Objective measures of voice production in patients complaining of laryngeal fatigue

Journal of Voice Vol. 10, No. 2, pp. 146-154 © 1996 Lippincon-Raven Publishers. Philadelphia

Objective Measures of Voice Production in Patients Complaining of Laryngeal Fatigue Carol S. Eustace, t Joseph C. Stemple, and *Linda Lee Department of Speech Pathology and Audiology, Tile Christ Hospital: *University of Cincinnati, Cincinnati; and ilnstitute for Voice Analysis and Rehabilitation, Dayton, Ohio, U.S.A.

Summary: The purpose of this retrospective study is to describe results of acoustic, aerodynamic, and videostroboscopic measures in patients complaining of laryngeal fatigue. Data were collected from 88 patients whose primary complaint was chronic laryngeal fatigue in the absence of visible laryngeal pathologies. The results revealed an abnormally high airflow rate and decreased maximum phonation time. An anterior glottal chink, anterior and posterior glottal chinks, or spindle-shaped glottal closure were found in 61% of the subjects. Key Words: Laryngeal fatigue analysis--Acoustic measures-Aerodynamic measures--Videostroboscopy measures--Glottal chink.

This in turn causes a slight "bowing" of the vocal folds, allowing an escape of air from the glottis, thus causing a breathy voice. Hirano et al. (4) and Jackson (5) also suggested involvement of the thyroarytenoid muscle in voice fatigue. Laryngeal fatigue is commonly seen in professional voice users such as singers, actors, members of the clergy, and lecturers (2,6). Stemple (7) speculated that almost all voice disorders will demonstrate laryngeal muscle weakness. He reported a case study of an opera singer who pushed her voice "to its upper limit" so often during practice that her laryngeal muscles were fatigued. Stemple (8) further discussed that the result of fatigue will often be a lack of complete closure of the vocal folds. With incomplete closure of the folds, there will be increased air pressure and airflow as the patient attempts to maintain phonation. Therefore, the patient is creating more fatigue as the effort to produce voice is increased. Koufman and Bialock (9) examined a group of vocal misuse and vocal abuse syndromes in professional voice users. They found that the majority of these professional voice users presented with a laryngeal MTD. Instead of classifying these disorders by the classical terms of laryngeal myasthenia or hyperkinetic dysphonia, they chose the term laryn-

Laryngeal fatigue is a common functional voice complaint usually appearing along with a combination of other symptoms. Patients with laryngeal fatigue might describe their symptoms as feeling vocally tired after a prolonged period of talking accompanied by the sense that much effort is required to continue speaking. They may feel tightness in the throat and chest or experience varying degrees of dysphonia with the condition progressively becoming worse by the end of the day. It may be difficult for the patient to talk loudly, or they may find themselves talking in a monopitch (i). Koufman and Isaacson (2) reported that vocal fatigue symptoms are sometimes seen in patients with lesions, or in patients with functional disorders without lesions, and are "almost always associated with abnormal laryngeal muscle tension" (p. 986). These authors described these symptoms with the term muscle tension dysphonia (MTD). Using the classical term of myasthenia laryngis, Greene (3) described vocal fatigue as a weakness in the thyroarytenoid muscle due to vocal abuse or straining.

Address correspondence and reprint requests to Carol S. Eustace at Department of Speech Pathology and Audiology, The Christ Hospital, 2139 Auburn Avenue, Cincinnati, OH 45219, U.S.A.

