Comparative Study of Two Semi-Occluded Vocal Tract Protocols: A Randomized Clinical Trial.

INTRODUCTION

Semi-occluded vocal tract exercises (SOVTEs) are widely used as a therapeutic tool to create flow resistance in the upper airway. The current study was a randomized controlled clinical trial to establish the efficacy of two SOVTE protocols, flow-resistant tube (FRT) and Lessac-Madsen Resonant Voice Therapy (LMRVT). Exploratory investigations included a noninferiority analysis of FRT to the widely adopted therapy protocol (LMRVT), as well as examining the dosing required to improve acoustic measures and subjective ratings.

METHOD

Sixty-seven participants with voice disorder were randomized into one of five groups: 4-week FRT ( = 14), 8-week FRT ( = 19), 4-week LMRVT ( = 15), 8-week LMRVT ( = 5), and control ( = 14). Voice Handicap Index (VHI) and Vocal Fatigue Index scores were collected pre- and posttreatment. Acoustic analysis using the Acoustic Voice Quality Index was completed. We compared VHI between controls and 8-week FRT and LMRVT, adjusting for pre-VHI using linear regression. We examined the efficacy of 4-week protocols relative to controls and conducted a noninferiority comparison of FRT (4 and 8 weeks) to LMRVT (4 and 8 weeks) using 5- and 10-point margins. Finally, we compared the 4- versus 8-week sessions for both therapies.

RESULTS

A statistically significant reduction of VHI in both 8-week FRT relative to controls (-10.60, 95% CI [-19.80, -1.40], = .025) and 8-week LMRVT (-15.74, 95% CI [-29.40, -2.08], = .025) was found. We also found an improvement in 4-week FRT relative to controls (-10.11, 95% CI [-20.03, -0.20], = .046), but the 4-week LMRVT result was not statistically significant ( = .057). FRT was found to be noninferior to LMRVT in terms of VHI using a 10-point margin (FRT - LMRVT: 0.69, 95% CI [-5.76, 7.15], = .01), but not using a 5-point margin ( = .054). There were no statistically significant differences in VHI scores between 4- and 8-week sessions for either therapy.

CONCLUSIONS

Both FRT and LMRVT improved VHI scores relative to controls. FRT was noninferior to LMRVT in terms of VHI scores. There were no statistically significant differences in VHI scores between 4- and 8-week therapy sessions.