Clinical report on preliminary data on intraoral pressure in the evaluation of laryngeal pathology

Journalof Voice Vol. 6, No. 1, pp. 79-85 © 1992RavenPress, Ltd., New York

Clinical Report on Preliminary Data on Intraoral Pressure in the Evaluation of Laryngeal Pathology Kazutomo Kitajima and Fumika Fujita Department of Otolaryngology, Shiga University of Medical Science, Seta, Otsu, Japan

Summary: The consonant/b/, when surrounded by vowels, is accompanied by vocal fold vibration even during occlusion of the supraglottal cavity. Since the voicing of/b/ involves a relatively loose closure of the glottis and smaller amplitudes of vibration than those observed during the production of vowels, the transglottal pressure during/b/production approximates that of the oscillation threshold pressure. Since the intraoral pressure of/p/ production is approximately equal to subglottal pressure of the surrounding vowels, the differences in peak intraoral pressure between the productions of/i:pi:/and /i:bi:/can be assumed to reflect the transglottat pressure during/b/production. In a clinical investigation, the differences in the peak intraoral pressures of /i:pi:/and/i:bi:/were found to be higher in conditions typified by stiff vocal folds, such as laryngeal cancer and partial laryngectomy, than in those typified by flaccid folds, such as vocal cord polyp and palsy. This suggests that the intraoral pressure differences between/i:pi:/and/i:bi:/ may constitute a parameter indicative of vocal cord stiffness. Key Words: Laryngeal function-Subglottal pressure--Intraoral pressure--Stiffness of the folds.

In his study of small-amplitude vocal fold oscillations, Titze (1) used the term "oscillation threshold p r e s s u r e " to indicate the minimum degree of lung pressure necessary to initiate vocal fold vibration when the vocal folds are slightly abducted. The oscillation threshold pressure appears to be directly related to such laryngeal factors as the thickness of the folds, their viscosity, the wave velocity of the mucosa, a n d glottal width, since the oscillation threshold pressure forms in a linear relation with these factors. Verdolini-Marston et al. (2), who designed a method of measuring the oscillation threshold pressure in humans, detected increases in pressure when the folds were dehydrated, suggesting that the oscillation threshold pressure might be of clinical value in determining the ease with which phonation is a c h i e v e d and sustained. VerdoliniM a r s t o n ' s m e t h o d o f measuring the oscillation

threshold pressure requires the patient to phonate at three levels of intensity: just above the minimum threshold, just below, and between the two. The complexity of the procedure suggests that it might be impractical for clinical use, however, as the ordinary patient might have difficulty distinguishing the rather fine phonetic adjustments involved. In view of this, we directed our attention to the transglottal pressure during p l o s i v e s / b / a s a possible substitute for the oscillation threshold pressure. The c o n s o n a n t / b / , when surrounded by vowels, is accompanied by vocal fold vibration even during occlusion of the supraglottal cavity (3). Since the voicing o f / b / i n v o l v e s a relatively loose closure of the glottis (4,5) and smaller amplitudes of vibration than those observed during the production of vowels (6), the transglottal pressure d u r i n g / b / p r o d u c tion approximates that of the oscillation threshold pressure. The present study was an attempt to determine whether this parameter would yield results similar to the oscillation threshold pressure in identifying abnormalities in vocal fold function. We

Address correspondence and reprint requests to Dr. Kitajima at Department of Otolaryngology, Shiga University of Medical Science, Seta, Otsu, 520-21 Japan. 79

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K. K I T A J I M A A N D F. F U J I T A