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LAR YNGEAL FATIGUE geal tension-fatigue syndrome (TFS). They asserted that this syndrome is a functional voice disorder because it presents with abnormally low voice pitch and poor breath stream control resulting in a breathy voice, vocal fatigue, and intermittent dysphonia. Their contention was that laryngeal fatigue is caused by muscular tension in these professional voice users. Prater (10) further contended that TFS is also commonly seen in nonprofessional voice users. Abnormal habitual pitch is considered to be a factor in laryngeal fatigue. The literature gives evidence of both inappropriately high- and low-pitched voice levels as a cause of laryngeal muscle tension leading to fatigue. Sander and Ripich (I 1) asserted that laryngeal muscles will strain the easiest at the lowest pitched voice. On the other hand, these authors cited a relationship between increased laryngeal muscle activity (increased tension) with the rising of vocal pitch. Stone and Shaft (12) demonstrated that use of higher pitched phonations produced voice fatigue earlier than did lower pitched voices. Colton and Casper (1) reported that using the lowest end of the pitch range (glottal fry) will cause increased muscle tension, as does using an inappropriately high-pitched voice. Koufman and Blalock (9) also reported a relationship between using low pitch levels and laryngeal fatigue or ten*,ion-fatigue syndrome. EXPERIMENTALLY INDUCED LARYNGEAL FATIGUE A limited number of studies have examined experimentally induced laryngeal fatigue. Gelfer et al. (13) measured intensity, fundamental frequency, jitter ratio, shimmer, and signal-to-noise ratio (SNR) on two groups of subjects before and after reading for a period of I h at 80% intensity level. One group consisted of 26 trained female singers and the other a group of 24 women untrained in singing. The effects were examined on both the speaking and singing voices. The findings showed a significant difference between pre- and posttest measures for the group of trained singers only in the acoustic measure of jitter ratio for sustaining the vowel/i/. The untrained subjects, however, showed a significant increase in fundamental frequency (F0) and intensity for two out of three vowels, and a significantly worsened SNR f o r / i / and /u/. There was a trend (though not significant) toward an increase in jitter ratio for this latter group for all vowels.

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In a perceptual study, Sherman and Jensen (14) attempted to demonstrate an increase in harshness of voice quality over a period of prolonged phonation (1.5 h). Contradictory to their predictions, the trend was for the normal readers to have a decrease in harshness during the prolonged reading session with an increase back toward the original degree of harshness following a 30-min period of vocal rest. This finding was attributed to the possibility that laryngeal muscular adjustments were made, thus avoiding a level of vocal abuse that would produce physiological changes in the larynx. Scherer et al. (15) examined the effects of a period of prolonged loud phonation on one trained and one untrained voice user. Fiberoptic, acoustic, and subjective factors were rated throughout alternating periods of fatiguing tasks, diagnostic tasks, and vocal rest periods. Their findings showed no significant differences in perturbation values for the untrained subject over time. For the trained voice user, there was a significant increase seen in perturbation over time. After the rest period, however, there was no significant difference between shimmer values, whereas the jitter values remained increased. This finding gives support to the theory that the laryngeal mechanism may adapt after a short period of "warm-up" time. Because the shimmer values decreased and the jitter values remained high, the researchers hypothesized that there is recovery to the part of the vocal system responsible for amplitude variation, whereas there is no recovery to the part of the system responsible for the period perturbation: or, that the system responsible for period variation does not recover as rapidly. Stemple et al. (16) tested 10 women between the ages of 22 to 45 before and after a prolonged reading task. By setting certain prerequisites for the subjects, any significant results could be attributed solely to laryngeal fatigue presenting in an otherwise normal laryngeal system. The prerequisites were that the subjects not be smokers, not live with a smoker, and have no history of vocal abuse. There also was to be no history of previous or existing laryngeal pathologies. For 2 days prior to testing, there was to be no ingestion of any substances that would cause drying of the vocal folds (caffeine and alcohol), and no aspirin to eliminate the chance of hemorrhage. The subjects were also instructed not to be involved in vocally abusive behaviors (singing, loud talking, etc.) on the same day as the test. Each subject performed a reading task that conJournal of Voice, Vol. IO, No. 2, 1996

