Larynx under ultra-high subglottal pressure: measure of contact force between vocal folds in excised human larynges
Résumé
Objective: Subglottal pressure is often considered as a clue of vocal abuse, and this parameter is supposed to beat the origin of the phonotraumatism. This study is based on experiments on excised human larynges. Theobjective of this study was to analyze the contact pressure between the vocal folds during phonation and itsrelation with subglottal pressure until very high values.Material and methods: 7 human excised larynges were set on the experimental test-bench. The vocal foldadduction was determined before the tests, using concomitant arytenoid adduction and membranous vocal foldmedialization with Montgomery implants. The subglottal pressure (SGP) increased from 0 to 200 hPa. Thecontact pressure was measured with a pressure sensor placed between the vocal folds, the tracheal airflow andsubglottal pressure were measured 1 cm under the glottis, the electroglottography (EGG) was recorded, as wellas the audio signal (microphone distance: 15cm from the larynx).Results: At the phonation threshold, contact pressure appeared at the same time as the first activity of EGG,before the onset of the glottal cycle, then rapidly increased until a plateau. The maximal values of the contactpressure were very variable between the larynges (range: 0,7-12kPa). This contact pressure was not proportionalto the subglottal pressure.Discussion: These results question the role of subglottal pressure as the main factor of phonotrauma in vocalabuse when glottal configuration is constant. The adduction forces between vocal folds may be more relevant butvery difficult to measure in patients.