title: Preliminary Study of the Open Quotient in an Ex Vivo Perfused Human Larynx.
abstract: OBJECTIVE
  Scientific understanding of human voice production to date is a product of indirect investigations including animal models, cadaveric tissue study, or computational modeling. To our knowledge, direct experimentation of human voice production has previously not been possible owing to its invasive nature. The feasibility of an ex vivo perfused human phonatory model has recently allowed systematic investigation in virtually living human larynges with parametric laryngeal muscle stimulation.
  
  
  OBJECTIVE
  To investigate the association between adductor muscle group stimulation and the open quotient (OQ) (the fraction of the cycle during which the glottis remains open) of vocal fold vibration.
  
  
  METHODS
  An ex vivo perfused human tissue study was conducted at a physiology laboratory. Human larynx recovered from organ donors within 2 hours of cardiac death was used. The study was performed on May 19, 2014; data analysis took place from June 1, 2014, to December 15, 2014.
  
  
  METHODS
  Perfusion with donated human blood was reestablished shortly after cardiac death. Ex vivo perfused human phonation was then achieved by providing subglottal airflow under graded neuromuscular electrical stimulation bilaterally to the intrinsic adductor groups and cricothyroid muscles.
  
  
  METHODS
  Phonation resulting from the graded states of neuromuscular stimulation was evaluated using high-speed vibratory imaging; the OQ was derived through digital kymography and glottal area waveform analysis.
  
  
  RESULTS
  During constant glottal flow, a stepwise increase in adductor muscle group stimulation decreased the OQ. Quantitatively, OQ values decreased with increased stimulation levels from 2 V (OQ, 1) to 5 V (OQ, 0.68) and reached a lower limit of 8 V (OQ, 0.42). Increased stimulation above maximal muscle deformation was unable to affect OQ beyond this lower limit.
  
  
  CONCLUSIONS
  To our knowledge, a negative association between adductor muscle group stimulation and phonatory OQ has been demonstrated for the first time in a neuromuscularly activated human larynx. Further experience with the ex vivo perfused human phonatory model will aid in systematically defining this causal relationship.
authors.affiliation: Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles.
authors.forename: Abie H
authors.initials: AH
authors.lastname: Mendelsohn
authors.affiliation: Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles.
authors.forename: Zhaoyan
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles.
authors.forename: Georg
authors.initials: G
authors.lastname: Luegmair
authors.affiliation: Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles.
authors.forename: Michael
authors.initials: M
authors.lastname: Orestes
authors.affiliation: Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles.
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Berke
mesh_terms: D004558:Electric Stimulation; D005931:Glottis / Q000503:physiopathology*; D006801:Humans; D007734:Kymography; D007821:Laryngeal Muscles / Q000503:physiopathology*; D008954:Models, Biological; D010699:Phonation / Q000502:physiology*; D046509:Tissue Culture Techniques