148

C. S. E U S T A C E E T A L .

sisted of reading for a 2-h period at 75-80 dB sound pressure level, with a 5-min break after the first hour. An objective voice evaluation was performed prior to and immediately following the reading task analyzing acoustic, aerodynamic, and videostroboscopic measures. The acoustic and aerodynamic analyses showed that after prolonged voice use, subjects presented with significant results between pretest and posttest measures and observations. The most important findings were a significant increase in Fo during reading, videostroboscopic evidence of anterior chinks in six of the 10 subjects in posttesting that were not evident during pretesting, and decreased jitter during sustained production of high-pitched vowels. Stemple et al. (16) hypothesized that the increase in F0 could give support to Greene's (3), Hirano et al.'s (4), and Jackson's (5) speculations that thyroarytenoid (TA) muscle weakness is a factor in laryngeal fatigue. Stemple et al. (16) cited Hirano (17) in explaining that when the TA muscle is normally activated, the muscular layer is stiffened "while the cover and transition layers are passively slackened, permitting vibration at a lower frequency" (p. 14). Therefore, with TA muscle weakness, low pitch is difficult to attain. The videostroboscopic evidence of an anterior glottal chink observed in six of the 10 subjects after the extended voice task led the authors to hypothesize that since there were no other physical changes present, the chinks were caused by laryngeal musculature strain from the prolonged reading task. PURPOSE OF THE PRESENT INVESTIGATION As the literature demonstrates, several reports have been published that examine laryngeal fatigue T A B L E 1. T w e l v e m o s t c o m m o n o c c u p a t i o n s , listed in

descending order Occupation

n

Retired Teacher Student (music/theater) Homemaker Student Financial profession Singer Secretary Nurse Minister Computer analyst Mechanic

18 12 10 7 5 5 3 2 2 2 2 2

Journal of Voice, Vol. 10, No. 2, 1996

TABLE 2. Means +-- SDs for fundamental frequency measured in hertz Sex

n

Male Female

25 41

Comfort

High

Low

121.78 - 17.69 200.82 ± 34.41

301.83 - 61.51 514.58 +-- 117.45

103.53± 17.85 161.90± 23.31

Data obtained at comfortable, high and low pitch levels.

and the effects of prolonged voice use. Most research discusses laryngeal fatigue as a secondary symptom due to some type of voice misuse, voice abuse, voice overuse, vocal strain, functional disorders, or pathologies with lesions. There is, however, very little information in the literature regarding the direct measures of voice production in patients who complain of laryngeal fatigue. The present study was retrospective, examining acoustic, aerodynamic, and videostroboscopic data taken from patients who complained of voice fatigue in the absence of other laryngeal pathologies. The purpose of this study was to describe this data, compare it with normative data, and determine which measures and signs of voice production were present. METHODS Subjects Subject data were gathered from patient files obtained at The Professional Voice Center of Greater Cincinnati. The patient files included all subjects seen in the clinic with a primary complaint of chronic laryngeal fatigue in the absence of other pathologies during the years of 1989-1993. Eightyeight subjects, 36 men ranging in age from 19 to 80 years (mean age = 51), and 52 women ranging in TABLE 3. Means +- SDs for fundamental frequency measured in hertz at comfortable pitch compared by age in decades Age range (yr)

Male n

10-19 20-29 30-39 40--49 50-59 60-69 70-79

0 3 3 5 3 9 2

Female

Mean ± SD 117.40 119.07 118.72 104.30 127.99 138.40

--. ± ± --. ± ±

14.91 13.23 11.60 15.63 21.32 10.47

n 4 8 9 II 4 2 3

Mean ± SD 238.75 226.35 191.33 188.62 190.23 "!69.65 190.22

--. 24.38 ± 37.14 ± 17.77 +-- 36.89 ± 24.54 ± 9.83 --. 24.54

Values considered outside the normal range are indicated by an asterisk.

L A R YNGEAL F A TIG U E

T A B L E 4.

Means ± SDs for frequency perturbation (% of fundamental frequency)

Sex

n

Comfort

High

Low

Male Female

25 41

.51 ± .40 .40 ± .18

.25 ± .16 .27 ± .23

.73 ± .57 .54 ± .39

T A B L E 6. Means +-- SDs for reading fundamental frequency measured in hertz at comfortable pitch level

Data obtained at comfortable, high and low pitch levels.

age from 15 to 74 years (mean age = 42), were included in the data analysis. Of the 88 subjects, three men were known smokers, 12 subjects had smoking unreported, and 73 subjects were nonsmokers. Twenty-eight different occupations were reported in the total sample. The 12 most frequently occurring occupations are listed in descending order of frequency in Table I.

