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.