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Published on January 23, 2008

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Vocal Fatigue: Updated Definitions, Measures, and Treatment Strategies:  Vocal Fatigue: Updated Definitions, Measures, and Treatment Strategies Nancy Pearl Solomon, Ph.D., CCC-SLP Research Speech-Language Pathologist Nancy.P.Solomon@US.ARMY.MIL Army Audiology & Speech Center Walter Reed Army Medical Center The opinions or assertions contained herein are the private views of the Author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. International Perspectives:  International Perspectives Voice disorders viewed as an issue of occupational safety and health Finland (Vilkman, Sala, Rantala, Vintturi, Jónsdottir, …) Australia (Russell, Oates, Mattiske, Greenwood) USA (McCabe, Roy, Smith, Titze, Verdolini, …) Poland Sweden Iceland Belgium Brazil The Netherlands What is Vocal Fatigue?:  What is Vocal Fatigue? “…a frequent descriptor for a well-known set of symptoms…” (Stemple, Glaze, & Klaben, 2000) Common Symptoms of Vocal Fatigue:  Common Symptoms of Vocal Fatigue Increased vocal effort and discomfort Reduced pitch range and flexibility Reduced vocal projection (power) Reduced control of vocal quality Symptoms increase across the speaking day Improvement after resting (Colton & Casper, 1996; Gotaas & Starr, 1993; Stemple, Glaze, & Klaben, 2000) Vocal Fatigue By Any Other Name…:  Vocal Fatigue By Any Other Name… “vocal attrition” … (Sapir, 1993) “a temporary decrement of vocal function with vocal use” (Sivansankar & Fisher, 2003) “… a vocal loading-borne change manifested as physiological, perceptual, or subjective changes.” (Vintturi, 2001) Vocal Loading as a Continuum:  Vocal Loading as a Continuum (Vintturi, 2001; Vilkman, 2004) Vocal loading: prolonged use of voice Vocal warm-up: occurs at the beginning of vocal loading Post-loading short vocal rest: a break in vocal loading Regarded as phases on a continuum Phonatory Effort Increases With Vocal Fatigue:  Phonatory Effort Increases With Vocal Fatigue “… a progressive increase in phonatory effort accompanied by a progressive decrease in phonatory capabilities.” (McCabe & Titze, 2002) Fatigue is … “… a progressive increase in the effort required to exert a desired force and the eventual progressive inability to maintain this force in sustained or repeated contractions.” (Enoka & Stuart, 1985) Definition of “Pure” Vocal Fatigue:  Definition of “Pure” Vocal Fatigue The client reports a change in the way the voice feels or sounds during or after prolonged vocal use Symptoms include vocal tiredness, effort, discomfort, reduced function Acoustic, perceptual, and anatomical changes are subtle and nonspecific Improvement with vocal rest Absence of vocal lesions Absence of dysphonia Fatigue Mechanisms:  Fatigue Mechanisms Central Peripheral Potential Mechanisms of Vocal Fatigue:  Potential Mechanisms of Vocal Fatigue Central (mental) fatigue Report of tiredness Sense of effort Peripheral (muscle) fatigue Laryngeal Respiratory Biomechanical properties of tissue Stress and strain Viscosity Vocal Effort:  Vocal Effort A common complaint in vocal fatigue Respiratory effort Increases with expiratory and inspiratory loading (Gandevia, Killian, & Campbell, 1981; Supinski, Clary, Bark, & Kelsen, 1987; Suzuki, Suzuki, Ishii, Akahori, & Okubo, 1992) Phonatory effort Increases with vocal loading (Stemple, Stanley, & Lee, 1995; Solomon & DiMattia, 2000; Chang & Karnell, 2001; Vilkman, 2004) Intrinsic Laryngeal Muscles:  Intrinsic Laryngeal Muscles Largely fatigue resistant Human intrinsic laryngeal muscle fiber types Type I (nonfatiguable) 54% Type IIa (fatigue resistant) 37% Type IIb (fatiguable) 6% (Claassen & Werner, 1992) Muscle stimulation in anesthetized dogs Thyroarytenoid muscle was nonfatiguable after 1 hour (Cooper & Rice, 1990) Respiratory Muscle Fatigue:  Respiratory Muscle Fatigue Unless performing whole body exercise at very high intensity levels, the respiratory muscles are unlikely to fatigue (Dempsey & Babcock, 1995; McKenzie & Bellemare, 1995) Nonmuscular Tissue Fatigue:  Nonmuscular Tissue Fatigue Vocal