Data collection Data collected from the reports of the subjects included both objective and subjective measures. The acoustic and aerodynamic measures of F0, jitter, airflow volume, airflow rate, and maximum phonation time were recorded for the vowels/a/,/i/, and/u/, each at high-, low-, and comfortable-pitch levels. The low- and high-pitch levels of the frequency range were recorded. A reading Fo was also computed. Acoustic and aerodynamic measures were obtained with use of a Visi-Pitch (KayElemetrics Model 6097) and Nagashima Phonatory Function Analyzer (Model PF77H), respectively. Laryngeal stroboscopic evaluation was also conducted for each subject with use of a Rigid Scope (R. Wolf 4450.47) inserted in the back of the subject's oropharynx, stroboscopic lighting (Bruel NKJAER4914), and a Wolf Saticon Tube Camera. A videotape recording was made of laryngeal movements with use of a Panasonic Recorder (AG-6300) and Color Monitor (BT-S-1900N). All data collecMeans ± SDs for frequency perturbation (% of fitndamental frequency), at comfortable pitch compared by age in decades

T A B L E 5.

Age range (yr)

n

Mean ± SD

n

10-19 20-29 30-39 40-49 50-59 60-69 70-79

0 3 3 5 3 9 2

-.33 .35 .53 .36 .52 *1.12

4 8 9 11 4 2 3

Male

Female

-- .21 ± .09 ± .26 --- .34 ± .48 ± .60

Mean - SD .46 .40 .42 .33 .35 .46 .48

--..13 --- .14 - .25 ± .15 --- . 16 ± .09 ± .34

Values considered outside the normal range are indicated by an asterisk.

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Sex

n

Reading fundamental frequency

Male Female

25 41

118.36 - 20.36 190.44 ± 29.71

Values considered outside the normal range are indicated by an asterisk.

tion procedures were consistent with those described in Stemple et al. (16). The videostroboscopy tapes from each subject were examined and a record of subjective observations was made. These included nine dimensions of phonatory function rated on an equal-appearing interval scale. For eight of the dimensions, the equalappearing interval scale had a range of 0 through 5, with 0 being normal and 5 being a severe deviation from the norm. The scale was used for supraglottic activity, vertical level approximation, the condition of the vocal fold edges, amplitude of the vocal fold movement, mucosal wave, percentage of the nonvibrating portion, phase symmetry, phase closure, and glottal closure. The ninth dimension, phase closure, was measured on an ll-point scale ranging from - 5 to 5, with - 5 meaning the open phase predominates, 5 meaning closed phase predominates, and 0 being normal. Finally, glottal closure was given a descriptive rating. The types of closure patterns possible were complete, posterior, irrregular, spindle, anterior, hourglass, and incomplete. The videotapes were reviewed, and the ratings made by a speech pathologist with over 15 years of experience in dealing with voice disorders including an expertise in videostroboscopy.

Data analysis Data means and SDs were computed with use of the Macintosh Microsoft Excel statistical package. The data were divided by sex and age ranges. The results were compared with normative data to observe any differences in the measures. The normative data used for this study were taken from Colton T A B L E 7.

Means ± SDs for frequency range measured in hertz

Sex

n

Lowest pitch

Highest pitch

Male Female

25 41

84.27 ± 15.77 131.30 ± 23.36

527.84 -+ 142.79 895.56 --. 268.58

Data obtained at low- and high-pitch levels.

