Developmental patterns of laryngeal and respiratory function for speech production.

Estimates of subglottal air pressure, laryngeal airflow, and laryngeal airway resistance from syllable repetitions of children and adults were used in describing developmental changes in these variables and in hypothesizing corresponding changes in respiratory function. A trend was found for pressure and resistance to decrease with increases in flow from preschool age through adulthood. These patterns could be explained by the smaller size of laryngeal airway structures and increased expiratory muscle forces during speech in the younger subjects. When the subglottal air pressures were combined with published data on air volume expired during speech and recoil pressures of the respiratory system, hypothetical functions were derived for respiratory muscle forces and the work of speech breathing. These functions predict (a) a developmental shift from the use of net expiratory muscle force in the speech of preschool children to the adult patterns of combined inspiratory and expiratory muscle forces, and (b) the expiratory work of speech breathing is greater in preschool children than in older children and adults.