would like to emphasize that this is still a preliminary study investigating the potential of the technique rather than its validity as a clinical tool. A more objective evaluation of the accuracy of our method will be performed using a miniaturized transducer now under order. The transglottal pressure during /b/ production was estimated noninvasively by calculating the difference between the peak intraoral pressures during the productions of/i:pi:/and/i:bi:/. Our reasoning was as follows: When the voiceless consonant/p/is interpositioned between vowels, as in /i:pi:/, the peak intraoral pressure of/p/(abbreviated as pr./p/) is approximately equal to the subglottal pressure of the surrounding/i/'s (7-9). However, the peak intraoral pressure of the voiced consonant/b/(abbreviated as pr./b/) does not reach this level (10-13). In b o t h / p / a n d / b / , the subglottal pressure is approximately the same, and remains at a steady level if the surrounding vowels are uttered at the same intensity (14-16). Since, as mentioned above, pr./p/ is roughly equivalent to the subglottal pressure, and since the subglottal pressure is the same during the production of both/i:pi:/and/i:bi:/, the difference between pr./p/and pr./b/ (abbreviated as pr./p-b/) can be assumed to represent the pressure differential necessary for the voicing of/b/. Vowel production in normal vowel speakers involves relatively small flows of air through the upper airway, so that the estimation of transglottal pressure differences is fairly precise (8). In subjects with pathological vocal folds, however, larger than normal air flows create additional pressure in the supraglottal cavity, so that a certain percentage of the oral pressure must be subtracted in order to obtain an accurate estimate of the pressure difference. The influence of this additional pressure can be eliminated through the calculation of pr./p-b/(the difference between the peak intraoral pressure of /i:pi:/and/i:bi:/), as I will explain with reference to Fig. 1, illustrating the pressure gradients during /i:pi:/production (left) and/i:bi:/production (right). The uppermost horizontal line (pr./p/) represents the magnitude of estimated subglottal pressure. Placing the magnitude of pressure created by the larger than normal airflow at line pi, the transglottal pressure during/i/production can be calculated by subtracting pi from pr./p/. During/i:bi:/production, the magnitude of peak intraoral pressure (pr./b/) is smaller than the pr./p/, due to the continued adduction of the folds. Hence the subtraction of pr./b/

Journal of Voice, Vol. 6, No. 1, 1992

/i:pi:/

/i:bi:/

prlpl transglottal , pressure of /i/~, pr.lp-bl I

p~Ibl

pi

..... i

FIG. 1. The pressure gradients during/i:pi:/production (left) and /i:bi:/production (right). The pr./p/represents the magnitude of estimated subglottal pressure. Placing the magnitude of pressure created by the larger than normal airflow at line pi, the transglottal pressure during/i/production can be calculated by subtracting pi from pr./p/. During /i:bi:/ production, the pr./b/ is smaller than the pr./p/. The subtraction of pr./b/from pr./p/(pr./ p-b/) eliminates pi.

from pr./p/(pr./p-b/) eliminates pi, the pressure created by the high airflow. Figure 2 is a stylized tracing of intraoral pressures during /i:pi/ and /i:bi/ typically observed in our study as well as in previous studies (7,17). The intraoral pressure during /i:bi:/ production shows a gradual increase following the closure of the lips and drops with the lips' opening. This signifies that the transglottal pressure decreases during /i:bi:/ production just prior to the start of the second/i/. The difference between pr./p/and pr./b/was subjected to further analysis, our concern being with the smallest transglottal pressure (i.e., pr./p-b/ value) at the time of vocal fold vibration (Fig. 2). This pressure is believed to approximate the oscillation threshold pressure, as explained above, but to approximate it on the side of excess since the closed lips are probably open before the transglottal pressure lowers to the value of the oscillation threshold pressure. The pr./p-b/values were measured in several subjects with pathological conditions of the larynx involving both abnormal stiffness and abnormal flaccidity. The values obtained were compared with pr./p/ (representing the approximate subglottal pressure during the steady phonation of vowels) in

INTRAORAL PRESSURE IN LARYNGEAL PATHOLOGY 100 i

rnsec

81

i

VOICE -

FIG. 2. Estimation oftransglottal pressure during/b/production.