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T A B L E 8. Means + SDs for frequency range measured in hertz at low- and high-pitch levels compared by age

in decades Male

Age range (yr)

n

L o w frequency

10-19 20-29 30-39 40-49 50--59 60--69 70-79

0 3 3 5 3 9 2

. 76.43 72.97 85.84 67.63 91.78 100.20

----± ± ± ±

. . 13.49 9.02 12.16 2.99 17.15 7.21

Female High frequency

n

Low frequency

644.70 578.33 596.98 469.77 457.02 509.75

4 8 9 II 4 2 3

161.80 141.11 128.53 123.90 126.40 124.10 111.30

. ± -t± ± ± ±

38.77 100.36 202.25 184.70 114.59 29.34

-----+ ± -+

11.97 20.81 18.18 26.10 14.68 11.17 27.98

High frequency 1,062.35 1,076.06 931.10 809.24 827.80 673.75 639.97

± --. ± ± ± ±

154.04 315.50 299.30 191.19 266.62 31.47 146.70

RESULTS

Jitter during sustained vowels The means and SDs for jitter during sustained vowels are contained in Tables 4 and 5. The mean perturbation of both male and female subjects was < I% of the Fo that is considered normal, according to Hirano (17). The one exception was the group of two men aged 70-79 years whose jitter values were >1%.

The means and SDs for all acoustic, aerodynamic, and videostroboscopic data are presented in table form. The means that lie outside the expected value, based on published normative data, are indicated with an asterisk.

Fo during reading Results from the current study are contained in Table 6. Compared to the normal data published in Colton and Casper (I), all of the data for the subjects in this study fell within the norms.

and Casper (1), Baken (18), Kent et al. (19), and Hirano (17). The purpose was to document the acoustic, aerodynamic, and videostroboscopic measures and signs that typically present with laryngeal fatigue.

F r e q u e n c y range

Acoustic analysis

F o during sustained vowels The means and SDs for the F0 values of 25 male subjects and 41 female subjects are shown in Table 2. According to Colton and Casper (1), the normal F0 are 100-150 Hz and 180-250 Hz for men and women, respectively. The results of the present study fell within this normal range. When comparing the results of the F0 values from different age ranges to the normative data (see Table 3), all male and female frequency levels also fell within normal limits, except for women ages 60-69 years. The means and standard deviations for the two female subjects in this age range were 169.65 9.83 Hz, which was lower than the norm of 202 Hz.

The means and SDs for frequency range are shown in Tables 7 and 8. According to normative data published in Hirano (17), all values appeared to fall within the normal range. Aerodynamic analysis

Flow volume The means and SDs for flow volume are contained in Tables 9 and 10. All values were within normal limits when compared with the norms published by Baken (18). Flow rate The means and SDs for flow rate are shown in Tables 11 and 12. When compared with the range

T A B L E 9. Means +- SDs for flow volume (ml) Comfort

High

Low

Sex

n

Mean - SD

n

Mean - SD

n

Mean - SD

Male Female

26 40

3,348.65 ± 977.02 2,358.30 ± 596.60

26 40

3,276.35 - 847.11 2,359.35 - 491.63

24 39

3,193.79 - 788.09 2,349.59 ± 513.30

Data obtained at comfortable-, high-, and low-pitch levels.

Journal of Voice, Vol. tO, No. 2, 1996

LARYNGEAL FATIGUE T A B L E 10. Means +- SDs f o r flow volume (ml) at

comfortable pitch compared by age in decades Age range (yr)

Male n

10-19 20-29 30-39 40--49 50-59 60--69 70-79

0 4 3 5 3 9 2

Female

Mean ±- SD -3,855.00 4,787.00 3,344.80 3,476.67 2,637.00 3,198.50

n

--+ 835.83 ± 961.41 ± 670.26 ± 492.28 -+ 846.33 -+ 153.44

4 8 9 10 4 2 3

Mean ± SD 2,674.25 2,597.63 2,618.56 2,302.00 2,119.25 1,238.50 1,771.00

± 414.97 -+ 404.02 -+ 578.70 ± 569.71 ± 522.71 ± 337.29 ± 457.35

for male and female average flow rates according to Hirano's (17) and Colton and Casper's (1) gathered norms, the data for all women fell within normal limits. However, the results for men at comfortable and high-pitch levels were >200 ml/s, which were above the norms. The results for men in the age ranges 30-49 and 70-79 years were also abnormally high.

