Purpose Digital kymography and vocal fold curve fitting are blended with detailed symmetry analysis of kymograms to provide a comprehensive characterization of the vibratory properties of injured vocal folds. Method Vocal fold vibration of twelve excised canine larynges was recorded under uninjured, unilaterally injured, and bilaterally injured conditions. Kymograms were created at 25%, 50%, and 75% of the vocal fold length, and vibratory parameters were compared quantitatively among conditions and studied with respect to right-left and anterior-posterior symmetries. Results Anterior-posterior amplitude asymmetry was found in the bilateral condition. The unilateral condition showed significant right-left amplitude asymmetry, and it showed the lowest right-left phase symmetry among the conditions. In condition comparisons, vertical phase difference did not show significant differences among conditions, while amplitudes were significantly different among conditions at all line scan positions and most vocal fold lips. Significant differences in frequency were found among the conditions at all four vocal fold lips, with the bilateral condition exhibiting the greatest frequency. Conclusion Digital kymography and curve fitting provide detailed information about the vibratory behavior of injured vocal folds. Awareness of vibratory properties associated with vocal fold injury may aid in diagnosis, and the quantitative abilities of digital kymography may allow for objective treatment selection.
OBJECTIVES The purpose of this study was to investigate the effect of vocal fold adduction on voice quality in an ex vivo larynx model. STUDY DESIGN Prospective, repeated-measures experiments. METHODS Ten excised canine larynges were mounted on an excised larynx phonation system and measurements were recorded for three different vocal fold adduction levels. Acoustic perturbation measurements of jitter, shimmer, and signal-to-noise ratio (SNR) were calculated from recorded radiated sound histories. RESULTS Ex vivo experiments indicated that statistically significant increases in the means of jitter (p=0.005), shimmer (p=0.002), and SNR (p=0.011) measures decreased with respect to vocal fold adduction as the independent variable. Theoretical results showed that the DC and AC component of glottal area increased monotonically with prephonatory glottal area. CONCLUSIONS Acoustic perturbation increased with the degree of vocal fold abduction. Ex vivo larynx measurements suggested that a hyperadducted state may be acoustically best. This may be explained theoretically by an increase in DC/AC ratio as the prephonatory area is increased.
Objective To investigate the effect of vocal fold injury location on vibratory amplitude and lateral phase difference. Study design Repeated measures with each excised canine larynx serving as own control. Setting Basic science study conducted in university laboratory. Methods Vocal fold vibration of excised canine larynges was recorded with a high speed camera before and after inducing vocal fold injury at one of five locations: anterior, middle, posterior, medial, or superior. Medial and superior injuries were created within the middle third of the vocal fold. Five larynges were used for each of the five injury locations. Kymography was performed at the midpoint of the vocal folds for each video. Pre- and post-injury vibratory amplitude and lateral phase difference were compared for each location. Results The anterior and medial injuries produced consistent decreases in vibratory amplitude. Middle and posterior injuries may slightly decrease amplitude. Superior injuries seemed to have no effect on amplitude. Anterior and medial injuries induce phase asymmetry between the right and left vocal folds. Middle injuries appeared to affect phase difference slightly, whereas posterior and superior injuries had no effect. Conclusion Injury to the anterior or medial portions of the vocal fold may be most likely to cause abnormal vocal fold vibration. Using caution in these locations during phonosurgery may favor superior post-operative vocal outcomes.
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