A

INTRAORAL PRESSURE i

p

i

i

b

i

A : peak intraoral pressure of / p / : transglottal pressure B : smallest transglottat pressure

breath. The intensity o f / i : / w a s checked at a distance of 20 cm from the lips. Five utterances of /i:bi:/ were then made in the same manner, with care being taken to maintain the same level of intensity and pitch as in the/i:pi/trial. The second, third, and fourth utterances of/i:pi:/and/i:bi/were used for further analysis. The mean values of the three peak intraoral pressures of/i:pi:/(abbreviated as Pr./p/) and three peak intraoral pressures of/i:bi:/(abbreviated as Pr./b/) were then determined. The pressure difference between Pr./p/and Pr./b/was defined as Pr./p-b/. The mean value of the three flow rates (abbreviated as MFR) was determined at the vowel/i:/ section of /i:pi:/. The oral flow rate was measured with a face mask, and the intraoral pressure with a polyethylene tube placed in the corner of the mouth (Fig. 3). The signals from the pressure and flow transducers (Pneumotachometer Type 9104; SAN-E1 Instrument Co.) were transcribed onto a paper oscillograph (Type MS6; SAN-E1 Instrument Co.).

order to determine the potential of this new parameter for identifying abnormal vocal fold function. Our aforementioned difficulties in applying Verdolini-Marston's technique to patients with pathological larynges prevent a comparison of our results with hers; an objective evaluation of the accuracy of our methods will be performed using a miniaturized transducer now under order. SUBJECTS A total of 65 subjects were tested: 14 normal controis, 10 laryngeal cancer patients (four Tl's, four T2's and two T3's), 21 polyp patients (including polypoid vocal folds), 14 unilateral vocal folds palsy patients, and six partial laryngectomy patients. METHODS Each subject was asked to produce five utterances of/i:pi:/at a comfortable pitch and intensity, with each utterance being performed in a single

BLOCK

DIAGRAM Peak Oral Pressure ~

voice

PNEUMOTACHOMETER

. . . .

I 'qllllltllfflllrq~

Pressure

SAN-E=

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FIG. 3. Block diagram of the system.

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K. K I T A J I M A A N D F. F U J I T A

Preliminary test Since subglottal pressures increase in accordance with the intensity of phonation (18-20), it is believed that the intraoral pressures o f / p / and /b/ might be similarly affected. Thus, the test must be carried out within certain limits of intensity in order to insure greater accuracy. In the preliminary test, six normal subjects (four males and two females) were asked to utter/i:pi:/and/i:bi:/at a comfortable pitch and intensity. The mean intensity observed in this test was 82.4 dB, with a standard deviation of 1.9; the range determined by the mean --- SD was 81-84 dB. Only subjects who could produce these utterances within this range of intensity were analyzed in our study. The intensity of voicing during /b/itself was not monitored, based on the assumption that if the intensity of the proceeding vowel remained within a certain range, the intensity of voicing o f / b / w o u l d also be within a certain range. RESULTS The mean values of Pr./p-b/, Pr./p/, and MFR in normal subjects were 4.8 cm H20 (SD = 2.2), 11.0 cm HzO (SD = 1.9) and 96 ml/s (SD = 22), respectively. There were no differences between males and females. The normal ranges, defined for the purpose of this study as the mean +-- 2 SD, were 0.4-9.2 cm H20 for Pr./p-b/, 7.2-14.8 cm H20 for Pr. /p/, and 52-140 ml/s for MFR. The values of Pr./p/coincided well with those of previous investigators who used the same methods for data collection [12.6 cm HzO (10); 11.6 cm H20 (13)]. The oscillation threshold pressure reported in VerdoliniMarston's study (2) was 3.50 cm HzO on average, which was lower than our Pr/p-b/ value; as explained above, this result was not unexpected. Comparison between normal and diseased subjects Figure 4 shows the distribution of Pr./p-b/values for each of the pathological conditions examined. Six out of 10 cancer subjects and all six of the partial laryngectomy patients displayed values in excess of the normal range (9.2 cm H20 shown by the dotted line). Statistically significant increases in Pr./ p-b/values (Wilcoxon test, p < 0.01) were seen in cases of cancer and partial laryngectomy. No significant deviation from the normal was observed in polyp or palsy cases. Figure 5 shows the distribution of Pr./p/for each of the pathologic conditions studied. Nine out of 10

Journal of Voice, Vol. 6, No. 1, 1992

Pr./p-b/

( cm H 2 0 )

h 10

i

CANCER

20

~ 3,0

i

%,8,,o0 / t

o

o o

i

i ~co o

PARTIAL LARYNGECTOMY

POLYP

o

o oo o~8oo oo o,o o °°tt

o

o oo

i

PALSY

o

0o8o

o ooo I oo ',

o

FIG. 4. The distribution of Pr./p-b/for each pathologic condition. The dotted line shows the upper limit of the normal range (9.2 cm H20).