Maximum phonation time The means and SDs of maximum phonation time are shown in Tables 13 and 14. Kent et al. (19) compiled a table of norms representing the means of several studies of maximum phonation time in seconds. The means from the present study demonstrated a lower-than-normal maximum phonation time for men and women in comfort, high, and low pitch levels. When maximum phonation time measures were averaged by subject age (in decades), the results showed lower-than-normal maximum phonation times for men in all age groups from 30 to 79 years and for women in the age groups 20-79 years. Videostroboscopic analysis Means and SDs of all videostroboscopic measures are contained in Tables 15 and 16. The means for all ratings were <2, indicating only slight deviation from normal with the exception of phase symmetry. The mean ratings for phase symmetry were slightly >2, indicating mildly asymmetrical closure.

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The most interesting results were shown in the breakdown of the different types of glottal closure observed during videostroboscopy. From the total of 36 men and 52 women, 29 subjects (10 men and 19 women) demonstrated an anterior glottal chink. Three subjects presented with both an anterior and a posterior glottal chink. A spindle-shaped closure was observed in 22 subjects (17 men and 5 women). Fifteen of these 22 subjects (12 men and 3 women) were 60 years old or older. Twenty-three of the 88 subjects presented with a posterior chink; however, 19 of these were women, and a small posterior chink found in women is considered normal (1,20). Only four men presented with a posterior glottal chink. Seven subjects presented with complete closure. Incomplete closure was observed in four subjects. Given that a posterior glottal chink is considered normal in women, the vast majority of subjects presented with an abnormal anterior chink, an abnormal anterior and posterior chink, or an abnormal spindle-shaped closure. Summary of objective measures that deviated from the n o r m

There were few deviations from the norm found in the results of the acoustic measures. Means and SDs ofF0 during a sustained vowel production were lower than expected only for two women in the age range of 60-69 years. The results of jitter during sustained vowel production were normal except for two men in the age range of 70-79 years, who presented with values slightly higher than the norm. Several more consistent abnormalities were found in the aerodynamic and videostroboscopic measures. The mean values for flow rate for all men at comfort and high pitch levels were higher than the average 200 ml/s. Men in the age ranges of 30-50 and 70-79, demonstrated a higher-than-expected flow rate. The mean maximum phonation times for all subjects at all pitch levels were shorter than expected. Subjects in all age ranges except the youngest

T A B L E 11. Means +- SDs f o r flow rate (ml/s) Comfort

High

Low

Sex

n

Mean ± SD

n

Mean - SD

n

Mean ± SD

Male Female

25 40

*202.68 ± 88.74 143.13 ± 54.24

25 40

*237.20 ± 108.36 173.92 ± 77.54

23 39

192.78 ± 94.25 140.73 ± 68.86

Data obtained at comfortable-, high-, and low-pitch levels. Values considered outside the normal range are indicated by an asterisk.

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DISCUSSION

sions tended to be among those requiring extensive voice use. The Herrington-Hall et al. (21) study listed a category called "normal on exam" for subjects who presented with dysphonia in the presence of a normal larynx. It could be speculated, based on the current research, that this category may have included some subjects with laryngeal fatigue that was not detected through mirror examination of the vocal folds. Finally, Herrington-Hall et al. (21) found a high occurrence of older subjects presenting with laryngeal pathologies. Seventy-eight percent of their patients were older than 45 years, with 22% being 64 and older. The effects of aging in the present investigation should not be overlooked. When data were compared with norms, decreased Fo was found only in the two 60- to 69-year-old women, increased jitter only in the male group aged 70-79, and a high percentage of spindle-shaped glottal closure in the 60- to 69-year-old men. The objective and subjective measures gathered for this study revealed several patterns of abnormalities that may be related to the complaint of laryngeal fatigue. The three most consistent measures that were found to be abnormal were high airflow rate, decreased maximum phonation time, and the large number of subjects presenting with anterior, anterior and posterior, and spindle-shaped glottal chinks.

