The Effects of Respiratory-Based Treatment for Muscle Tension Dysphonia: A Randomized Controlled Trial
Phase: NA
Conditions: Muscle Tension Dysphonia
Sponsor: Syracuse University

Study Title: The Effects of Respiratory Training on Voice 
NCT #: NCT04710862 
Document Title: Protocol Summary 
Document Date: May 25, 2025 
 
 
 
 
 

Participants were recruited from local physicians, speech-language pathologists, 
communication disorder clinics, and ClinicalTrials.gov. Participants were included if 
ages 18 or older, were in good general health per self-report other than the voice 
disorder, with normal pulmonary function, reported problems with their voice that had 
been present for 2 months or longer, were non-smokers, had English as their primary 
language to avoid potential linguistically-based differences in acoustic measures of 
voice, showed adequate corrected or uncorrected vision to read basic graphs and print 
as determined with visual screening, showed no organic or neurologic vocal fold 
pathology per laryngology exam performed and assessed by a laryngologist, were not 
currently receiving voice therapy, did not report a bilateral severe or profound level of 
hearing loss, had a diagnosis of muscle tension dysphonia, showed acoustic dysphonia 
(Cepstral/Spectral Index of Dysphonia) that exceeded normative values for the 
participant’s age and sex, showed one or more patterns of supraglottic activity and 
presence of normal/complete vocal fold closure patterns during laryngoscopy 
examination, and showed evidence of speech breathing abnormalities relative to 
normative values. Prior to scheduling the first visit, general information about the study 
was provided during a telephone screening to determine basic eligibility status, with a 
copy of the consent form emailed or mailed to them for review before the first 
appointment.  
Assessments 
In the initial assessment visit, informed consent was obtained and an initial voice 
questionnaire was completed. For all participants, speech breathing behavior and voice 
acoustic recordings were obtained during a variety of speaking tasks that were 
repeatedly administered to determine performance at baseline, after the training phase, 
and at long-term follow-up timepoints. The primary testing and training phases took 
place over an 8-week period that included two pre-training assessment sessions in 
week 1 (baseline assessments), six training sessions held 1xweek (weeks 2 through 7), 
and two post-training assessment sessions in week 8. Assessment visits were 
approximately 2 hours, and training sessions were approximately one hour. 
Laryngoscopy evaluation was completed in week 1 if not recently performed and with 
recording obtainable through participant’s consent. In addition to the acoustic and 
speech breathing measurement described below, questionnaires were completed at 
each assessment timepoint including the Voice Handicap Index-10 and quantification of 
self-reported speaking effort on a visual analog scale. Participants were provided 
compensation for their time spent during all assessment but not training visits. 
Acoustic recordings were obtained with a digital recording system simultaneously with 
speech breathing recordings. The Computerized Speech Lab (Pentax Medical) was 
subsequently used for all analyses of the acoustic data. To record and display 
respiratory signals, the respiratory InductoTrace system (Ambulatory Monitoring Inc) 

was used, which included placement of transducer bands around the rib cage and 
abdomen to record volume changes associated with inspiration and expiration. 
Procedures for speech breathing calibration and measurement were based on well-
established methods used clinically and in research. Participants performed calibration 
tasks while lung volume was measured with a digital spirometer, noseclip and 
mouthpiece. Subsequent recordings of the change in volume for the rib cage and 
abdomen during speech productions were measured while the participant read a 
passage aloud, providing estimated lung volume levels without the use of the 
spirometer. Participants returned for long-term assessments at 3 and 6-months post-
training. After all short-term sessions were completed (weeks 1-8), control (sham) 
condition participants were subsequently offered the experimental condition (described 
below).  
Training 
Participants with muscle tension dysphonia were randomly assigned to one of two 
conditions: 1) respiratory lung volume training (RLVT) and 2) a control training (CT) 
condition involving a sham training device. For the RLVT condition, after the initial 
assessment sessions, training session 1 addressed instruction and training on 
appropriate speech breathing behavior, the rationale for targeting increased lung 
volume initiation and termination levels, and the targeted movements of the rib cage 
and abdomen. Training sessions 2 through 6 directly trained higher lung volume level 
targets during speech. Specifically, higher levels of lung volume initiation and 
termination were targeted to capitalize on non-muscular forces contributing to speech 
production. Increased frequency of breaths and reduced words per breath group were 
also incorporated into speech training. Training for RLVT included real-time visual 
biofeedback of lung volume levels in graphic form, with signals displayed on a large 
screen monitor and target levels for lung volume initiation and termination 
superimposed on the graphic display. This visual biofeedback was used to enhance 
motor learning of new speech breathing patterns. A hierarchical progression of gradually 
increasing length and complexity of speech was followed throughout training to facilitate 
skill acquisition and transfer of skills, while also incorporating spontaneous speech 
throughout training. A videorecording of one training session was performed for each 
participant using a digital video camcorder and tripod. This was later rated by a 
research team member who did not perform the training to determine fidelity of the 
training to specified protocol goals and stimuli. 
The CT condition provided respiratory-like “training” that was not expected to improve 
speech breathing, and has been used as a control (sham) respiratory condition in prior 
studies. Expiratory muscle strength training (EMST) is among the most frequently 
studied respiratory treatments in studies addressing vocal outcomes and has been 
studied in people with voice disorders. A commercially available device (EMST 150; 

Aspire Products) was purchased in modified form as a sham-EMST device which 
removed the internal spring device that offers expiratory resistance. Multiple studies 
involving general respiratory training have effectively implemented this device with the 
spring removed as a sham respiratory condition that allows for participant blinding. In 
the CT condition, participants performed multiple sets of 5 exhalations each through the 
non-resistive device following a full inspiration, with intervening rest periods between 
each exhalation and longer rest periods between each set. Number of sessions and 
time per session were identical for the CT and RLVT conditions, including pre-training 
and post-training assessment visits. 
A home practice program with homework tracking sheets was completed throughout all 
six training sessions for both the RLVT and CT conditions to facilitate carryover of 
training and equalize home practice time between the two conditions. Additional 
explanation and speech stimuli for a continued home practice program was provided at 
the post-training assessment sessions after RLVT. Participants were encouraged to 
continue structured home practice including tasks associated with daily activities of 
living at least three times a week through the 6-month time period elapsing between 
training completion and the final long-term follow-up session.