottal Pressure, Pressure Distribution, Vocal Polyps, Vocal Folds, Phonation

Recommended Citations

Citations

  • Rahiminejad Ranjbar, L. (2018). Experimental and Computational Study of Intraglottal Pressure Distributions for Vocal Polyps [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525409866987658

    APA Style (7th edition)

  • Rahiminejad Ranjbar, Leila. Experimental and Computational Study of Intraglottal Pressure Distributions for Vocal Polyps. 2018. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525409866987658.

    MLA Style (8th edition)

  • Rahiminejad Ranjbar, Leila. "Experimental and Computational Study of Intraglottal Pressure Distributions for Vocal Polyps." Master's thesis, University of Toledo, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525409866987658

    Chicago Manual of Style (17th edition)

toledo1525409866987658
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This open access ETD is published by University of Toledo and OhioLINK.