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Acoustic-Aerodynamic Voice Outcome Ratios Identify Changes in Vocal Function Following Vocal Fold Medialization for
Latané Bullock1, Laura E Toles2, Robert E Hillman3
1Center for Laryngeal Surgery and Voice Rehabilitation, Massachusetts General Hospital, Boston, Massachusetts; Division of Medical Sciences, Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, Massachusetts.
Purpose:
This study aimed to determine whether ratio-based measures that combine acoustic (output) and aerodynamic (input) parameters detect postoperative change in vocal function following vocal fold medialization for unilateral vocal fold paralysis.
Method:
Pre- and postoperative acoustic and aerodynamic measures were analyzed retrospectively from 149 patients who underwent vocal fold medialization for unilateral vocal fold paralysis. A 2 × 2 repeated-measures analysis of variance was conducted for each of four acoustic-aerodynamic ratios-traditional vocal efficiency (VE), sound pressure level to aerodynamic power (SPL/AP), SPL to average airflow (SPL/AFLOW), and SPL to subglottal pressure (SPL/Ps)-to investigate the main effects and interaction of treatment stage and loudness level (comfortable and loud).
Results:
The patient group showed significant postoperative improvements in self reports of vocal function (voice-related quality of life) and clinical auditory-perceptual judgments of dysphonia (consensus auditory-perceptual evaluation of voice). Main effects for both treatment stage and loudness level were statistically significant for all measures except SPL/Ps. There were interaction effects for VE and SPL/AP, suggesting that magnitude of the treatment effect differs based on loudness. SPL/AFLOW had medium-to-large effect sizes in both loudness conditions. There were postoperative changes in SPL/Ps that were dependent on the magnitude of the reduction in AFLOW; as expected, SPL/Ps increased postoperatively in a subgroup that had large postoperative reductions in AFLOW at the comfortable loudness level.
Conclusions:
Acoustic-aerodynamic ratios can aid in tracking changes in vocal function following vocal fold medialization. SPL/AFLOW exhibited the largest effect size, which is expected since a reduction in abnormally high AFLOW typically accompanies the increased modulation of glottal air flow associated with successful vocal fold medialization. Future study is needed to model physiological changes in acoustic-aerodynamic voice outcome ratios across different types of voice disorders.
