ARTICLE IN PRESS The Effects of Expiratory Muscle Strength Training on Voice and Associated Factors in Medical Professionals With Voice Disorders *,†Yuan-Ching Tsai, *ShihWei Huang, *Wei-Chun Che, †Yi-Ching Huang, *,‡Tsan-Hon Liou, and †Yu-Chi Kuo, *,†,‡Taipei, Taiwan

Summary: Objectives. This research used expiratory muscle strength training to explore the factors relevant to medical professionals with voice disorders. The maximal expiratory pressure (MEP) improved, which is measured by the maximal contracting force of expiratory muscles. The expiratory muscle strength increased, which can affect the positive pressure of pulmonary volume, thereby influencing subglottal pressure for speech to change the voice performance and vocal-fold vibration. Methods. Twenty-nine participants with voice disorders who are working in a hospital and who are using their voice for more than 4 hours per day were recruited. The participants were randomly assigned to either the study group (STU) or the control group (CON). All participants underwent aerodynamics analysis, pulmonary function, MEP, and completed a vocal symptoms questionnaire before and after STU was provided. The interventions in the STU were conducted 3 days per week and involved performing 25 expiratory exercises (five cycles, each comprising five breaths) for 5 weeks. The CON did not receive any intervention. Results. The voiceless /S/ expiratory time, symptom questionnaire scores, and MEP were greater in the STU than in the CON (P < 0.05). However, no statistically significant difference in the results of the pulmonary function was observed between the groups. The STU exhibited a greater percentage change in maximal voiced /Z/ phonation and voiceless /S/ expiratory compared with the CON (P < 0.05). Conclusions. The participants’ voiceless /S/ expiratory time, symptom questionnaire scores, and MEP significantly improved after the intervention. Future studies can increase the number of participants, increase the number of study groups, and examine the effectiveness of long-term treatment. Key Words: Expiratory muscle strength training (EMST)–Voice disorder–Maximal expiratory pressure (MEP)–Medical professionals–Self-awareness of vocal symptoms questionnaire.

INTRODUCTION The voice is essential to people’s occupational, recreational, and social lives, and voice performance depends on coordination among the respiratory, phonation, and resonance systems.1 Voice disorders can influence daily communication and, thus, hinder professional and occupational performance. Speaking during breathing requires well incorporations between vocal organs and respiratory function to sufficiently compress subglottal pressure (Ps) for stabilizing sound production and speaking.2 During the speaking, more airflow would be required to support sound production, thus respiratory muscle needs to rapidly perform fine adjustments to maintain a dynamic balance between active and passive air pressures. The active pressure origins form respiratory muscles, including negative pressure of inspiratory muscles and positive pressure of expiratory muscle. The passive pressure is produced by elastic flexibility of thoracic cage.3–6 Accepted for publication September 22, 2015. From the *Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan; †Department of Exercise and Health Science, National Taipei University of Nursing and Health Science, Taipei, Taiwan; and the ‡Graduate Institute of Injury Prevention and Control, Taipei Medical University, Taipei, Taiwan. Address correspondence and reprint requests to Yu-Chi Kuo, Department of Exercise and Health Science, National Taipei University of Nursing and Health Science, No.365, Mingde Rd., Beitou, Taipei, Taiwan 112. E-mail address: [email protected] Journal of Voice, Vol. ■■, No. ■■, pp. ■■-■■ 0892-1997 © 2015 The Voice Foundation. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jvoice.2015.09.012

The respiratory system provides the energy required for sound production, and airflow during respiration is essential for phonation. Impaired coordination between respiratory and laryngeal systems can lead to vocal fatigue when speaking. The rate and forces during the expiratory phase in phonatory respiration must be controlled to maintain smooth and stable airflow, thereby ensuring that Ps is constant and that voice quality is high.3–6 When the respiration system is unable to provide sufficient power for sound production, the laryngeal system overcompensates for this lack of power, causing changes in vocal tissue and in voice quality.7 Like other muscles, the strength and endurance of respiratory muscles can be improved through exercise training.8,9 The purpose of respiratory muscle training is to improve voicing efficiency by strengthening respiratory muscles and reducing laryngeal overcompensation or hyperfunction.7 In a study conducted by Baker, normal participants were divided into two groups that separately underwent 4-week and 8-week respiratory muscle training programs. Both groups exhibited significant improvements in maximal expiratory pressure (MEP) and decreases in the intraoral or mouth pressure/MEP ratio. A significant decrease in the Ps/MEP ratio was observed only in the group that underwent 4 weeks of training. Baker concluded that respiratory muscle training benefits the voice.10 The study conducted by Wingate et al yielded a similar outcome.11 After undergoing 5 weeks of expiratory muscle strength training (EMST), professional voice users exhibited improvements in MEP, the Voice