cancer cases and all of partial laryngectomy cases showed values that were larger than the normal range (14.8 cm HzO). These values were statistically larger than those of normal subjects (Wilcoxon test, p < 0.01). The values of polyp and palsy cases were also larger than those of normal subjects (Wilcoxon test, p < 0.01). Figure 6 shows the distribution of MFR. Most subjects with pathologies showed the larger values than the upper limit of the normal range (140 ml/ sec).

Comparison between the respective pathologic conditions A comparison was made of the values of Pr./p-b/, Pr./p/, and MFR in the four types of pathologic conditions studied. Tables 1-3 shows the results of Pr./ p-b/, Pr./p/, and MFR. Asterisks indicate the presence of a statistically significant difference between two corresponding types (Wilcoxon test, p < 0.01). Pr./p-b/ values tended to fall into two groups, with cancer and partial laryngectomy patients showing higher values than palsy and polyp patients Pr./p/(cmH20) 10

I

20

30

i o,' o°° o o o

CANCER

40

50 o

60 o

PARTIAL LARYNGECTOMY

POLYP

PALSY

o ~oo

oo

',o oooo

'o~

r i 8!OOOo ~o

o o

ooooo

FIG. 5. The distribution of Pr./p/for each pathologic condition. The dotted line shows the upper limit of the normal range (14.8 cm HzO).

1NTRAORAL PRESSURE IN LARYNGEAL PATHOLOGY M F R (ml/sec) 100 CANCER

oo

200

I

300

,, o',i ,~o oo

400

500

600

TABLE 2. Difference in Pr./p/ among four types of diseases

o

i

i pARTIAL LARYNGECTOMY

POLYP

i I i

Palsy oo

o

o

o

o

PALSY

o

o

o

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oo

o

o

o

o

o o

oo

o

Polyp

Partial laryngectomy

Cancer

Cancer Partial laryngectomy Polyp Palsy

i i o ,5o~o~%

83

oo

o

FIG. 6. The distribution of MFR for each pathologic condition. The dotted line shows the upper limit of the normal range (140

a Significant difference between the corresponding diseases (Wilcoxontest, p < 0.01).

ml/s). (Wilcoxon test, p < 0.01). No similar differences were found between these two groups in the values of Pr./p/. A difference was observed between the MFR values in patients with polyps and those with palsies, a distinction that did not occur in Pr./p-b/. Cancer and partial laryngectomy patients are characterized histopathologically by vocal folds of above-average stiffness, whereas polyp and vocal fold palsy patients are characterized by vocal folds of abnormal flaccidity (21). The differing Pr./p-b/ values in the cancer-partial laryngectomy group and the polyp-palsy group are thought to reflect this pathological phenomenon.

plained above, whereas Pr./p/and MFR are so influenced. DISCUSSION

Three out of the 14 patients with palsy were tested both before and after voice recovery. In Fig. 7, the changes in Pr./p-b/, Pr./p/, and MFR are shown. Cases 1 and 3 show spontaneous voice recovery, and case 2 had Isshiki's thyroplasty (22). In these three subjects, the values of Pr./p-b/showed no changes in spite of notable decreases in the values of Pr./p/and MFR. This suggests that Pr./p-b/is a parameter independent of Pr./p/and MFR. This independence may be due to Pr./p-b/not being influenced by larger than normal airflow rates, as ex-

The present study is in many ways a preliminary report; we are continuing our investigation with a larger number of subjects and pathological conditions. In addition, our department will soon be in possession of a miniaturized transducer sensitive enough to take direct reading of the subglottal pressure and transglottal pressure, enabling an accurate and objective evaluation of our method for etimating the oscillation threshold pressure. Nevertheless, we believe that our results to date are indicative enough to warrant a discussion of the related issues. The majority of the patients in our study recorded higher than normal Pr./b/ values, a phenomenon that is generally attributed to the additional pressure needed to produce sound in pathologically affected larynges. In the case of the polyp and palsy patients, the rises in Pr./b/ values corresponded quite closely with the rises in Pr./p/values, leading to quasi-normal results in the Pr./p-b/parameter for both conditions. In the cancer and partial laryngectomy patients, however, the increases in Pr./b/were

