Kathleen E. Morr

The relationship between nasal airway size and nasal-oral breathing☆

Most clinicians agree that impaired nasal breathing results in obligatory mouth breathing. Some believe that mouth breathing influences dentofacial growth; others disagree. The term mouth breathing is confusing because total mouth breathing rarely occurs. A combination of nasal and oral breathing is more usual. The purpose of the present study involving 116 adult subjects was to (1) assess the relationship between nasal impairment and nasal-oral breathing, (2) determine the switching range from nasal to nasal-oral breathing, and (3) quantify the term mouth breathing. The pressure-flow technique was used to estimate nasal airway size; inductive plethysmography was used to assess nasal-oral breathing in normal and impaired breathers. Analysis of the date showed a Pearson rank correlation of 0.545 (P less than 0.001) between nasal area and nasal-oral respiration. Ninety-seven percent of subjects with a nasal size less than 0.4 cm2 were mouth breathers to some extent. About 12% of subjects with an adequate airway were assumed to be habitual mouth breathers. The findings indicate that the switching range from nasal to nasal-oral breathing is very narrow (0.4-0.45 cm2). These results also confirm our contention that in adults an airway less than 0.4 cm2 is impaired.

Respiratory response to a decrease in velopharyngeal resistance

Individuals with congenital velopharyngeal impairment generally maintain adequate levels of intraoral pressures during consonant production by increasing respiratory effort. The purpose of the present study was to determine if normal individuals respond to a decrease in velopharyngeal resistance in a similar way. The velar mechanism was perturbed by having subjects voluntarily lower the soft palate during a series of words involving plosive consonants. The pressure-flow technique was used to measure oral pressures, calculate velopharyngeal orifice resistance, and estimate velopharyngeal orifice area. Inductive plethysmography was used to measure breathing volumes associated with the words. The data indicate that, in most instances, intraoral pressure remained at appropriate levels (greater than 3.0 cm H2O) after velar lowering. Speech breathing volume did not change during inspiration, but increased during speech expiration when the velopharyngeal port was open. The difference was statistically significant (p less than 0.01). Duration of the utterance did not change across conditions. A mechanical model was then used to determine how intraoral pressure would be affected by simulating the same conditions in a passive system. The modeling data revealed that pressure would drop threefold. It was concluded that increased respiratory volumes tend to stabilize intraoral pressure when vocal tract resistance is experimentally reduced.

Respiratory response to oral flow and pressure perturbations during speech

Evidence for the regulation/control hypothesis of Warren for speech aeromechanics [Cleft Palate J. 23, 251–260 (1986)] was observed in nine normal men who produced /pʌ/ and /si/ under conditions in which a translabial device released intraoral pressure during /p/, and bite blocks opened the anterior bite artificially during /s/. Intraoral pressures, oral flows, and respiratory volumes associated with utterance were the dependent variables. For /p/, intraoral pressure decreased and translabial air leakage increased as bleed orifice area increased, but mean peak intraoral pressure never fell below 4 cm H2O. For /s/, mean oral flow increased slightly as the anterior bite was opened, but mean peak oral pressure did not vary significantly from control values. Mean flow on the postconsonantal vowels did not vary significantly across the experimental conditions. There were no significant differences among mean inspiratory volumes within or across translabial bleed conditions, nor within or across bite‐Mock condi...

Respiratory response to loss of velar resistance

The hypothesis that speech aerodynamics conforms to the principles of a regulating system was tested in nine normal adult subjects. The velar mechanism was perturbed by having subjects lower the soft palate during a series of words involving plosive consonants. The pressure‐flow technique was used to measure oral pressures and velar resistance. Inductive plethysmography was used to measure tidal volumes associated with test consonants. The data indicate that intraoral pressure remained at appropriate levels (> 4.0 cm H2O) after loss of velar resistance. Tidal volume did not change during inspiration but increased during speech expiration. The difference was statistically significant (p < 0.01). These results support previous findings of Warren [Cleft Palate J. 23, 251–260 (1986)] in cleft subjects, Putnam et al. [J. Speech Hear. Res. 29, 37–49 (1986)] in perturbation studies, and Warren et al. [J. Acoust. Soc. Am. 67, 1828–1831 (1980), Folia Phoniatr. 33, 380–393 (1981), Folia Phoniatr. 36, 164–173 (1984)...