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Handicap Index (VHI), and Ps when asked to speak loudly. However, Roy et al determined that 6 weeks of EMST exerted no effect on voice performance.7 The effect of respiratory muscle training on the voice performance remains unclear. Therefore, we proposed the present study to investigate the effects of a 5-week EMST intervention on the respiratory system and vocal performance in people with voice disorders. MATERIALS AND METHODS Participants Twenty-nine participants, three men and 26 women, were enrolled in this study (Table 1). All participants were medical professionals recruited from the Shuang Ho Hospital in Taiwan. People who (1) used their voice for more than 4 hours while working,11 (2) were aware of their voice problems, (3) and were generally healthy and had no systemic diseases were included in this study. The criteria for case selection was depended on whether the paticipants had both severe self-awareness of vocal abnormality, and we then matched their ages, genders, maximal phonation time, and self-aware their voice problems in both experimental groups. The participants in this study mostly exhibited hoarseness voice pattern and smaller voice volume. People with respiratory system problems, cardiovascular disease, or oral and laryngeal structural abnormality, as well as

those who were pregnant were excluded. The Institutional Review Board of Taipei Medical University approved this study. The 29 participants were randomly assigned to one of two groups, the study group (n = 15) and the control group (n = 14). The study group underwent an expiratory muscle training program for 5 weeks, whereas the control group received no intervention. All participants were administered a voice-use questionnaire and were subjected to pulmonary analysis and an expiratory muscle strength test before and after the intervention. Intervention An expiratory muscle strength trainer (Figure 1) was applied in expiratory muscle training, and the resistance pressure was kept at the intensity of 75% MEP for all participants in the study group. According to the evidence of training effects in skeletal muscle tissue, this intensity is close to the maximal loading of muscle strengthening.6,9 The training protocol entailed performing 25 expiratory exercises (divided into five cycles) per day for 3 days per week for 5 consecutive weeks.7,11 To ensure that only oral expiration was performed, a nose clip was used during expiratory muscle training (Figure 2).11,12 The participants inhaled maximally, sealing the mouthpiece of the device firmly, and then exhaled as forcefully as possible. The intensity had to reach 75% MEP and be sustained for 2 seconds. To increase the efficacy of expiratory muscle training, the MEP values were adjusted every

TABLE 1. Basic Characteristics of the Participants (n = 29) Variable Sex† Male Female Age* 20–24 years 25–29 years 30–34 years 35–39 years 40–44 years Education† College University Graduate degree Work experience* 0–4 years 5–9 years 10–14 years 15–19 years Work environment Open area Closed area Time at work spent talking 4–6 hours 6–8 hours * Mann-Whitney U test (P < 0.05). † Pearson chi-square test (P < 0.05).

Study (%) (n = 15)

Control (%) (n = 14)

1 (6.7) 14 (93.3)

2 (14.3) 12 (85.7)

1 (6.7) 8 (53.3) 5 (33.3) 1 (6.7) 0

2 (14.3) 7 (50.0) 2 (14.3) 2 (14.3) 1 (7.1)

1 (6.7) 9 (60.0) 5 (33.3)

2 (14.3) 7 (50.0) 5 (35.7)

8 (53.3) 6 (40.0) 1 (6.7) 0

5 (35.7) 6 (42.9) 2 (14.3) 1 (7.1)

10 (66.7) 5 (33.3)

7 (50.0) 7 (50.0)

4 (26.7) 11 (73.3)

8 (57.1) 6 (42.9)

P 0.508

0.481

0.883

0.234

ARTICLE IN PRESS Yuan-Ching Tsai et al

Expiratory Muscle Strength Training and Voice Disorders

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Measurement of maximum phonation time (MPT) is chosen to reflect respiratory and vocal function of the participants.

FIGURE 1. Device used in expiratory muscle strength training.

