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Biomedical subjects

R M Dalston

Publications and source records attributed to R M Dalston.

At least 37 records · Page 2Linked to original sources
PubMed1991

Use of nasometry as a diagnostic tool for identifying patients with velopharyngeal impairment.

A series of 117 patients were studied in an attempt to determine the extent to which acoustic assessments of speech made with a Kay Elemetrics Nasometer corresponded with aerodynamic estimates of velopharyngeal area and clinical judgments of hypernasality. Nasometer data were obtained while patients read or repeated a standardized passage with no nasal consonants. Pressure-flow data were obtained from 96 of these patients during repeated productions of the word "papa." Listener judgments were made in a clinical setting by the senior author using a 6-point equal-appearing interval scale. Nasometer and pressure-flow results were not known to the senior author when making listener assessments. With a cutoff nasalance score of 32, the sensitivity of Nasometer ratings in correctly identifying the presence or absence of velopharyngeal areas in excess of 0.10 cm2 was 0.78 and 0.79, respectively. The sensitivity and specificity of nasometry in correctly identifying subjects with more than mild hypernasality in their speech was 0.89 while the specificity was 0.95. The results suggest that the Nasometer is an appropriate instrument that can be of value in assessing patients suspected of having velopharyngeal impairment.

Acoustics↗
PubMed1991

Increased nasal resistance induced by the pressure-flow technique and its effect on pressure and airflow during speech.

Although the validity of the pressure-flow technique has been verified in a number of laboratories, some questions still remain. The purpose of this study was to determine whether the procedures involved in estimating orifice size affect the pressure and airflow variables being measured. Twenty subjects with demonstrated velopharyngeal inadequacy on pressure-flow testing (VPO greater than or equal to 0.10 cm2) were assessed under two contrasting conditions. Subjects were asked to produce (p) in the word "hamper" with a) one nostril occluded by a cork as in pressure-flow testing and b) both nostrils patent. The results indicate that the increased nasal resistance resulting from occlusion of one nostril does not appreciably affect pressure and airflow associated with plosive consonant production in patients with velopharyngeal inadequacy.

Adolescent↗
PubMed1990

The modified tongue-anchor technique as a screening test for velopharyngeal inadequacy: a reassessment.

Pressure-flow assessment of velopharyngeal (v-p) orifice size was used to test the accuracy with which tongue-anchor task results categorize patients differing in v-p adequacy status. The results indicate that this screening task was fairly accurate in identifying patients with v-p adequacy as defined by aerodynamic assessment (specificity = 0.85). It was not quite as accurate in correctly categorizing patients with inadequacy (sensitivity = 0.78). The predictive power of this screening test and its utility in a school setting are discussed.

Adolescent↗
PubMed1990

Using simultaneous nasometry and standard audio recordings to detect the acoustic onsets and offsets of speech.

Simultaneously collected nasometric and standard audio recording data were compared to determine the extent to which the acoustic onsets and offsets of speech could be determined from Nasometric signals. Three male and 2 female subjects produced six repetitions of 12 utterances that were initiated and terminated by vowels and consonants of differing phonetic features. The onset of Nasometer output typically followed output from the standard audio recording system by an average of 29 ms (SD = 36.1 ms). A greater temporal discrepancy was observed for signal offsets (mean Nasometer lag = 100 ms; SD = 83.3 ms). Large differences between the two instruments seemed due to differences in their overall sensitivities. The results suggest that the Nasometer may be of limited value in determining the acoustic onsets and offsets of speech. The Nasometer was not designed to sense the acoustic events studied here, and the current results have no bearing whatsoever on the validity of this instrument in providing information concerning nasal resonance.

Adult↗
PubMed1990

Maintaining speech pressures in the presence of velopharyngeal impairment.

Most, but not all, individuals with velopharyngeal inadequacy maintain consonant pressures greater than 3 cm H2O even with decreased velar resistance. The purpose of this study was to identify variables that might differentiate those who achieve adequate pressures from those who do not. Forty-four cleft lip and/or palate subjects were assessed during production of /p/ in the word "hamper." Twenty-three subjects achieved pressures greater than 3 cm H2O and 21 did not. The pressure-flow technique was used to assess velopharyngeal orifice size, nasal resistance, velar resistance, and nasal airflow during speech. Nasal cross-sectional area was measured during breathing. The data were analyzed by age and gender. Results indicate that the inability to achieve adequate consonant pressures in the presence of velopharyngeal inadequacy is more likely to occur in adults than in children. Although children are known to produce consonants at higher pressures than adults, the age disparity between groups did not account for the pressure differences. The most significant factor differentiating adequate and low pressure speakers was the magnitude of nasal plus velar resistance. This difference was consistent across age and gender.

Adolescent↗
PubMed1990

Nasometric and phototransductive measurements of reaction times among normal adult speakers.

