title: Characterizing liquid redistribution in a biphasic vibrating vocal fold using finite element analysis.
abstract: OBJECTIVE
  Vocal fold tissue is biphasic and consists of a solid extracellular matrix skeleton swelled with interstitial fluid. Interactions between the liquid and solid impact the material properties and stress response of the tissue. The objective of this study was to model the movement of liquid during vocal fold vibration and to estimate the volume of liquid accumulation and stress experienced by the tissue near the anterior-posterior midline, where benign lesions are observed to form.
  
  
  METHODS
  A three-dimensional biphasic finite element model of a single vocal fold was built to solve for the liquid velocity, pore pressure, and von Mises stress during and just after vibration using the commercial finite element software COMSOL Multiphysics (Version 4.3a, 2013, Structural Mechanics and Subsurface Flow Modules). Vibration was induced by applying direct load pressures to the subglottal and intraglottal surfaces. Pressure ranges, frequency, and material parameters were chosen based on those reported in the literature. Postprocessing included liquid velocity, pore pressure, and von Mises stress calculations as well as the frequency-stress and amplitude-stress relationships.
  
  
  RESULTS
  Resulting time-averaged velocity vectors during vibration indicated liquid movement toward the midline of the fold, as well as upward movement in the inferior-superior direction. Pore pressure and von Misses stresses were higher in this region just after vibration. A linear relationship was found between the amplitude and pore pressure, whereas a nonlinear relationship was found between the frequency and pore pressure.
  
  
  CONCLUSIONS
  Although this study had certain computational simplifications, it is the first biphasic finite element model to use a realistic geometry and demonstrate the ability to characterize liquid movement due to vibration. Results indicate that there is a significant amount of liquid that accumulates at the midline; however, the role of this accumulation still requires investigation. Further investigation of these mechanical factors may lend insight into the mechanism of benign lesion formation.
authors.affiliation: Division of Otolaryngology - Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Anton A
authors.initials: AA
authors.lastname: Kvit
authors.affiliation: Division of Otolaryngology - Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Erin E
authors.initials: EE
authors.lastname: Devine
authors.affiliation: Division of Otolaryngology - Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin. Electronic address: jjjiang@wisc.edu.
authors.forename: Jack J
authors.initials: JJ
authors.lastname: Jiang
authors.affiliation: Division of Otolaryngology - Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Vamos
authors.affiliation: Division of Otolaryngology - Head and Neck Surgery, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Chao
authors.initials: C
authors.lastname: Tao
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D045604:Extracellular Fluid / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D008953:Models, Anatomic; D008954:Models, Biological; D009038:Motion; D010699:Phonation; D011312:Pressure; D013314:Stress, Mechanical; D013997:Time Factors; D014732:Vibration; D014827:Vocal Cords / Q000033:anatomy & histology / Q000502:physiology*
keywords: Benign lesions; Biomechanics; Finite element analysis; Vocal folds