Self-awareness of vocal symptoms questionnaire The questionnaire was designed specifically for this study by the first author and was revised by two experienced speech pathologists and one otolaryngologist who specialized in voice disorders. Two versions of the questionnaire, preintervention and postintervention versions, were developed. The preintervention version was used to obtain demographic data on the participants and investigate the participants’ vocal habits, habitual voice use behavior, and awareness of their vocal symptoms. The postintervention questionnaire focused on evaluating the participants’ awareness of their vocal symptoms. The internal reliability (ie, the consistency among the items and questions) of the questionnaire was high (Cronbach’s α = .922). Aerodynamic analysis Maximal phonation time. The participants inhaled deeply and then phonated an /ah/ sound at the most comfortable pitch and loudness for as long as possible. Each participant repeated this task three times, and the longest /ah/ sound was used as the MPT of the participant.

S/Z ratio. Using the procedure applied in measuring the MPT, the participants produced /s/ and /z/ sounds for as long as possible. The task was repeated three times, and the longest /s/ and /z/ sounds were used to calculate the s/z ratio. S/Z ratio allows for the interpretation of vocal adduction efficiency and laryngeal control ability.

FIGURE 2. To ensure that only oral expiration was performed, a nose clip was used during expiratory muscle training.

week of training by using the method described by Ruddy et al.13 Outcome measures The outcome of this study was measured using (1) expiratory muscle pressure measurement, (2) a self-administered questionnaire designed to measure people’s awareness of their voice symptoms and voice use behaviors, (3) an aerodynamic analysis of vocal performance, and (4) a pulmonary function test. Expiratory muscle pressure measurement Expiratory muscle pressure was measured using a digital mouth pressure meter (Micro RPM; Micro Medical, UK) and using American Thoracic Society/ERS (European Respiratory Society).14 The MEP was used as the index of expiratory muscle function. The test was repeated 10 times for each participant, and the three highest MEP values for which the variability was less than 5% were averaged and recorded as the MEP.

Pulmonary function testing Pulmonary function was tested using the spirometer (Spirolab III, MIR Co., Italy) and three parameters, forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC%, were measured using guidelines of American Thoracic Society/European Respiratory Society.14 To ensure that evaluation was precise, all tests were repeated three times, and only data for which the variability was less than 5% and only data that represented more than 6 seconds of expiration time were recorded.

Statistical analysis The categorical variables are presented as percentages and the continuous variables are presented as the mean, standard deviation, and median values. The Mann-Whitney U test and Pearson chi-square test were applied to the demographic data and to the analysis of the differences in outcome between the study group and the control group. SPSS software statistical package (SPSS Inc., Chicago, IL, version. 19.0) was employed in all statistical analyses, and P values less than 0.05 indicated statistical significance.

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TABLE 2. MEP, the Longest Time of /S/ and /Z/, and Variability Percentage After Intervention Between and Within the Study Group and the Control Group Study (n = 15) Before

After

Variable

Mean

Mean

△%

The longest time of /S/ The longest time of /Z/ MEP

20.73 18.52 54.61

24.51 20.55 113.98

24.35 17.84 131

Control (n = 14) Before

After

P†

Mean

Mean

△%

P†

P‡

0.017* 0.078 0.001*

22.71 19.00 67.73

21.99 18.38 78.59

−0.74 −4.98 24

0.638 0.363 0.109

0.018* 0.026* 0.000*

Notes: Within group: Wilcoxon signed rank test. Between group: Mann-Whitney U test. * P < 0.05. † The P value within the study group and the control group respectively before and after EMST. ‡ The P value between the study group and the control group before and after EMST. Abbreviations: MEP, maximal expiratory pressure; △%, the percentage of the change before and after EMST.

