David J. Zajac

Assessment of aspiration risk in stroke patients with quantification of voluntary cough

Background: Dysphagia and subsequent aspiration are serious complications of acute stroke that may be related to an impaired cough reflex. It was hypothesized that aspirating stroke patients would have impaired objective measures of voluntary cough as compared with both nonstroke control subjects and nonaspirating stroke patients. Methods: Swallowing was evaluated by standard radiologic or endoscopic methods, and stroke patients were grouped by aspiration severity (severe, n = 11; mild, n = 17; no aspiration, n = 15). Airflow patterns and sound pressure level (SPL) of voluntary cough were measured in stroke patients and in a group of normal control subjects (n = 18). Initial stroke severity was determined retrospectively with the Canadian Neurological Scale. Results: All cough measures were altered in stroke patients as a group relative to nonstroke control subjects. Univariate analysis showed that peak flow of the inspiration phase (770.6 ± 80.6 versus 1,120.1 ± 148.4 mL/s), SPL (90.0 ± 3.1 versus 100.2 ± 1.6 dB), peak flow of the expulsive phase (875.1 ± 122.7 versus 1,884.1 ± 221.6 mL/s), expulsive phase rise time (0.34 ± 0.1 versus 0.09 ± 0.01 s), and cough volume acceleration (5.5 ± 1.3 versus 27.8 ± 3.9 mL/s/s) were significantly impaired in severe aspirators as compared with nonaspirators. Aspirating patients had more severe strokes than nonaspirators (mean Canadian Neurological Scale score 7.7 ± 0.7 versus 9.8 ± 0.3). Multivariate logistic regression found only expulsive phase rise time values during cough correlated with aspiration status. Conclusion: Objective analysis of cough may provide a noninvasive way to identify the aspiration risk of stroke patients.

Age and gender effects on nasal respiratory function in normal subjects.

One hundred and ninety-seven normal individuals between the ages of 5 and 73 years were evaluated to determine nasal resistance, nasal cross-sectional area, and respiratory mode during quiet breathing. Subjects were categorized into three age groups. Nasal resistance and respiratory mode were directly determined using posterior rhinomanometry and the SNORT technique, respectively. Nasal cross-sectional area was estimated using the hydrokinetic equation. Results indicated significant effects of age on all variables; significant gender differences were found for respiratory mode. Weak correlations were found between respiratory mode and nasal resistance. The results are presented as normative data on nasorespiratory characteristics to facilitate diagnostic and treatment decisions relative to individuals with normal morphology as well as to patients with craniofacial anomalies. A fundamental issue of both clinical and theoretical importance arising from the study pertains to the definitions of normality and impairment.

The relationship between spectral characteristics and perceived hypernasality in children

The purpose of this study was to quantify perceived hypernasality in children. One-third octave spectra of the isolated vowel [i] were obtained from 32 children with cleft palate and 5 children without cleft palate. Four experienced listeners rated the severity of hypernasality of the 37 speech samples using a 6-point equal-appearing interval scale. When the average 1/3-octave spectra from the hypernasal group and the normal resonance group were compared, spectral characteristics of hypernasality were identified as increased amplitudes between F1 and F2 and decreased amplitudes in the region of F2. Based on the findings of the childrens speech, 36 speech samples with manipulated spectral characteristics were used to minimize the influences of voice source characteristics on perceived hypernasality. Multiple regression analysis revealed a high correlation (R = 0.84) between the amplitudes of 1/3-octave bands (1 k, 1.6 k, and 2.5 kHz) and the perceptual ratings. Increased amplitudes of bands between F1 and F2 (1 k, 1.6 kHz) and decreased amplitude of the band of F2 (2.5 kHz) was associated with an increasing perceived hypernasality. These results suggest that the amplitudes of the three 1/3-octave bands are appropriate acoustic parameters to quantify hypernasality in the isolated vowel [i].

Direct Measurement of Subglottic Air Pressure While Swallowing

Objective: The subglottic pressure theory for swallowing asserts that laryngeal mechanoreceptors have a role in the regulation of swallowing function. The primary purpose of this study was to determine if subglottic air pressure is generated during swallowing in a healthy, nontracheostomized person.

Evaluating the spectral distinction between sibilant fricatives through a speaker-centered approach

This study was designed to examine the feasibility of using the spectral mean and/or spectral skewness to distinguish between alveolar and palato-alveolar fricatives produced by individual adult speakers of English. Five male and five female speaker participants produced 100 CVC words with an initial consonant /s/ or /ʃ/. The spectral mean and skewness were derived every 10 milliseconds throughout the fricative segments and plotted for all productions. Distinctions were examined for each speaker through visual inspection of these time history plots and statistical comparisons were completed for analysis windows centered 50 ms after the onset of the fricative segment. The results showed significant differences between the alveolar and palato-alveolar fricatives for both the mean and skewness values. However, there was considerable inter-speaker overlap, limiting the utility of the measures to evaluate the adequacy of the phonetic distinction. When the focus shifted to individual speakers rather than average group performance, only the spectral mean distinguished consistently between the two phonetic categories. The robustness of the distinction suggests that intra-speaker overlap in spectral mean between prevocalic /s/ and /ʃ/ targets may be indicative of abnormal fricative production and a useful measure for clinical applications.