The present retrospective study addressed objective measures of voice production from patients complaining of laryngeal fatigue in the absence of other laryngeal pathologies. Acoustic, aerodynamic, and videostroboscopic data were then compared to published norms in order to determine which measures and signs of voice production would most likely present when laryngeal fatigue was the complaint. It was interesting to note that 10 of the 12 most common occupations held by the subjects in this current investigation were considered at high risk for laryngeal pathologies, as reported by Herrington-Hall et al. (21). These "high-risk" profes-

Comparison of data with previous studies of laryngeal fatigue The majority of the previous studies of laryngeal fatigue examined only s u b j e c t i v e m e a s u r e s . Koufman and Blalock (9) and Greene (3) reported evidence of a breathy voice with laryngeal fatigue. The current findings of increased flow rates in patients complaining of voice fatigue would support the presence of breathiness. Colton and Casper (l) described symptoms of being vocally tired, a feeling of tightness, difficulty in talking loudly, and talking in monopitch. When the glottis is not completely closing, more effort will be required to produce loud voice, thus weakening or straining the laryngeal

T A B L E 12. Means +- SDs for flow rate (ml/s) at

comfortable pitch compared by age in decades Male

Age range (yr)

n

10-19 20-29 30-39 40--49 50-59 60--69 70-79

0 4 3 5 3 8 2

Female

Mean +- SD -143.75 *280.67 *250.40 175.33 169.63 *257.50

± ... ± -

n

-48.02 150.51 104.03 20.40 67.60 12.02

4 8 9 10 4 2 3

Mean ± SD I 11.33 144.50 151.08 147.90 166.00 92.00 145.67

± 13.77 ± 19.89 ± 71.32 +- 63.81 +-- 81.07 ± 0 ± 32.56

Values considered outside the normal range are indicated by an asterisk.

groups (age 10-19 years for women and 10-29 for men) demonstrated shorter-than-average maximum phonation times. The videostroboscopic measures deviated from the norm in phase symmetry, where the results showed the vocal folds of all subjects to be slightly asymmetrical. A more consistent finding was abnormal glottal closure. Thirty-three percent of the subjects were observed to present with an anterior glottal chink, 3% presented with an anterior and posterior glottal chink, and 25% of the subjects presented with a spindle-shape configuration.

T A B L E 13. Means +- SDs for maximum phonation time (s) Comfort

High

Low

Sex

n

Mean +- SD

n

Mean ± SD

n

Mean +- SD

Male Female

26 40

"19.16 --- 8.51 *18.08 ± 6.42

26 40

"15.96 --- 7.82 "16.09 ± 6.82

24 39

*20.34 --- 10.46 "19.73 ± 7.77

Data obtained at comfortable-, high-, and low-pitch levels. Values considered outside the normal range are indicated by an asterisk.

Journal of Voice, Vol. tO, No. 2, 1996

LAR YNGEAL FATIGUE

T A B L E 14. Means +-- SDs for maximum phonation

times (s) at comfortable pitch compared by age in decades Male

Age range (yr)

n

10-19 20-29 30-39 40--49 50-59 60-69 70-79

0 4 3 5 3 9 2

Female

Mean -+ SD -28.70 "21.50 "15.86 *20.33 "17.07 "12.45

+--+-

n

-8.07 12.28 7.00 5.32 7.84 .07

Mean +- SD

4 8 9 10 4 2 3

24.13 "18.64 '18.61 "17.95 "16.20 "13.45 "12.97

- 3.08 -+ 4.99 -+ 5.96 -+ 7.36 - 9.63 +- 3.61 - 5.15

Values considered outside the normal range are indicated by an asterisk.