fold cover = epithelium, and superficial and intermediate layers of lamina propria Stress relaxation can lead to increased vocal fold strain (lengthening) and compensatory adjustments to increase tension (based on Hirano, 1974) Tissue Viscosity & Hydration:  Tissue Viscosity & Hydration The fluids in and around the vocal folds act as a mechanical lubricator and shock absorber Internal (systemic) and external (superficial) hydration can affect vocal fold viscosity Prolonged, high-pitched phonation leads to increased frictional energy loss, increased heat dissipation, and increased tissue viscosity (Cooper & Titze, 1985; Hammond, Zhou, Hammond, Pawlak, & Gray, 1997; Titze, 1994) Conceptual Model of Vocal Fatigue:  Conceptual Model of Vocal Fatigue (McCabe & Titze, 2002) Vocoergonomics:  Vocoergonomics Premise View occupational voice problems as an occupational safety and health (OSH) issue Training to improve vocal technique often is not economically or practically feasible Vocoergonomic (Loading) Factors Air quality (humidity, cleanliness) Noise (output level, background, reverberation) Posture (sitting, standing) (Vilkman, 2004) Who Is At Risk For Voice Disorders?:  Who Is At Risk For Voice Disorders? Teachers (Roy et al., 2004; Russell et al., 1998; Sala et al., 2001, 2003; Smith et al., 1998; Vilkman, 2004) Telemarketers (Jones et al., 2002) Drill sergeants (Mann et al., 1999) Auctioneers (McHenry & Carlson, 2004) (Fritzell, 1996; Titze, Lemke, & Montequin, 1997) Teaching Requires How Much Phonation??!:  Teaching Requires How Much Phonation??! Phonation occurs 15-40% of the time during a teaching day Vocal folds vibrate ~1,000,000 times per teaching day for women teachers, and about half as much for men Obvious potential for phonotrauma (Vilkman, 2004) Laboratory versus Field Research:  Laboratory versus Field Research Laboratory studies Controlled vocal-loading tasks Non-portable equipment e.g., videostroboscopy, aerodynamics Sound-treated, controlled environment Field studies Performance, work day, … Portable equipment e.g., voice accumulators, rating scales Ecologically valid Experimentally Induced Vocal Fatigue:  Experimentally Induced Vocal Fatigue Vocal change occurs after 1-2 hours Based on vibrational exposure to tissue, safe vocal performance time for reading is estimated to be ~ 35 minutes (Titze, Švec, & Popolo, 2003) Inconsistent changes in acoustic parameters and laryngeal features changes in speaking pitch acoustic instabilities unusual glottal configuration laryngeal edema Selecting Measures for Vocal Fatigue Studies:  Selecting Measures for Vocal Fatigue Studies Acoustic and auditory-perceptual Inconsistent findings from previous literature Too much variability to be informative Visual perceptual Suggestions of unusual glottal configurations Should reveal muscular and nonmuscular changes Selecting Measures for Vocal Fatigue Studies:  Selecting Measures for Vocal Fatigue Studies Effort perception Affected by vocal loading Should reflect central fatigue Aerodynamics Depend on respiratory-laryngeal interaction Should reflect biomechanical properties of nonmuscular laryngeal tissue Phonation Threshold Pressure (PTP, Pth ):  Phonation Threshold Pressure (PTP, Pth ) The minimum lung pressure required to initiate vocal fold oscillation Determined by static, vibratory, and viscous properties of the vocal folds Measured orally (noninvasive) May correspond with “ease of phonation” (Titze, 1988, 1992) An “unhappy triad”:  An “unhappy triad” Vilkman (2004) proposed that Elevated phonation threshold Heightened vocal fundamental frequency Increased effort Represent the greatest risk to vocal health Vocal Loading & Vocoergonomics:  Vocal Loading & Vocoergonomics 80 young adults Three 45-min reading sessions 45-min lunch break Two 45-min reading sessions Conditions (n = 5 each) Male or female High or low output High or low humidity Sitting or standing (Vintturi et al., 2003; Vilkman, 2004) Vocal Loading & Vocoergonomics:  Vocal Loading & Vocoergonomics Questionnaire (17 items; score 0-10) Factor 1: central fatigue I love it …………………… I don’t like it anymore I am doing well ……… I am