Estimation of transpalatal nasalance during production of voiced stop consonants by noncleft speakers using an oral-nasal mask

Objective: Our objective was to estimate nasalance due to transpalatal transfer of acoustic energy during production of voiced stop consonants by noncleft speakers. We also determined the relationship between the transpalatal nasalance and fundamental frequency (F0) of the speakers. Method: Participants were 8 men and 10 women (mean age = 21.9 years, SD = 4.0) without cleft palate who produced voiced stop (/b d g/) and nasal (/m n η/) consonants in syllables embedded in a carrier phrase. Participants also read the Zoo Passage. A divided OroNasal Nasality System mask was used to simultaneously obtain acoustic nasalance and airflow during production of the consonants. Both F0-derived and first formant (F1)–derived nasalance were computed. Results: F0-derived and F1-derived peak nasalance across all speakers ranged from a low of 20% to a high of 80% during production of stop consonants. An estimate of error from the combined sources of transoral transfer of energy (5%) and acoustic crossover between microphones (15%) was no greater than 20%. Analysis of variance revealed no significant effects of the sex of the speakers for either F0-derived or F1-derived nasalance of stops. There was a significant effect of the place of stop production for F0-derived nasalance (p;th< .05). Nonsignificant but positive correlations were found between the F0 of the speakers and F0-derived (r = .25) and F1-derived (r = .45) nasalance. Conclusions: Transpalatal transfer of oral acoustic energy accounts for most nasalance obtained during production of voiced stop consonants by noncleft speakers. F1-derived nasalance appears to better reflect transpalatal effects. Clinical implications are discussed.

Laryngeal airway resistance in children with cleft palate and adequate velopharyngeal function.

Laryngeal airway resistance during vowel production was determined for 10 children without cleft palate and 14 children with cleft palate and adequate velopharyngeal function. The children with cleft palate were further grouped according to either complete or incomplete velopharyngeal closure. All children performed a syllable repetition task with nostrils occluded at self-determined effort and a targeted effort typical of adult speech. Results indicated that all children exhibited significantly greater laryngeal resistance at self-determined effort. No significant differences occurred among the groups of children at either effort level. Some children with incomplete velopharyngeal closure, however, tended to exhibit relatively increased laryngeal resistance at the targeted effort level when their nostrils were unoccluded. Implications for a regulation-control model of speech production and clinical assessment are discussed.

The Effect of Speaking Rate on Velopharyngeal Function in Healthy Speakers

The purpose of this study was to assess the effect of speaking rate variation on aerodynamic and acoustic measures of velopharyngeal (VP) function. Twenty-seven healthy adult speakers (14 males, 13 females) participated in the study. The modified pressure-flow method was used to collect aerodynamic data of /m/ and /p/ segments in the word ‘hamper’ and the utterances ‘Mama made some lemon jam’ (MMJ) and ‘Buy Bobby a puppy’ (BBP). SPL was collected simultaneously with aerodynamic data for all utterances. A Nasometer was used to obtain nasalance scores and nasalance distance for MMJ and BBP. Sentences were produced at normal, fast, slow, and slowest speaking rates. The results showed that nasal airflow and VP orifice area were unaffected by speaking rate variations in males and females, whereas intra-oral pressure appeared to decrease as speaking rate slowed for both speaker groups. However, this effect was removed by statistically controlling SPL. Nasalance and nasalance distance (MMJ – BBP) did not change with speaking rate variation. There was a statistical difference between nasalance scores produced by male and female speakers. The results suggested that aerodynamic and acoustic measures of velopharyngeal function are not affected by variation in speaking rate in healthy males and females.

The Influence of Acoustic and Perceptual Factors on Perceived Hypernasality in the Vowel [i]: A Preliminary Study

The purpose of this study was to examine the influence of acoustic and perceptual factors of speech on listeners’ perceived hypernasality in the vowel [i]. The isolated syllable [pi] produced by 22 children with hypernasal speech and 6 noncleft children was rated by 10 listeners. These speech samples were then divided into two groups: (1) the samples (n = 14) that received inconsistent ratings from each listener or variable ratings among listeners (i.e., unreliable ratings) and (2) the samples (n = 14) that received consistent ratings from each listener and similar ratings among listeners (i.e., reliable ratings). These results suggest that the severity of hypernasality was easy to rate in some speech samples and not in others. Voice quality deviation and a particular type of spectral change that related to the severity of hypernasality could be factors that influence perceived hypernasality.

Reliability and Validity of a Computer-Mediated, Single-Word Intelligibility Test: Preliminary Findings for Children With Repaired Cleft Lip and Palate

Objective To determine the reliability and validity of a computer-mediated, 50-word intelligibility test designed to be a global measure of severity of speech disability in children with repaired cleft lip and palate. Design A prospective between-group design was used with convenience sampling of patients from a university craniofacial center. Participants A total of 38 children between the ages of 4 and 9 years participated. Of these, 22 had repaired cleft lip and palate; whereas, 16 had no clefts. Twenty adults served as listeners. Main outcome Measure(s) Speech intelligibility scores were calculated for repeated administrations of a single-word test based upon the number of correct orthographically transcribed words by four groups of five listeners per child. Measures of parallel forms, interlistener, and intralistener reliabilities were estimated; measures of construct validity were also determined. Results All measures of reliability were adequate. Parallel forms reliability of the test based upon mean scores from five listeners per child was high (r= .97). Thirty-seven of 38 children had differences between forms of 11 percentage points or less. Construct validity of the test was shown by (1) significantly lower speech intelligibility scores for children with cleft lip and palate than controls and (2) a moderately high correlation (r= .79) between intelligibility scores and percent consonants correct for all children. Conclusions A computerized, single-word intelligibility test was described that appears to be a reliable and valid measure of global speech deficits in children with cleft lip and palate. Additional development of the test may further facilitate standardized assessment of children with cleft lip and palate.