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 we re used in describing developmental changes in these variables and in hypothesizing corresponding changes in respiratory function. A trend w as found for pressure and resistance to decrease with increases in flo w from preschool age through adulthood. These patterns could be explai ned by the smaller size of laryngeal airway structures and increased e xpiratory muscle forces during speech in the younger subjects. When th e subglottal air pressures were combined with published data on air vo lume expired during speech and recoil pressures of the respiratory sys tem, hypothetical functions were derived for respiratory muscle forces and the work of speech breathing. These functions predict (a) a devel opmental shift from the use of net expiratory muscle force in the spee ch of preschool children to the adult patterns of combined inspiratory and expiratory muscle forces, and (b) the expiratory work of speech b reathing is greater in preschool children than in older children and a dults.