Oronasal fistulas, intraoral air pressure, and nasal air flow during speech.

Aeromechanical data are presented for six patients with oronasal fistulas and one with a maxillary cleft. Patients were studied with the defects open and again with them closed with either acrylic dental appliances, dental wax, or denture adhesive. Only the largest openings appeared to allow sufficient loss of intraoral air pressure to weaken obstruent consonants. All but the smallest of the defects were associated with nasal air flow during syllable strings. Thus the data are compatible with a hypothesis that in the presence of small air leaks patients maintain sufficient intraoral air pressure for accurate consonant production. Presumably this is achieved by increase in respiratory effort. The relationship between fistula size and speech or speech related variables appears to be similar to that between area of the velopharyngeal opening and speech. However, the fistula is more constant in area across utterances than is the pathological velopharyngeal mechanism.