The influence of the low-frequency transcutaneous electrical nerve stimulation application moment in vocal quality of dysphonic women

Abstract

Objective: to compare the immediate effects of low-frequency TENS employment on vocal quality in women with behavioral dysphonia before and after vocal exercises. Methodology: 30 women (mean = 31.3 years old), diagnosed with behavioral dysphonia received low-frequency TENS before (TENS + VE Group) and after vocal exercises (VE + TENS Group) with a 1-week washout. They had their sustained vowel/a/and running speech recorded before and after each procedure for auditory-perceptual analysis and acoustic measures. The low-frequency TENS parameters applied were symmetrical biphasic quadratic pulse, 200 µs phase, 10 Hz frequency, intensity on the motor threshold, and the electrodes were positioned on the submandibular and superior fibers of the trapezius muscle region. The vocal exercises: tongue trill, humming, finger kazoo, and water resistance therapy were performed totalizing 20 min. Results: intragroup analysis of sustained vowel/a/showed reduction in both groups of strain parameter and increased the breathiness; only VE + TENS Group increased the instability parameter, decreased fundamental frequency, and increased in SPI values; the running speech analysis showed an increase in the overall degree, roughness, and breathiness parameters. However, in VE + TENS Group, there was a statistically significant decrease in the intensity of the strain and an increase in breathiness. The acoustic measures showed that VE + TENS Group had a higher variation than TENS + VE Group regarding NHR. Conclusion: vocal exercises followed by low-frequency TENS have more immediate positive effects on voice quality than the low-frequency TENS followed by vocal exercises. This is a preliminary immediate effects study, and these effects could be verified through long-term assessments.