Effect of Voice Therapy Using Semioccluded Vocal Tract

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Effect of Voice Therapy Using Semioccluded Vocal Tract Exercises in Singers and Nonsingers With Dysphonia Mami Kaneko, Yoichiro Sugiyama, Shigeyuki Mukudai, and Shigeru Hirano, Kyoto, Japan Summary: Objectives. Voice therapy with semioccluded vocal tract exercises (SOVTE) has a long history of use in singers and nonsingers with dysphonia. SOVTE with increased vocal tract impedance leads to increased vocal efficiency and economy. Although there is a growing body of research on the physiological impact of SOVTE, and growing clinical sentiment about its therapeutic benefits, empirical data describing its potential efficacy in singers and nonsingers are lacking. The objective of the current study is to evaluate vocal tract function and voice quality in singers and nonsingers with dysphonia after undergoing SOVTE. Methods. Patients who were diagnosed with functional dysphonia, vocal fold nodules and age-related atrophy were assessed (n = 8 singers, n = 8 nonsingers). Stroboscopic examination, aerodynamic assessment, acoustic analysis, formant frequency, and self-assessments were evaluated before and after performing SOVTE. Results. In the singer group, expiratory lung pressure, jitter, shimmer, and self-assessment significantly improved after SOVTE. In addition, formant frequency (first, second, third, and fourth), and the standard deviation (SD) of the first, second, and third formant frequency significantly improved. In the nonsinger group, expiratory lung pressure, jitter, shimmer, and Voice Handicap Index-10 significantly improved after SOVTE. However, no significant changes were observed in formant frequency. Conclusions. These results suggest that SOVTE may improve voice quality in singers and nonsingers with dysphonia, and SOVTE may be more effective at adjusting the vocal tract function in singers with dysphonia compared to nonsingers. Key Words: Semioccluded vocal tract−Singers−Nonsingers−Formant frequency−Vocal tract.

INTRODUCTION Functional problems with voice are significant contributors to dysphonia. These issues are related to vocal behavior, leading to negative habits and inadequate voice use.1,2 Minor tissue changes, such as vocal fold nodules, that directly result from vocal misuse or trauma to the vocal folds from phonatory behavior can also be categorized as functional dysphonia (FD).2 Organic dysphonia, such as vocal fold atrophy, is sometimes linked to excess muscular tension or laryngeal hyperfunction, and may be compensatory. It is assumed that extrinsic muscles that raise the larynx also affect the way in which the vocal fold vibrates. This causes excessive tension on the vocal tract and reduces voice quality. It is thus important to treat excess tension to resolve functional problems. Semioccluded vocal tract exercises (SOVTE) have long been used in voice clinics throughout the world as a therapeutic approach to reduce excessive tension on the vocal tract3,4 and facilitate resonant voice quality.5 These exercises promote a voice quality that is neither breathy nor pressed, a characteristic that has been regarded as the goal Accepted for publication June 26, 2019. The content of this manuscript was presented at the Voice Foundation’s 48th Annual Symposium, 2019. Financial Disclosure: None. Conflicts of Interest: None. From the Department of Otolaryngology − Head and Neck Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan. Address correspondence and reprint requests to Mami Kaneko, Department of Otolaryngology − Head & Neck Surgery, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto 602-8566, Japan. E-mail: [email protected] Journal of Voice, Vol. &&, No. &&, pp. &&−&& 0892-1997 © 2019 The Voice Foundation. Published by Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jvoice.2019.06.014