muscles. Some patients may complain of feeling tension, thickness, or "lump in the throat." Although several previous studies examined F0 as it related to laryngeal fatigue, the current study showed no relationship between laryngeal fatigue and abnormal pitch. All subjects appeared to be within normal limits for F0 and frequency range. Koufman and Blalock (9) found a relationship between low pitch and laryngeal fatigue, whereas Sander and Ripich (11) and Colton and Casper (1) reported that speakers with fatigue showed difficulties at both the high and low end of the pitch range. Comparison of data with previous studies on experimentally induced laryngeal fatigue Subjects of the present study were composed of actual patients who complained of laryngeal fatigue. In comparing the findings of the current study to those in the four previous studies in which laryngeal fatigue was experimentally induced by prolonged

153

reading (13-16), the most significant parallel was seen in the consistent finding of incomplete glottal closure. A vast majority of the subjects in the current study presented with anterior, anterior and posterior, or spindle-shaped glottal chinks (61%). Thirtythree percent of the total number of subjects, which included 37% of the women and 28% of the men demonstrated an anterior glottal chink; 3% presented with anterior and posterior chinks; and 25% presented with a spindle-shaped closure. In reviewing the videostroboscopy tapes from this study, it was clear that those subjects with both anterior and posterior glottal chinks did not present with edema, which would have been more characteristic of the hourglass-shaped glottal closure; rather, the observation was clearly that of an anterior and posterior chink. The presence of anterior glottal chinks in healthy subjects following prolonged reading led Stemple et al. (16) to question "whether there may be a continuum of functional muscular weakening and the possibility that an anterior chink might be a diagnostic sign of laryngeal fatigue." We may further speculate that other glottal configurations develop as the musculature weakens, leading to more severe symptoms of vocal fatigue. A study correlating perceptual characteristics, degree of fatigue (as judged by the patient), and the glottal configuration may clarify these relationships. Objective measurement of laryngeal muscle weakness is problematic. The literature relating to laryngeal fatigue continues to suggest, however, that the symptoms of voice fatigue are related to muscle weakness caused by voice abuse, misuse, or overuse. In the present

T A B L E 15. Means +- SDs o f eight subjective videostroboscopic measures

Sex

n

Supraglottic activity

Male Female

36 52

1.64 --+ 1.10 1.02 +-- .94

Vertical level approximation 0 0

Vocal fold edge

Amplitude

L

R

L

R

.38 -'- .49 .08 +- .27

.44 + .56 .08 -+ .27

1.81 --- .62 1.73 ± .69

1.89 --- .52 !.67 +- .64

N onvibrating portion

Mucosal wave Sex

L

R

L

R

Phase symmetry

Phase closure

Male Female

1.22 --- .64 .94 +-- .78

1.25 - .65 .92 -+ .76

0 0

.03 +-- .17 0

2.5 +- 1.13 2.65 -+ 1.03

- 1.89 --- 1.67 - 1 . 6 0 -+ 1.54

The first seven measures are based on a 6-point scale (0-5; 0 = normal; 5 = severe deviation from normal). Phase closure is based on an ll-point scale [ - 5 to 5; - 5 = open phase predominates (whisper/dysphonia); 5 = closed phase predominates (glottal fry, extreme hyperadduction); 0 = normal]. L, left; R, right.

Journal of Voice, Vol. 10, No. 2, 1996

154

C. S. E U S T A C E ET AL. TABLE

16. Glottic closure configurations for 88 subjects compared by age in decades Male

Age range (yr)

n

Complete

Posterior (P)

10-19 20-29 30-39 40--49 50-59 6(I--69 70-79 80-89 Total

2 4 4 6 5 11 3 1 36

--2 1 I ---4

2 I I -----4

Female Anterior (A)

Spindle . 1 -3 1 8 3 I 17

.

. I I 2 3 3 --10

Incomplete

n

Complete

I ------1

4 10 1I 12 6 2 7 0 52

----I -2 . 3

. -------0

study, higher airflow rates and decreased maximum phonation times in the presence of abnormal glottal configurations appear to support this hypothesis.

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A/P

Posterior (P) 2 7 5 2 3 --.

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