TABLE 1. Difference in Pr./p-b/ among four types of diseases

TABLE 3. Differences in MFR among four types of diseases

Pre- and posttherapy comparison

Palsy

Polyp

Partial laryngectomy

Palsy

Cancer

Polyp

Partial laryngectomy

Cancer

Cancer Partial laryngectomy Polyp Palsy

Cancer Partial laryngectomy Polyp Palsy

" Significant difference between the corresponding diseases (Wilcoxon test, p < 0.01).

" Significant difference between the corresponding diseases (Wilcoxon test, p < 0.01).

a

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84

K. K I T A J I M A A N D F. F U J I T A cmH20 30

I

8.8

• Pr. /p/

I

20 I

o Pr. /b/

0..

I Pr. / p - b /

I

6

8 8.2

lO

6 8

853~158

Case 1

534~185

Case 2

411 ~187

MFR (ml/sec)

Case 3

FIG. 7. The changes in Pr./p/, Pr./p-b/, and MFR before and after treatment in three subjects with palsy. The intraoral pressure is scaled vertically, and the changes in the pressures between the two tests are shown by the arrows. Solid circles indicate Pr./p/, and open circles represent Pr./b/. The length of the dotted vertical line connecting these two circles represents the value of Pr./p-b/. The changes of MFR's in three subjects are shown at the bottom of the graph.

unable to compensate for the very large rises in Pr./p/, resulting in much higher values for Pr./p-b/. In normal subjects, two factors are involved in the intraoral pressure differences b e t w e e n / p / a n d /b/ (Pr./p-b/ in this study): the size of the supraglottal cavity (larger during the production of/b/), and the width of the glottis (smaller during the production of/b/) (10,17,23-26). In subjects with pathological vocal folds, high subglottal pressure can also be assumed to exert a considerable influence on Pr./pb/. The question remains, however, as to which of these factors is most significant in the determination of abnormal Pr./p-b/values. Supraglottal cavity size seems an unlikely candidate: It is improbable that the cavity could be opened wide enough to occupant for the larger differences seen in Pr./p-b/values in cancer and partial laryngectomy patients. There is, furthermore, no research to suggest that such patients show abnormally large expansion of the supraglottal cavity during/b/production. Pathologically limited vocal fold movement, which might influence the difference in glottal width between/p/ and/b/production did not appear to be determinaJournal of Voice, Vol. 6, No. 1, 1992

tive. The palsy cases, for example, showed no significant alteration in their Pr./p-b/values following therapy and the restoration of normal laryngeal function (indicated by reduced Pr./p/and MFR values) (Fig. 7). Nevertheless, we understand that the actual differences in glottal width b e t w e e n / p / a n d /b/have to be studied in both normal and pathological larynges in order to properly evaluate the role of glottal width. Hence, the abnormally high subglottal pressure found in pathological conditions can be assumed to be the decisive factor. The fact that subjects with high Pr./p/(estimated subglottal pressure) did not always show high Pr./p-b/does not refute this conclusion: In patients of this type---primary vocal fold palsy patients--the Pr./p/was boosted by high airflow, whereas the Pr./p-b/was not. Diagnostically speaking, the most distinctive difference in the laryngeal conditions of cancer/partial laryngectomy patients and polyp-palsy patients is that the former group displays vocal folds which are highly stiff, whereas the latter group has vocal folds which are abnormally flaccid. The results of the former group of patients suggests that the stiffness is responsible for the altered relationship between Pr./p/and Pr./b/reflected in the higher values obtained for Pr./p-b/. Hence, this parameter might serve as an indication of pathological conditions that result in high stiffness of the vocal folds. REFERENCES 1. Titze IR. The physics of small-amplitude oscillation of the vocal folds. J Acoust Soc A m 1988;83:1536-52. 2. Verdolini-Marston K, Titze IR, Druker DG. Changes in phonation threshold pressure with induced condition of hydration. J Voice 1990;4:142-51. 3. Sawashima M, Abramson AS, Cooper FS, Lisker L. Observing laryngeal adjustments during running speech by use of a fiberoptic system. Phonetica 1970;22:193-201. 4. Hirose H, Gay T. The activity of the intrinsic laryngeal muscles in voicing control. Phonetica 1972;25:140--64. 5. Hirose H, Ushijima T. Laryngeal control for voicing distinction in Japanese consonant production. Phonetica 1978;35: 1-10. 6. Sawashima M. Movements of the larynx in articulation of Japanese consonant. University of Tokyo: Annual Bulletin o f the Research Institute o f Logopedics and Phoniatrics, 1968;2:11-20. 7. Shipp T. Intraoral pressure and lip occlusion in mid vocalic stop consonant production. Journal o f Phonetics 1973;1: 167-70. 8. Smitheran JR, Hixon TJ. A clinical method for estimating laryngeal airway resistance during vowel production. J Speech Hear Dis 1881;46:138-46. 9. Kitajima K, Fujita F. Estimation of subglottal pressure with intraoral pressure. Acta Otolaryngol (Stockh) 1990;109: 473-8.

