title: Variability of electroglottographic glottal closed quotients: necessity of standardization to obtain normative values.
abstract: OBJECTIVE
  To demonstrate the variability of electroglottographic measurements of the glottal closed quotient (GCQ) in normal subjects by the calculation method used, fundamental frequency, and intensity.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Tertiary university-based referral center.
  
  
  METHODS
  Twenty healthy male volunteers without laryngeal disorder. Three successive sustained productions of the vowel /a/ were performed by each subject. Electroglottographic recordings of GCQ were obtained using the criterion level method, which defines an approximate duration of glottal closure and opening. Glottal closed quotient values were calculated based on criterion levels ranging from 10% to 40%.
  
  
  METHODS
  The extent of correlation between GCQ variation and the mean fundamental frequency and intensity.
  
  
  RESULTS
  As the criterion level increased, a decrease in the mean GCQ was recorded, which was significant with a 10% criterion level increase, up to a critical level of 25%. A significant positive correlation was found between GCQ and the variables of fundamental frequency and intensity.
  
  
  CONCLUSIONS
  This study demonstrated significant effects of the criterion level used, fundamental frequency, and intensity in the determination of normative values of GCQ. Normative values can only be assessed through the standardization of one criterion level reached by consensus.
authors.affiliation: Voice, Biomaterials, and Head and Neck Oncology Research Laboratory, Department of Otorhinolaryngology-Head and Neck Surgery, Georges Pompidou European Hospital, University of Paris V, Paris, France.
authors.forename: Romain E
authors.initials: RE
authors.lastname: Kania
authors.forename: Stéphane
authors.initials: S
authors.lastname: Hans
authors.forename: Dana M
authors.initials: DM
authors.lastname: Hartl
authors.forename: Philippe
authors.initials: P
authors.lastname: Clement
authors.forename: Lise
authors.initials: L
authors.lastname: Crevier-Buchman
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Brasnu
mesh_terms: D000328:Adult; D017097:Electric Impedance; D004576:Electromyography; D005931:Glottis / Q000502:physiology*; D006801:Humans; D008297:Male; D010699:Phonation / Q000502:physiology*; D011446:Prospective Studies; D012016:Reference Values; D014833:Voice Quality