Velopharyngeal airway resistance disorders after traumatic brain injury

545

Velopharyngeal Airway Resistance Disorders After Traumatic Brain Injury Monica A. McHenry,

PhD

ABSTRACT. McHenry MA. Velopharyngeal airway resistance disorders after traumatic brain injury. Arch Phys Med Rehabil 1998;79:545-549. Objective: Disorders affecting velopharyngeal port closure may result in the perception of hypernasality. This study was designed to determine (1) the incidence of velopharyngeal airway resistance deficits after traumatic brain injury, (2) the relation between velopharyngeal airway resistance and dysarthria severity, and (3) the relation between velopharyngeal airway resistance and perceived hypernasality. Design: Case series. Setting: Community re-entry residential rehabilitation program. Patients: Eighty-three consecutive referrals for speech production evaluations. Main Outcome Measures: Velopharyngeal airway resistance at the time of the evaluation. Results: About half the patients evidenced reduced velopharyngeal airway resistance. Subjects who evidenced mild or absent dysarthria typically had no velopharyngeal deficits, while subjects who evidenced severe dysarthria had very low velopharyngeal airway resistance. With few exceptions, the severity of the velopharyngeal airway resistance deficit was associated with perceived hypernasality. Conclusions: Velopharyngeal airway resistance disorders after traumatic brain injury are common. Discrepancies between velopharyngeal airway resistance and perceived hypernasality may be caused by intelligibility, speaking style, or nonrepresentative sampling. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation PEECH PRODUCTION problems after traumatic brain injury (TBI) often involve multiple components that may S have interactive effects. For example, respiratory insufficiency may be exacerbated by velopharyngeal deficits. On the other hand, the interaction facilitates compensation for deficits along the vocal tract. Through a targeted assessment protocol, the contribution of each component to the speech problem may be determined. During the production of nonnasal sounds, the velopharyngeal port provides resistance to the flow of air through the vocal tract, shunting the air into the oral, rather than the nasal, cavity. The calculation of velopharyngeal airway From the Galveston Institute of Human Communication, Transitional Learning Community, Galveston, TX. Submitted for publication March 24, 1997. Accepted in revised form November 3, 1997. Supported by grants 94-23 and 96.3 from the Moody Foundation of Galveston, TX. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Monica McHenry, PhD, 1528 Postoffice Street, Galveston, TX 71553. 0 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003.9993/98/7905-4443$3.00/O

resistance provides an aerodynamic measure of the function of this speech subsystem and may provide insights into speech characteristics such as nasality. Interpretation of velopharyngeal airway resistance values remains somewhat subjective and based on clinical experience, although some objective data are available. In a pilot investigation,’ it was determined that velopharyngeal airway resistance values of <5Ocm H20/L/sec and/or nasal airflow values of > lOOcc/sectypically resulted in the perception of hypernasality by two expert listeners. These findings corroborated clinical experience. Results were not unequivocal, however. Additional research employing a larger sample, as well asnaive listeners, is underway. In this study, the above values are suggested as interpretative guidelines. Limited data are available regarding the incidence of hypernasality after TBI. In a sample of 20 subjects with severe TBI, Theodoros and colleagues2 found that 95% were perceived as hypemasal. There were discrepancies, however, between the perceptual data and the objective data obtained through accelerometric procedures.3 Further, the data were not related to dysarthria severity. Single case study reports4-7 often include hypernasality as a component of the patient’s speech production problem. This study was designed to address the following questions. What is the incidence of velopharyngeal airway resistance deficits in mild, moderate, and severe dysarthria associated with TBI? What is the relation between velopharyngeal airway resistance deficits and perceived hypernasality in individuals with TBI? METHODS Subjects The data were obtained from consecutive admissions to a residential community re-entry program as part of each patient’s speechproduction evaluation. Subjects were 56 men and 27 women who had incurred a severe TBI. Mean age for the men and women was 26.63 (17.02) and 26.55 (27.18) years, respectively. Mean months postinjury for the men and women was 48 (259) and 56 (283) months, respectively. Dysarthria severity was determined subjectively by the examiner during the clinical assessment.Judgments of severity were based on an oral peripheral evaluation, conversational speechsample, diadochokinetic rates, speech breathing analysis, voice evaluation, and intelligibility testing. Selected subject characteristics are provided in table 1. The intelligibility scores are based on the CAlDS sentence test* and the phonetic contrast test of Kent and colleagues.9 The intelligibility tests were judged by naive listeners who had not interacted with the subject. Scores are based on a single naive listener. Instrumentation To obtain the velopharyngeal airway resistance data, subjects wore a tight-fitting mask (Respironics”) over the nose, which was attached to a pneumotachograph (Hans Rudolph 4719b) and differential pressure transducer (Honeywell 163PC01D36C). Intraoral pressure was measured just inside the lips using a polyethylene catheter (inner diameter, 2mm) attached to a Arch