of clinicians specializing in voice care.6,7 In addition, for professional voice users, SOVTE help to engage the breathing mechanisms during warm-ups before performances.8 Titze5 utilized computer simulation to support the use of semioccluded vocal tract techniques, such as resonance tubes, voiced fricatives, and lip or tongue trills, to match the input impedance of the vocal tract to the glottal impedance for more efficient phonation. This impedance match may be achieved by lengthening or semiocclusion of the vocal tract at the lips or by adjustments to the size of the epilarynx directly above the vocal folds.9 By doing this, the reactive portion of the vocal tract impedance (or inertive reactance) can be maximized and is able to return energy to the vibrating vocal folds for self-sustained oscillation.10,11 Titze and Laukkanen’s12 calculations with a computer model suggest that the benefits of an artificially lengthened vocal tract are maximized when there is also a constriction at the epilarynx. Anecdotal reports and some clinical studies have reported a sensation of easier phonation after practicing with a resonance tube even for a short period of time.12−14 Vocal tract shape changes during SOVTE have been investigated through CT,15,16 magnetic resonance imaging,17 and with flexible laryngeal endoscopy to evaluate hypopharyngeal and laryngeal changes.18 When pre- and post-SOVTE conditions were compared, it was shown that the total volume of the vocal tract was considerably larger after phonation into a tube.15−17 Several voice training or therapy techniques involve what is often referred to as a “semi-occluded vocal tract,” such as vocal function exercises (VFE)19; resonant voice therapy7,20; the use of fricatives, trills, or nasals3,8; or water resistance

ARTICLE IN PRESS 2 therapy.21 Many studies have focused on SOVET for nonsinger dysphonia, which was conducted for a certain period of SOVTE, such as 6-week treatment. Roy22 assessed the functional effects of vocal hygiene and VFE for 6-week period in 58 randomly chosen voice-disordered teachers. Results suggested that VFE should be considered a beneficial treatment for voice disorders. Roy et al23 conducted a randomized clinical trial with 64 teachers with voice disorders and found that resonance therapy for 6 weeks was as an effective treatment alternative for voice problems in teachers. In a recent randomized controlled trial, Kapsner-Smith et al24 demonstrated that a 6-week therapeutic program for dysphonia, based on flow-resistant tube exercises (stirring straw phonation), resulted in significantly greater improvement in Voice Handicap Index (VHI) scores compared to control group scores. The long-term effects of SOVTE in dysphonia singers have yet to be evaluated. Dastolfo-Hromack et al25 conducted a retrospective study in which they performed singing voice therapy in 51 patients and demonstrated that Singing VHI (SVHI)-10 scores decreased following singing voice therapy. Chernobelsky26 reported on the utilization of laryngeal massage and vocal hygiene in 28 classical singers with nodules. It was concluded that physiologically correct singing leads only to the temporary disappearance of soft nodules and does not promote the resolution of hard nodules. However, the effect of voice therapy in singers with dysphonia has not been sufficiently investigated and various voice therapies have been tried. According to the source-filter theory, the vocal folds produce a sound source, with the vocal tract serving as a filter to modify this source energy. The source-filter theory of speech production provides a foundation that permits inferential assessment of changes in vocal tract length and laryngeal position. This theory states that the energy from a sound source is modified by a filter or set of filters. Any change in the shape of the vocal tract results in altered formants. A formant is defined as “a resonance of the vocal tract.”27 Each formant can be described by its center frequency (the formant frequency) and its bandwidth (a measure of the breadth of energy in the frequency domain). In general, formant frequency locations for vowels are affected by three factors: the length of the pharyngeal-oral tract, the location of constrictions in the tract, and the degree of narrowness of the constrictions. In short, as the vocal tract increases in length, the average formant frequencies are lowered. Therefore, a shorter vocal tract produces resonance changes characterized by elevated formant frequencies; conversely, a longer tract produces lower formants.27 The effect of SOVTE in singers compared to nonsingers with dysphonia has not been sufficiently evaluated. The objective of the current study was to evaluate vocal tract function and voice quality in singers and nonsingers with dysphonia after undergoing therapy with SOVTE.