The temporal relationship among laryngeal, velopharyngeal, and labial activity was investigated by studying the reaction times of eight normal adults. Four female and four male subjects sustained production of the nasal consonant /m/ until a computer-driven imperative tone was presented at which time they were required to say /pi/ as quickly as possible. This task was repeated 30 times for each subject. The offset of voicing at the end of the /m/ and the onset of bilabial plosive release were monitored using a commercially available Nasometer. The onset of velopharyngeal (V-P) movement toward closure and the attainment of closure were monitored using a photodetector system. Across 240 responses, the average latencies were: 146 ms for initiation of V-P movement toward closure, 224 ms for voicing offset, 280 ms for onset of V-P closure and 317 ms for onset of plosive release. The significance of these findings is discussed with respect to speech motor control and the clinical evaluation of patients with velopharyngeal impairments.

Acoustics↗
PubMed1990

The aerodynamic characteristics of speech produced by normal speakers and cleft palate speakers with adequate velopharyngeal function.

Pressure-flow data were obtained on 20 noncleft adults with normal speech and 26 adults with repaired cleft palate. All subjects had adequate velopharyngeal function as determined by preliminary aerodynamic assessment. Subjects were considered to have adequate closure if they had velopharyngeal areas no greater than 0.049 cm2 during production of /p/ in the word "hamper." Although the subjects in both groups demonstrated velopharyngeal adequacy, the subjects with cleft palate produced speech with significantly less nasal airflow. In addition, their intra-oral pressure curve was shifted forward in time. These differences suggest that speakers with cleft palate and adequate velopharyngeal function make certain compensatory adjustments that may be necessary because of differences in velopharyngeal movement capabilities. The potential significance of this for treatment planning is discussed.

Adolescent↗
PubMed1989

Using simultaneous photodetection and nasometry to monitor velopharyngeal behavior during speech.

The purposes of this investigation were (a) to study the temporal relationships among velopharyngeal closing and opening maneuvers monitored by phototransduction and the onset and offset of Nasometer output signals and (b) to determine the extent to which photodetector output maxima are correlated with output peaks from the Nasometer when both are used simultaneously to monitor nasal productions among normal speakers. Simultaneous Nasometer and photodetector data were collected from 6 normal adult subjects as they produced 6 repetitions of 10 sentences. A major finding of this study was that over 96% of the 540 nasal utterances studied produced Nasometer and photodetector signal maxima that were within 30 ms of one another. The results of this study also suggest that simultaneous nasometry and photodetection may provide useful information concerning the temporal relationships among various velopharyngeal movements and the onset and offset of speech as indicated by output signals from the Nasometer. The potential use of this procedure with clinical patients is discussed.

Adult↗
PubMed1989

An analysis of velopharyngeal timing in normal adult speakers using a microcomputer based photodetector system.

Using a microcomputer interface and dedicated software, a photodetector was employed to collect data on the timing of velopharnygeal movements during the production of speech by 10 normally speaking adult subjects. The duration of velopharnygeal closing gestures varied consistently across productions of /m/, /n/ and /n/ in both normal and fast speech. Velopharyngeal opening movements also appeared to be affected by the nasal consonant that was produced. These phenomena are explained in terms of biomechanical constraints known to act upon the velopharyngeal mechanism.

Adult↗
PubMed1989

Effects of velar resistance on speech aerodynamics.

The level of intelligibility attained by speakers with cleft palate reflects not only the ability to achieve adequate velopharyngeal closure but other complex variables as well. When closure is inadequate, performance is influenced by compensatory responses of the tongue, vocal folds, respiratory muscles and nasal valve. The purpose of the present study was to determine how a loss of velar resistance associated with velopharyngeal inadequacy affects speech pressures and airflow. The pressure-flow technique (Warren, 1979) was used to assess mean airflow rate, mean intraoral and nasal pressures and velopharyngeal orifice areas in 211 subjects diagnosed as having cleft palate or velopharyngeal inadequacy. The data revealed that resistance fell as velopharyngeal orifice area increased. Intraoral pressures also fell as resistance dropped while nasal pressures and airflow rate increased. These findings suggest that individuals with velar inadequacy and associated low velar resistance compensate by increasing airflow rate in an attempt to maintain adequate pressures for consonant sound production.

Adolescent↗
PubMed1989

Respiratory response to a decrease in velopharyngeal resistance.

Individuals with congenital velopharyngeal impairment generally maintain adequate levels of intraoral pressures during consonant production by increasing respiratory effort. The purpose of the present study was to determine if normal individuals respond to a decrease in velopharyngeal resistance in a similar way. The velar mechanism was perturbed by having subjects voluntarily lower the soft palate during a series of words involving plosive consonants. The pressure-flow technique was used to measure oral pressures, calculate velopharyngeal orifice resistance, and estimate velopharyngeal orifice area. Inductive plethysmography was used to measure breathing volumes associated with the words. The data indicate that, in most instances, intraoral pressure remained at appropriate levels (greater than 3.0 cm H2O) after velar lowering. Speech breathing volume did not change during inspiration, but increased during speech expiration when the velopharyngeal port was open. The difference was statistically significant (p less than 0.01). Duration of the utterance did not change across conditions. A mechanical model was then used to determine how intraoral pressure would be affected by simulating the same conditions in a passive system. The modeling data revealed that pressure would drop threefold. It was concluded that increased respiratory volumes tend to stabilize intraoral pressure when vocal tract resistance is experimentally reduced.