RESULTS MEP The MEP increased significantly in the study group post intervention (Table 2). Aerodynamics results Both the study group and the control group exhibited no significant differences in the MPT and S/Z ratio. However, the study group exhibited significant improvements in the durations of /s/ and /z/ sounds post intervention s(z) duration postEMST − s (z) duration preEMST ( ×100%) (S: s(z) duration preEMST P = 0.018; Z: P = 0.026), whereas the control group exhibited no significant improvements. Further analysis revealed that the participants in the study group whose S/Z ratio is >1 exhibited significant improvement post intervention (from 17.13 ± 7.98 s to 20.11 ± 7.26 s, P = .025). For participants in the study group whose S/Z ratio is >1, the duration of the /s/ sound also lengthened post intervention (from 17.50 ± 7.02 s to 22.21 ± 7.32 s, P = .018). By contrast, no significant improvement was observed in the control group. Among the participants in the study group whose S/Z ratio was greater than 1.2, the duration of the /z/ sound increased significantly after 5 weeks of training (P = 0.043), whereas no significant difference in the duration of the /s/ sound was observed in the control group (P = 0.50) (Table 2). Pulmonary function test No significant improvement of the pulmonary function test parameters, namely FVC, FEV1, FEV1/FVC%, was observed in the study and control groups post intervention (FVC: P = 0.844; FEV1: P = 0.711; FEV1/FVC%: P = 0.407). Self-awareness of vocal symptoms questionnaire The study group exhibited significant improvement in two sections of the postintervention questionnaire: “self-awareness of voice problems” and “self-awareness of vocal health” (P = 0.016). However, no significant difference in the “influence of voice dysfunction” section was observed in the study group or in the control

group (Table 3). Further analysis of the questionnaire data revealed that the study group exhibited significant improvement in the scores for the items “cannot speak for a long time” (preintervention: 3.67 ± 0.72; postintervention: 2.80 ± 0.68, P < 0.001) and “feels difficult to speak” (preintervention: 3.73 ± 1.16; postintervention: 2.60 ± 0.74, P < 0.002), whereas the control group exhibited no significant improvement in any of the sections and items of the questionnaire. DISCUSSION Pulmonary function and voice No improvement was observed in the parameters of the pulmonary function test, namely FVC, FEV1, and FEV1/FVC. The correlation between pulmonary function and the voice has not been investigated thoroughly. Analysis of the vocal control and respiratory behavior of professional singers has revealed that they can use their pulmonary function more flexibly and that they can initiate singing at higher level of vital capacity to use their vocal folds more dynamically. Hence, Lam Tang et al inferred that the stability of the respiratory system can influence vocal patterns.15 A study indicating that EMST can improve the FVC, FEV1, and MEP of spinal cord injury patients supported this inference.16 However, a previous study observed no improvement in the FVC, FEV1, and FEV1/FVC of patients with Parkinson’s disease, and no correlation between the peak expiratory flow and VHI,17 suggesting that EMST might have no effects on voice performance. Based on the aforementioned findings,12 the correlation between the pulmonary function and the vocal performance remains unclear, and further study is required to determine the correlation between other parameters of pulmonary function and the voice. Effects of aerodynamics on the voice The results of our study indicated that the participants exhibited longer MPTs, but the difference between pre- and postintervention scores was nonsignificant. The S/Z ratio did not change, but the difference between the pre- and postintervention durations for which the participants could phonate /S/ and /Z/ sounds was significant.

Study (n = 15)

Control (n = 14)

Preintervention Postintervention

Preintervention Postintervention

Mean ± SD

P

Mean ± SD

Mean ± SD

P

P

Self-awareness of vocal health 1. Throat symptoms when unaffected by a common cold (1) Throat pain (2) Throat muscle tightness (3) Dry throat (4) Clogged throat 2. Vocal symptoms when not affected by a common cold (1) Cannot speak for a long time (2) Speaking is difficult (3) Voice breaks when talking (4) Hoarseness (5) Cannot speak loudly (6) Vocal range narrows Self-awareness of vocal problems 3. Effects on work (1) Reduced talking time because of voice problems (2) Performance is affected by voice disorder (3) Have experienced changes in work because of voice disorder (4) Have asked for leave because of voice disorder 4. Effects on mood (1) My abnormal voice makes me feel depressed (2) My abnormal voice causes my self-confidence to deteriorate (3) My abnormal voice makes me feel stressed 5. Impact on communication (1) I must repeat statements (2) People experience difficulty in hearing what I say in noisy environments 6. Impact on social life (1) My abnormal voice deters me from talking with others (2) My abnormal voice causes me to experience difficulty in participating in meetings and activities (3) My abnormal voice causes me to experience difficulty in contributing to conversations

34.07 ± 4.76 13.2 ± 3.39 2.87 ± 0.99 3.47 ± 1.13 3.8 ± 0.78 3.07 ± 1.39 20.87 ± 3.14 3.67 ± 0.72 3.73 ± 1.16 3.13 ± 1.13 3.53 ± 0.99 3.20 ± 1.01 3.60 ± 1.18 29.20 ± 9.99 8.00 ± 2.24 2.67 ± 0.98 2.40 ± 0.91 1.60 ± 0.91