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Table

Subject

Arch

Dysarthria Presence

1

Yes

2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Yes Yes Yes Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

Phys

Med

1: Subject

Dysarthria Severity

Moderate Mild Severe Moderate Mild None None Moderate Mild Mild Mild Mild Severe Mild Mild Severe Mild Mild None Mild Mild Mild Severe Mild Mild Mild Mild Severe Mild Mild Severe Mild Severe None Mild Severe Mild Mild Mild None Mild Mild Mild Mild Mild Moderate Mild Mild Mild Severe Mild Mild Mild Mild Mild Severe Mild Mild Mild Moderate

Rehabil

AIRWAY

RESISTANCE,

Characteristics

Perceived Hypernasality

None Mild Mild Mild None None None Mild Mild None Mild None None Mild Mild Severe None Mild None None None Mild Severe None None None None Severe Moderate None Severe None Severe None Mild Severe Mild None None None None None None None None Moderate None Mild Mild Severe None Moderate None None None Severe Mild Moderate Moderate Mild

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Table Single Word Intelligibility

96 93

67 94 89 100 100 96 85 88 96 100 98 96 90 34 71 99 DNT 98 96 97 67 100 99 74 92 30 92 89 64 92 DNT 89 100 20 92 94 88 100 DNT 95 88 86 60 55 99 80 94 DNT DNT 90 93 90 94 78 99 97 82 88

sentence Intelligibility

85 100 22 100 90 100 100 68 92 95 97 100 36 84 86 40 88 95 DNT 97 93 93 a 96 87 100 99 DNT 81 DNT 65 93 DNT DNT 100 DNT 95 95 97 100 99 98 98 DNT 90 DNT 92 92 100 20 DNT 95 87 81 99 28 98 98 93 72

Rvp

92 100 36 42 47 100 96 a5 92 100 72 100 100 11 100 1 84 67 100 100 100 55 1 100 100 100 100 1 46 100 8 100 16 100 100 3 100 100 100 41 100 100 100 100 100 76 100 100 100 21 100 1 100 100 100 2 100 14 99 7

Subject

Dysarthria Presence

61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 Abbreviations: test.

Yes Yes Yes Yes Yes No Yes Yes Yes Yes No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes

1: Subject

Dysarthria Severity

Mild Mild Mild Mild Severe None Moderate Mild Mild Moderate None Mild Mild Severe Mild Severe None Moderate Moderate Severe Mild Severe Mild Fivp, velopharyngeal

Characteristics

(Cont’d)

Perceived Hypernasality

Single Word Intelligibility

None None None None Severe None Mild Mild None None None Mild None None Mild Severe None Mild Mild Severe None None Mild

93 90 96 94 16 100 62 95 72 99 100 86 90 45 88 79 100 87 88 75 96 89 86

airway

resistance;

