Aerodynamic assessment of velopharyngeal function in speech

Abstract

Velopharyngeal function in speech was assessed by aerodynamic techniques, which were developed and tested. Temporal and dynamic characteristics of the nasal airflow pattern during the velopharyngeal closing phase in speech were studied in different patient groups. Its validity in relation to listener's perceptual evaluation of speech was analyzed.Temporal and dynamic measures of the nasal airflow declination during the transition from nasal (velopharynx open) to stop (velopharynx closed) consonants in speech were analyzed in 19 children with and 22 without cleft palate. In 11 normal speakers the oropharyngeal and nasal pressure, nasal airflow, and the corresponding velopharyngeal opening area was estimated. The speech sample included sentences containing nasal-to-stop combinations in bilabial, dental, and velar places. For validation, the nasal airflow measures were compared to perceptual ratings of velopharyngeal function and hypernasality. In children with cleft palate the duration of nasal airflow declination was longer (p < .0001), the maximum flow declination rate slower (p <.006) and the nasal airflow during stop consonants higher (p <.004) than in controls. Both the sensitivity and specificity were 1.00 for the temporal airflow measure in the bilabial nasal-to-stop consonant combination /mp/ in relation to perceptual ratings of 'velopharyngeal function'. Aerodynamic differences between articulation positions were noted both among normal speaking adults and children with and without cleft palate. In 26 adult males with sleep disordered breathing (SDB) and 11 non-snoring, male controls, no major differences were found with regard to the nasal airflow pattern during speech. However, subjects with more severe sleep apnea and/or high body mass index had somewhat slower maximum speed of airflow declination. In conclusion, assessment of the temporal and dynamic characteristics of the nasal airflow variations during the velopharyngeal closing phase in speech appears useful for evaluation of velopharyngeal function. The method seems to distinguish between perceptually normal and deviant velopharyngeal function with high sensitivity and specificity in children with and without cleft palate. The data suggest that the maximum speed of velopharyngeal closure may be affected in some individuals with SDB. The place of articulation should be taken into consideration for aerodynamic assessment of velopharyngeal function in speech.