Effects of Respiratory Lung Volume Training on Speech Breathing, Voice, and Vocal Function: A Randomized Controlled Trial

Purpose: The purpose of this randomized controlled trial was to determine the short- and long-term effects of Respiratory Lung Volume Training (RLVT) on speech breathing and voice in people with primary muscle tension dysphonia (pMTD). Method: Twenty-four participants with pMTD were randomized to either RLVT or control training (ConT) and completed six 1-hr training sessions. Increased lung volume initiations and terminations were targeted in RLVT using real-time visual biofeedback of lung volumes, whereas the ConT condition implemented a sham Expiratory Muscle Strength Trainer (placebo). Respiratory inductive plethysmography was used to measure speaking lung volumes before and after training. Voice and vocal function outcomes included acoustic measures, auditory-perceptual listener ratings, and self-ratings of speaking effort and impact of the voice disorder. Long-term follow-up assessments were completed for the RLVT condition. Results: Increases in lung volume initiation, termination, excursion, and amount of lung volume used per syllable were all significantly greater after RLVT than after ConT. All increases in respiratory outcome measures were maintained at 3 and 6 months posttraining except for lung volume excursion, which was significantly higher than baseline levels at 6 months but not 3 months posttraining. Acoustic and auditory-perceptual voice severity also showed significantly greater improvement after RLVT than after ConT with gains maintained for both follow-ups. Relative to vocal function, whereas speaking effort was significantly lower after RLVT than after ConT, both conditions produced similar and significant reductions in self-rated voice handicap. Improvements in these vocal function measures were maintained at long-term follow-up timepoints. Conclusions: Speech breathing, voice, and speaking effort outcomes showed significantly greater improvement after RLVT than after ConT in this group of participants with pMTD, with improvement maintained at 6 months post-RLVT. The higher levels of lung volume targeted in RLVT may promote more efficient vocal behavior through functional and mechanical respiratory–laryngeal interactions while decreasing speaking effort.