tired Factor 2: symptoms of the neck, shoulders, and back Factor 3: drying in the mouth and throat Factor 4: symptoms of the throat Factor 5: symptoms of the voice Increase in all factors before lunch Slight reduction in all factors after lunch EXCEPT central fatigue (Vintturi et al., 2003; Vilkman, 2004) Slide28:  Factor 1: central fatigue Factor 2: symptoms of the neck, shoulders, and back Factor 3: drying in the mouth and throat Factor 4: symptoms of the throat Factor 5: symptoms of the voice (Vintturi et al., 2003) Vocal Loading and Voice Measures:  Vocal Loading and Voice Measures Changes from morning to afternoon Increased SPL Increased intraoral (subglottal?) pressure Increased amplitude of flow Increased peak amplitude of differentiated flow Indicates increased effort and phonatory threshold. Effects reduced after lunch break (Vilkman, Lauri, Alku, Sala, & Sihvo, 1999; Vilkman, 2004) How Can the Voice Be Prepared for Vocal Loading?:  How Can the Voice Be Prepared for Vocal Loading? Will drinking water help? Is a more humid environment beneficial? What about vocal warm-up exercises? Do breaks help? How long? How often? Hydration Studies: PTP increases with dehydration:  Hydration Studies: PTP increases with dehydration systemic and superficial combined (Verdolini-Marston et al., 1990; Verdolini et al., 1994) systemic alone (Finkelhor et al., 1988; Verdolini et al., 2002; Fisher et al., 2001) superficial alone (Verdolini et al., 1996; Jiang et al., 1999; Roy et al., 2003; Sivasankar & Fisher, 2002, 2003) Vocal Loading and Systemic Hydration:  Vocal Loading and Systemic Hydration Do PTP and self-perceived phonatory effort (PPE) increase after a prolonged loud-reading task? Do these changes vary with drinking water? Do these changes differ between women and men? (Solomon & DiMattia, 2000; Solomon, Glaze, Arnold, & van Mersbergen, 2003) Method:  Method 4 women and 4 men with normal voices Hydration conditions: low, high, typical Read loudly for 2 hours Measures PTP Self-perceived phonatory effort (PPE) Laryngeal imaging (Solomon & DiMattia, 2000; Solomon, Glaze, Arnold, & Van Mersbergen, 2003) Results:  Results PTP increased for all 8 participants PTP tended to increase more or earlier in the low-hydration condition for women 80% of pitch range (Solomon & DiMattia, 2000; Solomon et al., 2003) Results:  Results An anterior gap or spindle-shaped glottis was observed after loud reading for half of the samples No differences between sexes or hydration conditions for vibratory closure pattern (Solomon & DiMattia, 2000; Solomon et al., 2003) Vocal Loading and Superficial Hydration:  Vocal Loading and Superficial Hydration Five 45-min sessions of oral reading 40 young adults in each of two conditions Different seasons in Helsinki, Finland High humidity: Sept-Dec 65% +5% Allowed to drink water Low humidity: January 25% +5% No water to drink before lunch (after 3 loading sessions) Aided by a vaporizing humidifier (Vinturri et al., 2003) Effects of Ambient Humidity:  Effects of Ambient Humidity Results pooled over the entire test day More severe symptoms for low-humidity group Greater differences seen when examining loading sessions separately, especially for women (Vinturri et al., 2003) Low High Vocal Loading, Systemic Hydration, and Vocal Rest:  Vocal Loading, Systemic Hydration, and Vocal Rest Method 20 karaoke singers Water and rest periods (n = 10) No water, no rest periods (n=10) Continuous karaoke singing Results Group with water and rest periods sang longer Group without water or rest Jitter increased Highest pitch decreased (Yiu & Chan, 2003) Vocal Warm-Up Activity:  Vocal Warm-Up Activity 10 minutes of oral reading No differences (Solomon & DiMattia, 2000) 45 minutes of oral reading (high and low output) Many differences, depending on gender and type of phonation Differences attributed to warm-up effect (Vilkman, 2004; Vintturi, 2003) Vocal Warm-Up Exercises:  Vocal Warm-Up Exercises Recommended to reduce the occurrence or severity of vocal fatigue (Blaylock, 1999; Elliot, Sundberg, & Gramming, 1995) Based on principles of fatigue prevention from the sports medicine literature Warm-Up