Respiratory and laryngeal function associated with experimental coupling of the oral and nasal cavities.

Three experimental openings (10 mm2, 20 mm2, 30 mm2) were placed one at a time in a man's palatal obturator at a location approximating the junction of the prepalate and the palatal shelves. The man's laryngeal and respiratory function were examined during his production of a series of CV syllables [pa] repeated at a comfortable and loud vocal intensity for each of the three experimental conditions. Two more conditions, in which the subject's obturator was not altered (no hole) and in which no obturator was worn, were also included for study. Laryngeal and respiratory function adjustments were most apparent during the 30 mm2 hole size and no obturator conditions. Laryngeal adjustment, as measured by fundamental frequency, was the most identifiable. A respiratory adjustment, which involved the expenditure of more lung volume as nasal airflow leakage increased, was also observed. These observations imply an active physiologic adjustment rather than a passive response to aberrant oronasal coupling.