Humans↗
PubMed1989

The speech regulating system: temporal and aerodynamic responses to velopharyngeal inadequacy.

Temporal and respiratory responses to a loss of velar resistance were measured in 107 subjects demonstrating varying degrees of velopharyngeal inadequacy. The subject data were compared to data generated by a mechanical model representing a passive system. The pressure-flow technique was used to estimate velopharyngeal orifice size and measure respiratory and temporal characteristics of aerodynamic events associated with the production of the nasal-plosive blend /mp/ in the word "hamper". Subjects were categorized as having adequate closure (less than 0.05 cm2), adequate/borderline closure (0.05-0.09 cm2), borderline/inadequate closure (0.10-0.19 cm2) and inadequate closure (greater than or equal to 0.20 cm2). The data revealed that intraoral pressure fell 10-fold in the model as velopharyngeal orifice area changed from adequate closure to inadequate. The subject data demonstrated only a 1.4-fold drop in pressure. Airflow data indicated that there was a 10-fold increase in respiratory volume in the subject data corresponding to the change from adequacy to inadequacy. When respiratory and temporal responses were assessed together, the findings revealed that airflow and temporal changes minimized the fall of pressure as velar resistance declined across groups.

Adolescent↗
PubMed1989

Screening of velopharyngeal inadequacy by differential pressure measurements.

Warren (1979) described an approach for screening velopharyngeal inadequacy using a device (PERCI) that measures orifice differential pressure (P). The PERCI score is based on the relationship between velopharyngeal orifice (VPO) area and velopharyngeal orifice differential pressure. The purpose of this study was to test the original assumptions, which were based on modeling experiments and a small sample size. The sample in this study included 515 subjects who demonstrated various degrees of velopharyngeal inadequacy. The pressure-flow technique was used to estimate velopharyngeal orifice size and to measure orifice differential pressure. The data demonstrate that differential pressures greater than 3.0 cm H2O generally predict adequacy of closure, whereas differential pressures less than 3.0 cm H2O usually indicate inadequacy. These findings support the use of orifice differential pressure as a simple screening of velopharyngeal function.

Humans↗
PubMed1988

Intraoral pressure, nasal pressure and airflow rate in cleft palate speech.

We have suggested that compensatory behaviors associated with cleft palate may be strategies developed for the purpose of satisfying the requirements of a speech regulating system. The purpose of the present study was to test this hypothesis in subjects demonstrating various degrees of velopharyngeal inadequancy. The pressure-flow technique was used to assess aerodynamic responses to a loss of velar resistance in 74 subjects compared to a control group of 137 subjects with adequate velopharyngeal closure. The results of this study demonstrate that as degree of inadequacy increased, airflow rate also increased. Although intraoral pressure fell as inadequacy increased, many subjects were able to maintain pressures above 3.0 cm H2O by increasing airflow rate. Nasal pressure increased in proportion to the decrease in intraoral pressure while combined nasal plus oral pressure remained constant across groups. These findings suggest that a loss of resistance at the velar port is compensated by an increase in resistance at the nasal port. Airflow rate appears to be adjusted to total upper airway resistance. These findings support our contention that the speech system is constrained to meet aerodynamic requirements.

Adolescent↗
PubMed1988

A comparison of photodetector and endoscopic evaluations of velopharyngeal function.

Simultaneous videoendoscopic and photodetection analyses were made of specific onset and offset times of velopharyngeal opening and closing in two normal speaking subjects. Both procedures were found to have acceptable measurement repeatability and to agree with each other when used to determine movement changes. It is felt that when used together, these techniques contribute to improved understanding of velopharyngeal activity during speech.

Endoscopy↗
PubMed1988

Digital, labial, and velopharyngeal reaction times in normal speakers.

The relationship between inherent speed limitations of the velopharyngeal mechanism and the observed phenomenon of assimilation nasality was investigated by studying the reaction times of 10 normal adults performing three movements: (1) lip closing, (2) velopharyngeal closing, and (3) pressing a response key with a finger. The first two movements were monitored using a photodetector system. Across nearly 300 responses for each of the motor responses, the average reaction times, in milliseconds, were 194 for the digital, 203 for the labial, and 206 for the velopharyngeal movements. An analysis of variance revealed no consistent differences among these responses. The significance of these data is discussed with respect to speech motor control and clinical evaluation of patients with velopharyngeal impairments.

Adult↗
PubMed1988

Intraoral pressure and its relationship to velopharyngeal inadequacy.

Intraoral pressure measurements were made during multiple productions of the word "hamper" by each of 267 patients who manifested differing degrees of velopharyngeal inadequacy. The results indicate that intraoral pressure diminishes as the extent of velopharyngeal impairment increases. However, pressure remained above 3 cm H2O in the majority of subjects, even when the impairment was such that intraoral and intranasal pressures were essentially equal. Comparison of these results with model simulations suggests that speakers make adjustments to velopharyngeal impairment that tend to maintain pressures at levels thought to be necessary for obstruent consonant production. Variations in pressure as a function of gender and age parallel those observed in normal children and adults.

Adolescent↗