Sentence Intelligibility

98 91 94 95 80 100 93 95 94 95 100 DNT 98 23 77 6 100 86 73 29 100 49 86

Rvp

84 49 57 100 14 100 96 49 100 100 100 53 87 100 100 11 49 93 100 46 100 100 97

DNT, did not

pressure transducer (Honeywell 162PC016c). The catheter was positioned behind the incisors so that its open tip was perpendicular to airflow and was not occluded by the tongue. Aerodynamic data were low-pass filtered at 20 Hz (Biocommunicationsd) and digitized at 3,571Hz. Tasks Subjects performed tasks to determine nasal cavity resistance including three trials each of quiet and deep breathing, sustained /m/ and /ma/ syllable trains. At a typical pitch and self-perceived habitual loudness, subjects then produced three /pi/ syllable trains at approximately 2 to 3 syllables/set. To facilitate smooth and consistent syllable production approximating conversational speech conditions, the subjects were instructed before each trial to “take a big breath.” The intended and most typical result approximated twice-tidal inspiration. If the subject inhaled excessively, the instructions were modified to elicit twice-tidal inspiration. The tasks were modelled and the subjects were provided with practice trials. If the examiner did not observe increased prephonatory inspiration followed by smooth and connected syllable production, the trial was retaken. Data were analyzed using automated software.e,f,lo,ll After the analyst chose the baseline token to be used to calculate nasal cavity resistance, the program extracted the velopharyngeal airway resistance mean. The three trials were averaged to determine the subject’s velopharyngeal airway resistance. Velopharyngeal airway resistance was calculated by dividing the peak intraoral air pressure during fpl production by the corresponding nasal airflow, and then subtracting nasal cavity resistance at the same nasal airflow.rl Nasal cavity resistance is the resistance provided by the nasal passage, including factors such as congestion and nasal passage configuration. During the tasks that measure nasal cavity resistance, the pressure/flow

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pressure

Intraoral

pressure

10 9 8

2 :,

Ll’i

i^t

Time

A

n

k

Time

Nasal airflow

Nasal airflow

:z;

0.8 8

0.6

3

0.4 0.2 0.0

Time Fig 1. Patient cm H*O/L/sec

with normal velopharyngeal producing /pi/ syllable trains.

Time airway

resistance

of 100

dynamics of the oral and nasal cavities are sampled with the velopharyngeal port open. Intraoral air pressure (P,) is compared with ambient or atmospheric pressure. A table is developed in the analysis software to establish the correspondence between P, and the resultant nasal flow. This regression function is then used as a subtraction factor when velopharyngeal airway resistance is calculated. Because nasal cavity resistance is subtracted in the calculation, the velopharyngeal airway resistance value reflects velopharyngeal port function, rather than being a composite indicator of nasal airway resistance. Velopharyngeal airway resistance, then, indicates the ability of the velopharyngeal port to prevent air from entering the nasal cavity. To determine intrajudge reliability, the baseline token chosen to represent nasal cavity resistance was remeasured and velopharyngeal airway resistance recalculated for ten subjects. There was no difference between the original and repeated measures. Examples of various velopharyngeal airway resistance values are provided in figures 1 through 3. Figure 1 displays normal airway velopharyngeal airway resistance of 1OOcm H20/L/sec. Strong intraoral pressure peaks are apparent and no nasal airflow is evident. The velopharyngeal port is providing good resistance to airflow, shunting it through the oral cavity. Figure 2 illustrates a low velophamgeal airway resistance of S8cm H,O/L/sec. The intraoral pressure peaks are markedly reduced, and the patient produced very high nasal airflows during buildup of pressure for the /p/ release. The descending peaks over time reflect reduced respiratory effort as the utterance progressed. Figure 3 illustrates a velopharyngeal timing deficit. Nasal airflow is high preceding the release of the plosive /p/, but returns to baseline levels at the /p/ release and during the subsequent vowel production. This patient would be perceived as producing nasal air emission, but nasal resonance would be within normal limits. RESULTS Data are reported for habitual loudness by functional groupings of velopharyngeal airway resistance values. Groupings are

