Direct simultaneous measurement of intraglottal geometry and velocity fields in excised larynges.

The Laryngoscope

PubMedID: 24510612

Khosla S, Oren L, Ying J, Gutmark E. Direct simultaneous measurement of intraglottal geometry and velocity fields in excised larynges. Laryngoscope. 2014;124 Suppl 2S1-13.
OBJECTIVES/HYPOTHESIS
Current theories regarding the mechanisms of phonation are based on assumptions about the aerodynamics between the vocal folds during the closing phase of vocal fold vibration. However, many of these fundamental assumptions have never been validated in a tissue model. In this study, the main objective was to determine the aerodynamics (velocity fields) and the geometry of the medial surface of the vocal folds during the closing phase of vibration. The main hypothesis is that intraglottal vortices are produced during vocal fold closing when the glottal duct has a divergent shape and that these vortices are associated with negative pressures.

STUDY DESIGN
Experiments using seven excised canine larynges.

METHODS
The particle imaging velocimetry (PIV) method was used to determine the velocity fields at low, mid-, and high subglottal pressures for each larynx. Modifications were made to previously described PIV methodology to allow the measurement of both the intraglottal velocity fields and the position of the medial aspects of the vocal fold.

RESULTS
At relatively low subglottal pressures, little to no intraglottal vortices were seen. At mid- and high subglottal pressures, the flow separation vortices occurred and produced maximum negative pressures, relative to atmospheric, of -2.6 to -14.6 cm H2 O. Possible physiological and surgical implications are discussed.

CONCLUSIONS
Intraglottal vortices produce significant negative pressures at mid- and high subglottal pressures. These vortices may be important in increasing maximum flow declination rate and acoustic intensity.

LEVEL OF EVIDENCE
N/A. Laryngoscope, 2013.