Journal of Voice, Vol. &&, No. &&, 2019

MATERIALS AND METHODS Subjects In this study, 16 patients with FD, vocal fold nodules, or atrophy were treated with SOVTE, and the vocal outcomes were analyzed retrospectively. The singer group has eight subjects and they were analyzed with FD (three), vocal fold nodules (two), and age-related atrophy with compensatory laryngeal hyperfunction (three). They were aged 19−74 years (mean age, 64 years; four women and four men). As music genre in singer group, there were six classical music and two pop music. The nonsinger group has eight subjects and they were analyzed with FD (three), vocal fold nodules (two), and age-related atrophy (three) with compensatory laryngeal hyperfunction. They were aged 22−81 years (mean age, 60 years; five women and three men). They do not have any history of singing as hobbies, nor professional. Physiological or functional problems were evaluated by stroboscopic examination and vocal assessments. Each stroboscopic examination was reviewed and diagnosed by a board-certified laryngologist. The patients who were diagnosed with vocal fold nodules, vocal fold atrophy with functional problems, or FD were included in this study and underwent voice therapy. No patient had a history of neurologic disease, respiratory disease, or smoking. The subjects presented with stable health conditions during the treatment period. Procedures Voice therapy consisted of vocal hygiene and vocal education regarding the physiology and functional problems of the larynx and voice, and SOVTE. In the singer group, SOVTE voice therapy was divided into three sections: (1) respiratory support, (2) resonant exercises, and (3) application of the techniques to singing. (1) To establish respiratory support, water resistant therapy, tube phonation, or lip trills were tried with three- to five-note descending scales or small intervals. (2) For resonant exercises, to impart the prominent feature of maximizing resonance and air flow, sustained /o/ vowels or /m/, /n/ with vowels were tried with three- to five-note descending scales or small intervals. Technical exercises were then administered such as messa di voce (eg, increasing intensity), the symbiotic relationship between flow phonation and resonance (ie, vocal placement), and register transitions. (3) The application of these techniques to singing consisted of awareness of auditory and tactile sensation during singing voice production. For example, singers were instructed to sing nursery song slowly, focusing on deep abdominal support and the forward focus energy. When they mastered it, they proceed to their professional song. SOVTE for nonsingers followed the same strategy; however, for the application of techniques, the goal was to transfer them to running speech. Nonsingers proceeded the routine phrases such as numbers or days of the week keeping deep abdominal support and the forward focus

ARTICLE IN PRESS Mami Kaneko, et al

Voice Therapy With SOVTE

energy. When they mastered them, they proceeded to running speech. Approximately 12-week-long sessions of behavioral voice therapy were performed in both groups (about six sessions total). These particular exercises were selected because they are putatively designed to manage many aspects of voice production, including an artificially lengthened vocal tract, laryngeal tension, breath support, voice onset, and resonance attributes, which are suitable for dysfunctional voice. Assessment Vocal outcomes were evaluated before and after SOVTE. Aerodynamic assessment, acoustic analysis, stroboscopic examinations, and VHI-10/SVHI-10 were performed. Stroboscopic examination was performed using a digital video stroboscopy system with flexible endoscope, Digital Laryngeal Strobe LS-H10 (Nagashima Co., Osaka, Japan). Aerodynamic assessment, which included mean flow rate (MFR), expiratory lung pressure using the airway interruption method, and intensity were examined with a phonation analyzer (PS-77E, Nagashima Co., Osaka, Japan). Acoustic analyses evaluated jitter and shimmer using a Multi-Dimensional Voice Program (Model 5105; KayPENTAX) with [a:] vowel. All acoustic recordings were made using a personal computer (MDVP advanced software, 44.1 kHz sampling frequency). Formant analysis was performed by downsampling speech used in the MDVP to 11,025 Hz. The formant analysis used the linear predictive coding method, and the filtration degree was set at 12. VHI is a test battery that has been statistically validated. This instrument, completed before and after voice therapy by the patient, permits an understanding of the handicapping nature of the voice disorder as perceived by the patient. The 30-item VHI examines self-perceived voice severity as related to functional, physical, and emotional issues.28,29 The VHI-10 is a 10-question adaption of the original VHI. Rosen et al used item analysis and clinical consensus results to select the most robust items from the VHI from which to form the VHI-10. They suggested that the VHI-10 is a powerful representation of the VHI that takes less time for the patient to complete without a reduction in validity. Thus, the VHI-10 can replace the VHI as a tool for quantifying a patient’s perception of their voice handicap.30 In the present study, the VHI-10 was evaluated. Statistical test Statistical tests using data obtained before and after voice therapy were completed for each parameter. Significant differences were reported at the alpha level of 0.05. All reported P values were two sided. A P value of