Exercises:  Warm-Up Exercises Presumed to (Safran, Seaber, & Garrett, 1989) Increase blood circulation Increase respiration Warm up muscles Decrease muscle viscosity Improve muscle contraction Increase muscle elasticity Effects are apparent after brief exercise Improved general muscle function after 20-30 minutes (Kulund & Töttössy, 1983) Vocal Warm-Up Exercises:  Vocal Warm-Up Exercises Elliot, Sundberg, & Gramming (1995) 10 amateur singers 30 min vocal warm-up exercises Voices felt better Inconsistent changes in PTP Motel, Fisher, & Leydon (2003) 10 trained sopranos 10 minutes vocal warm-up exercises PTP increased at high pitch No significant change in pitch range Vocal Warm-Up Exercises and Vocal Fatigue:  Vocal Warm-Up Exercises and Vocal Fatigue 8 women with vocal fatigue 15-20 minutes of vocal preparation warm-up exercises vocal rest and relaxation 1 hour of loud oral reading Measures Phonational threshold pressure Phonatory effort (Milbrath & Solomon, 2003) Vocal Warm-Up Exercises (Milbrath & Solomon, 2003):  Vocal Warm-Up Exercises (Milbrath & Solomon, 2003) Respiration Stretching Breathing Resonance Humming Phonation Vocal Function Exercises (Stemple et al., 2000) Results PTP:  Results PTP Mean data (N=8) Results:  Results Warming up the voice did not benefit vocal function, as assessed by PTP and PPE Negative results could relate to habitual phonation styles in persons with chronic vocal fatigue One brief warm-up session was probably inadequate One hour of loud phonation was probably inadequate Now what??:  Now what?? What if vocal warm-up exercises are trained and performed for weeks? Conditioning Exercise:  Conditioning Exercise Purpose: To increase Strength Flexibility Endurance Methods include Stretching Resistance training Aerobic conditioning Vocal Function Exercises (VFE):  Vocal Function Exercises (VFE) Developed by Stemple and colleagues (1994) Intended to improve strength, endurance, and coordination Strives to balance the subsystems of voice production (respiratory, phonatory, resonatory) Recommended schedule: twice daily 6-8 weeks systematic taper Effectiveness of Vocal Function Exercises for Normal Voices:  Effectiveness of Vocal Function Exercises for Normal Voices 35 women with no voice disorders 4 weeks Vocal function exercises Placebo exercises No exercises Improved maximum phonation duration and pitch range after vocal function exercises (Stemple, Lee, D’Amico, & Pickup, 1994) Similar improvements in 10 singers (Sabol, Lee, & Stemple, 1995) Effectiveness of Vocal Function Exercises:  Effectiveness of Vocal Function Exercises 58 teachers with voice disorders 6 weeks, with appointments every 2 weeks Vocal function exercises, n = 19 Vocal hygiene, n = 20 No treatment, n = 19 After vocal function exercises Reduced score on the Voice Handicap Index Reported overall voice improvement Greater ease and clarity for speaking and singing (Roy, Gray, Ebert, Dove, Corbin-Lewis, & Stemple, 2001) Chant Therapy for Teachers with Vocal Fatigue:  Chant Therapy for Teachers with Vocal Fatigue 4 teachers with > 4 years of vocal fatigue 6 1-hr sessions over 2 weeks Chant therapy Physiologic recovery treatment (placebo) (McCabe & Titze, 2002) Chant Therapy:  Chant Therapy A type of singing exercise Gregorian chant pattern Selected higher than typical pitch (McCabe & Titze, 2002) Chant Therapy for Teachers with Vocal Fatigue:  Chant Therapy for Teachers with Vocal Fatigue Vocal-loading task 2 hours of loud reading Chant therapy: Response to vocal loading Smaller changes in vocal effort and quality Faster recovery (McCabe & Titze, 2002) Resonant Voice Therapy (RVT):  Resonant Voice Therapy (RVT) Developed by Verdolini (2000), based on Lessac (1997) Intended to achieve a strong, clear voice with little effort Strives to achieve vibratory sensations in the facial bones and minimal vocal fold impact Recommended schedule weekly therapy twice daily home practice 8 weeks Effectiveness of Resonant Voice Therapy:  Effectiveness of Resonant Voice Therapy 13 women with vocal nodules 9 sessions in 2 weeks Resonant voice therapy + Vocal Hygiene Confidential voice therapy + Vocal Hygiene Vocal