Fig 2. Patient with reduced .58cm HZO/L/sec producing

velopharyngeal /pi/ syllable trains.

airway

resistance

of

based on clinical experience. A resistance value of 1OOcm HzO/L/sec is within normal limits. Values from 50 to 99 cm HzO/L/sec indicate a mild or inconsistent resistance deficit. Values from 25 to 49cm HzO/L/sec and values of <25 cm HzO/L/sec reflect moderate and severe deficits, respectively. Table 2 contains the data for men and women. Fifty-two percent of the patients evidenced velopharyngeal airway resistance within normal limits. Forty-eight percent evidenced reduced velopharyngeal airway resistance,ie, values of < IOOcm H2O/L/sec, with 17% evidencing a severe deficit. intraoral

:;L fl t

a 0

1 E 0

pressure -

6 4 2

::

0

Tir

Basal ; f.0 0.8 8 0.6 u) 3 0.4 0.2 0.0 Time Fig 3. Patient syllable trains.

with

velopharyngeal

Arch

timing

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/pi/

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2: Velopharyngeal

R’JP (cm H~OILlsec) 100 50-99 25-49 <25

Airway Resistance Men and Women

(Rvp)

AIRWAY

Men,No. (% of 56)

15(56%) 9(33%)

28(50%) 8(14%)

43(52%) 17 (20%)

9(16%) 11(20%)

14(17%)

3(11%)

OVerall, NO. (% of 83)

9 (11%)

Figure 4 displays dysarthria severity as a function of velopharyngeal airway resistance. It can be seen that most subjects with mild or no dysarthria evidenced velopharyngeal airway resistance estimates of 1OOcmH20/L/sec. By contrast, the majority of subjects with severe dysarthria evidenced velopharyngeal airway resistance estimates of <25cm HzO/L/ sec. Figure 5 illustrates perceived hypemasality as a function of velopharyngeal airway resistance. It should be reiterated that perceived hypemasality is based on the investigator’s judgment only, with the rating being completed before the velopharyngeal airway resistance value was known. It is possible that severity would be rated differently by larger, more varied groups of listeners. As expected, the majority of subjects with velopharyngeal airway resistance estimates of 1OOcm HzO/L/sec evidenced no perceived hypemasality. Subjects with velopharyngeal airway resistance estimates of <25cm HzO/L/sec were most often perceived as severely hypemasal. A few incongruous subjects such as the four who evidenced no perceived hypernasality despite velopharyngeal airway resistance estimates of 25 to 49cm HzO/L/sec will be addressed in the discussion. DISCUSSION In the present sample, about half of the subjects evidenced reduced velopharyngeal airway resistance. Seventeen percent had velopharyngeal airway resistance values of less than 25%, considered a severe deficit, and 13% of the subjects were

T fZZl

100

Fig 4. Dysarthria resistance.

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50-99

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Data for

Women, NO. (% of 27)

0

RESISTANCE,

deficit airway

4--50-99 Severity Fig 5. Perceived airway resistance.

