Meta-analysis of semi-occluded vocal track exercise studies on acoustic, aerodynamic, and electroglottographic results

Abstract

Objectives: Recently semi-occluded vocal tract exercise (SOVTE) is commonly used in voice clinic and research. This study aimed at investigating the effects of SOVTE on acoustic, aerodynamic, and electroglottographic analysis in patients with dysphonia using meta-analysis. It also examined whether there was differences in the effects by type of voice disorders. Methods: Eighteen studies published between 2000 and 2018 which met the inclusion and exclusion criteria were selected from 9 database. These 18 studies were divided into 37 subjects by SOVTE subtype and dysphonic type. The effect sizes and mean effect sizes of acoustic (fundamental frequency [F0], sound pressure level [SPL], %jitter, %shimmer, noise-to-harmonic ratio [NHR]), aerodynamic (subglottal pressure [Psub], phonation threshold pressure [PTP], glottal airflow, glottal resistance), and electroglottographic (closed quotient [CQ]) analysis were calculated by Hedges' g using standardized mean difference. Results: Based on the results of meta-analysis, SOVTE significantly changed acoustic measures, but did not change aerodynamic measures and CQ. However, when the sub-items of those measures were examined, %jitter, %shimmer, NHR, Psub, PTP, glottal resistance were significantly changed by SOVTE. In addition, the acoustic analysis, %jitter, aerodynamic analysis, Psub, and CQ showed significant differences among the different types of voice disorders. Conclusion: The study shows that SOVTE reduced voice problems measured in acoustic, aerodynamic, and electroglottographic analysis and can be applied for hyperfunctional voice disorders and glottal gap.