Hygiene Both resonant voice therapy and confidential voice therapy were successful IF used!! (Verdolini-Marston, Burke, Lessac, Glaze, & Caldwell, 1995) Effectiveness of Resonant Voice Therapy:  Effectiveness of Resonant Voice Therapy 64 teachers with voice disorders 6 weeks Resonant voice therapy, n = 19 Voice amplification, n = 25 Respiratory muscle training, n = 20 Resonant voice therapy and Voice amplification Reduced scores on Voice Handicap Index Reduced self-ratings of severity Voice amplification Improved overall voice, vocal clarity, ease (Roy, Weinrich, Gray, Tanner, Stemple, & Sapienza, 2003) Using Amplification:  Using Amplification 44 teachers with voice difficulties Groups Voice amplification, n = 15 Vocal hygiene, n = 15 No treatment, n = 14 Measures Voice Handicap Index Voice Severity self-rating scale Acoustic measures (Roy, Weinrich, Gray, Tanner, Toledo, et al., 2002) Using Amplification:  Using Amplification Amplification group: significantly reduced VHI, self-rated severity, jitter, and shimmer greater vocal clarity, ease, and compliance (Roy, Weinrich, Gray, Tanner, Toledo, et al., 2002*) [*see related Letter to the Editor by Dworkin et al., and response by Roy et al. in JSLHR, 47, 353-365] Using Amplification:  Using Amplification 5 teachers with voice difficulties Protocol Recorded at the beginning and end of one day Cordless sound amplification for > 1 week Recorded with amplification Measures F0 SPL F0 and SPL increased both days Greater increases with amplification Greater ease and less fatigue with amplification (Jónsdottir, Laukkanen, & Vilkman, 2002) Using Amplification:  Using Amplification Amplification promotes greater vocal ease and comfort Suggest that increased F0 and SPL are adaptive to vocal loading and may “promote effective voice production” (Jónsdottir et al., 2002, 2003) Prevention and Training:  Prevention and Training 2-day Vocal Training course Lectures about voice, resonance, & articulation Vocal exercises 1-day Speech Communication seminar 38 women, 10 men Call-center customer service advisors Environment: quiet, dry (19% humidity) No chronic voice problems; some mild symptoms (Lehto, Rantala, Vilkman, Alku, & Bäckström, 2003) Prevention and Training (Lehto et al., 2003):  Prevention and Training (Lehto et al., 2003) Questionnaires 11 symptoms (e.g., fatigue, hoarse, dry, …) 1 item re: change with training 23 statements about the training course Before training Most common symptom: need to clear mucus Other: dry throat, voice fatigue, hoarseness After training 50% reported reduction in need to clear throat 60% reported improvement in vocal habits 60% of women reported less vocal fatigue Prevention and Training:  Prevention and Training 55 teachers-in-training, no voice problems Groups Control, n = 23 Indirect training (1 lecture), n = 20 Direct training (1 lecture + 1 technique), n = 12 Measures Dysphonia Severity Index (Wuyts et al., 2000) Vocology Screening Profile (Hazlett, 2001) Voice Handicap Index (Jacobson et al., 1997) No significant differences (Duffy & Hazlett, 2004) Take-home messages:  Take-home messages Vocal fatigue ... Is self-perceived and may not be heard Occurs over time with vocal use Involves an increased sense of vocal effort Is viewed as an issue of occupational safety and health Is affected by environmental factors Take-home messages:  Take-home messages Vocal fatigue benefits from … Not vocal hygiene or respiratory training alone Not one brief session of vocal warm-up exercises Maybe drinking water for some people Maybe a humid environment Probably amplification Probably providing periods of vocal rest Probably a vocal conditioning/training program 2-8 weeks References:  References Blaylock, T.R. (1999). Effects of systematized vocal warm-up on voices with disorders of various etiologies. Journal of Voice, 13, 43-50. Chang, A., & Karnell, M. (2001, June). The relationship among vocal fatigue, perceived phonatory effort and phonation threshold pressure (PTP). Talk presented at The Voice Foundation’s 30th Annual Symposium: Care of the Professional Voice, Philadelphia. 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