of velopharyngeal hypernasality

<25

25-49 airway

as a function

resistance of

deficit

velopharyngeal

perceived by the examiner to have severe hypemasality. These results compare reasonably well with the investigation of Theodoros and coworkers,2 in which 20% of subjects were rated as exhibiting severe hypemasality. The disparity between the studies may be due to very different sample sizes(ie, 20 vs 83). There are some discrepancies between perceived hypemasality and the severity of velopharyngeal airway resistance deficits, possibly because the perception of hypernasality may be influenced by a number of variables, including the patient’s pitch, loudness, voice quality, speaking rate, and intelligibility. Several subjects’ characteristics presented in table 1 may appear incongruous. There are clinical observations that may explain some of the apparent discrepancies. For example, subjects 14, 52, and 58 evidenced very low velopharyngeal airway resistance but were perceived as only mildly to moderately hypemasal. In addition, these subjects were very intelligible. It is likely that the perception of hypemasality was reduced by the fact that their low velopharyngeal airway resistance estimates had a minimal impact on intelligibility. Other disparities are evident in the data for subjects 62 and 63. The judgment of perceived hypemasality was based on conversational interactions throughout the evaluation. In these cases it appeared that /pi/ syllable trains did not reflect their conversational speech. For example, subject 62’s velopharyngeal airway resistance was 100cm HgO/L/sec when producing “puppy.” Subject 63’s velopharyngeal airway resistance was 1OOcm HzO/L/sec in a loud condition, which more closely approximated her conversational speech style. Finally, subjects 40 and 77 evidenced reduced velopharyngeal airway resistance despite no presence of dysarthria. Both of these subjects had a speaking style that could be characterized as “low effort.” Thus, their lower velopharyngeal airway resistance may not have influenced perceived hypemasality because it blended with their overall presentation. It is clear from these data that velopharyngeal airway resistance deficits are common after TBI and evidence an expected correspondence with dysarthria severity. The corre-

VELOPHARYNGEAL

AIRWAY

spondence between velopharyngeal airway resistance deficits and perceived hypernasality is more complex and may be influenced by a number of variables. Continued attention to this contributor to speech production difficulties after TBI is warranted. Acknowledgments: The technical support of John Minton and Lois Patterson is gratefully acknowledged. 1.

2. 3. 4. 5. 6.

References McHenry M, Minton J. The relationship among aerodynamic, acoustic, and perceptual measures of nasality. Paper presented at the meeting of the American Speech-Language and Hearing Association; 1996 Nov 21-24; Seattle, WA. Theodoros D, Murdoch BE, Stokes PD, Chenery HJ. Hypemasality in dysarthric speakers following severe closed head injury: a perceptual and instrumental analysis. Brain Inj 1993;7:59-69. Horii Y. An accelerometric approach to nasality measurement: a preliminary report. Cleft PalateJ 1980;18:279-85. McHenrv M. Wilson R. The challenge of unintelligible soeech following traumatic brain injury. Brainynj 1994;8:36<75. A McHenry MA, Wilson RL, Minton JT. Management of multiple physiologic system deficits following traumatic brain injury. J Med Speech-Lang Path 1994;2:59-74. Workinger MS, Netsell R. Restoration of intelligible speech 13 years post-head injury. Brain Inj 1992;6:183-7.

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Enderby P, Crow E. Long-term recovery patterns of severe dysarthria following head injury. Br J Dis Comm 1990;25:341-54. Yorkston K, Beukelmen D, Traynor D. Computerized assessment of intelligibility of dysarthric speech. Tigard (OR): CC. Publications, Inc.; 1984. Kent RD, Weismer G, Kent JD, Rosenbek JC. Toward phonetic intelligibility testing in dysarthria. J Speech Hear Dis 1989;54: 482-99. Barlow SM, Suing G. Aerospeech: automated digital signal analysis of speech aerodynamics. J Comp Users Speech Hear 1991;7:211-27. Barlow SM, Suing G, Grossman A, Bodmer P, Colbert R. A high-speed data acquisition and protocol control system for vocal tract physiology. J Voice 1989;3:283-93.

Suppliers a. Respironics, 1650 Oakbrook Drive, Suite 480, Norcross, GA 30093. b. Hans Rudolph, Inc., 7200 Wyandotte Street, Kansas City, MO 64114. c. Honeywell, Inc., Honeywell Plaza, Minneapolis, MN 55440. d. Biocommunications, 1918 Browning Road, Madison, WI 53704. e. Computerscope lSC-67, version 3.4, 1985; RC Electronics, Inc., 6464 Hollister Avenue, Golenta, CA 93 117-3 110. f. Aeros version 1.0, 1991; Greg Suing, Boystown National Institute, 555 North 30th Street, Omaha, NE 6813 1.

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