INTRAORAL PRESSURE IN LARYNGEAL PATHOLOGY 10. Isshiki N, Ringel R. Air flow during the production of selected consonants. J Speech Hear Res 1964;7:233--44. 11. Subtelny JD, Worth JH, Sakuda M. Intraoral pressure and rate of flow during speech. J Speech Hear Res 1966;9:498518. 12. Murry T, Brown WR Jr. Peak intraoral pressures in whispered stop consonants. Journal o f Phonetics 1976;4:183-7. 13. Stathopoulos ET. Relationship between intraoral air pressure and vocal intensity in children and adults. J Speech Hear Res 1986;29:71--4. 14. Kuroki K. Subglottal pressure of normal and pathologic larynges. Practica Otologica (Kyoto) 1969;15(suppl 1):54-74. 15. MacGlone RE, Shipp T. Comparison of subglottal pressures associated w i t h / p / a n d Po/. J Acoust Soc A m 1972;51:664-5. 16. Murry T, Brown WS Jr. Aerodynamic interactions associated with voiced-voiceless stop consonants. Folia Phoniatrica 1979;31:82-8. 17. Netsell R. Subglottal and intraoral air pressures during the intervocalic contrast o f / t / a n d / d / . Phonetica 1969;20:68-73. 18. Isshiki N. Regulatory mechanism of vocal intensity variation. J Speech Hear Res 1964;7:17-29. 19. Tanaka S, Gould WJ. Relationships between vocal intensity

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21. 22. 23. 24.

25. 26.

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and noninvasively obtained aerodynamic parameters in normal subjects. J Acoust Soc Am 1983;73:1316-21. Holmberg EB, Hillman RE, Perkell JS. Glottal airflow and transglottal air pressure measurements for male and female speakers in soft, normal and loud voice. J Acoust Soc A m 1988;84:511-29. Kakita Y, Hirano M, Kawasaki H, Matsushita H. Schematical presentation of vibration of pathologic vocal cords. J Otolaryngol Jpn 1976;79:1533--48. Isshiki N, Okamura H, Ishikawa T. Thyroplasty type I (lateral compression) for dysphonia due to vocal cord paralysis or atrophy. Acta Otolaryngol (Stockh) 1975;80:465-73. Arkebauer HJ, Hixon TJ, Hardy JC. Peak intraoral pressure during speech. J Speech Hear Res 1967;10:196-208. Warren DW, Wood MT. Respiratory volumes in normal speech: a possible reason for intraoral pressure differences among voiced and voiceless consonants. J Acoust Soc Am 1969 ;45:466-9. Kent RD, Moll KL. Vocal-tract characteristics of the stop cognates. J Acoust Soc Am 1969;46:1549-55. Westbury JR. Enlargement of the supraglottal cavity and its relation to stop consonant voicing. J Acoust Soc A m 1983; 73:1322-36.

Journal of Voice, Vol. 6, No. 1, 1992