30.93 ± 4.46 13.13 ± 2.97 2.87 ± 1.19 3.80 ± 0.78 3.87 ± 0.83 2.60 ± 1.30 17.8 ± 2.96 2.80 ± 0.68 2.60 ± 0.74 2.60 ± 1.35 3.07 ± 0.96 3.27 ± 0.70 3.47 ± 0.99 27.67 ± 8.60 8.60 ± 1.72 3.20 ± 0.94 2.67 ± 0.82 1.53 ± 0.64

0.021* 0.937 1.00 0.163 0.705 0.109 0.001* 0.000* 0.002* 0.085 0.124 0.739 0.564 0.460 0.326 0.046* 0.357 0.739

30.43 ± 2.28 11.14 ± 1.96 2.29 ± 0.83 3.21 ± 0.98 3.43 ± 0.76 2.21 ± 0.98 19.29 ± 2.27 4.00 ± 0.79 4.00 ± 0.68 2.43 ± 1.02 2.93 ± 1.07 2.64 ± 0.93 3.29 ± 1.07 24.14 ± 9.02 7.71 ± 5.03 2.29 ± 0.73 1.94 ± 0.93 1.93 ± 2.13

30.14 ± 6.71 11.07 ± 2.20 2.57 ± 0.85 3.14 ± 0.95 3.29 ± 0.61 2.07 ± 0.73 19.07 ± 5.15 3.57 ± 1.28 3.79 ± 0.89 2.79 ± 1.05 2.93 ± 1.41 2.79 ± 1.19 3.21 ± 1.12 22.57 ± 6.33 6.71 ± 1.94 2.36 ± 0.93 1.93 ± 0.83 1.36 ± 0.50

0.861 0.952 0.083 0.271 0.885 0.480 0.659 0.107 0.317 0.201 0.963 0.942 0.763 0.860 0.809 0.655 1.0 0.527

0.793 0.097

1.33 ± 0.62 7.60 ± 3.72 2.67 ± 1.29 2.33 ± 1.54

1.20 ± 0.41 7.13 ± 3.30 2.60 ± 1.24 2.20 ± 1.15

0.414 0.480 0.803 0.623

1.57 ± 2.14 5.29 ± 2.61 2.00 ± 1.18 1.50 ± 0.86

1.07 ± 0.27 4.71 ± 2.59 1.71 ± 0.99 1.57 ± 0.94

0.655 0.391 0.048* 0.234 0.763

2.60 ± 1.24 6.73 ± 2.67 3.40 ± 1.30 3.33 ± 1.45

2.33 ± 1.18 5.93 ± 1.91 2.93 ± 1.03 3.00 ± 1.07

0.357 0.143 0.10 0.273

1.79 ± 0.89 5.57 ± 2.44 2.79 ± 1.19 2.79 ± 1.31

1.43 ± 0.76 5.86 ± 1.56 2.71 ± 1.07 3.14 ± 0.77

0.059 0.470 0.911 0.763 0.285

6.87 ± 3.38 2.73 ± 1.49 2.07 ± 1.03

6.00 ± 2.90 2.20 ± 1.01 1.87 ± 1.06

0.242 0.142 0.366

5.57 ± 2.88 2.21 ± 1.19 1.64 ± 0.93

5.29 ± 1.73 2.07 ± 0.73 1.64 ± 0.63

0.903 0.563 0.564 1.0

2.07 ± 1.10

1.93 ± 0.96

0.527

1.71 ± 0.99

1.57 ± 0.65

0.48

0.569

0.137 0.015*

Notes: Within group: Wilcoxon signed rank test. Between groups: Pearson chi-square test. * P < 0.05.

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Mean ± SD

Expiratory Muscle Strength Training and Voice Disorders

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Yuan-Ching Tsai et al

TABLE 3. Differences in Questionnaire Results Between and Within the Study Group and the Control Group

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Expiratory muscle training increased the durations for which the participants in the study group whose S/Z ratio was >1 (poor control of laryngeal muscles; short duration of expiratory time) could produce the /Z/ sound, as well as the duration for which the participants in the study group whose S/Z ratio was

The Effects of Expiratory Muscle Strength Training on Voice and Associated Factors in Medical Professionals With Voice Disorders.

This research used expiratory muscle strength training to explore the factors relevant to medical professionals with voice disorders. The maximal expi...
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