Donald W. Warren

Changes in nasal airway resistance associated with rapid maxillary expansion

Records consisting of nasal resistance measurements, postero-anterior radiographs, and dental casts were obtained on seventeen patients before they underwent rapid maxillary expansion. These records were retaken after maximum expansion of the appliance and after 3 months of retention. Measurements of nasal resistance, binasal cavity width, and maxillary first molar width were made for each subject at each stage of treatment. The following conclusions were derived: 1. Rapid maxillary expansion produced a significant reduction in nasal resistance measured at both 0.50 L. per second and 0.25 L. per second air flow. The reduction of nasal resistance by maxillary expansion was stable through a 3-month period of retention. 2. There was very low correlation between the amount of maxillary first molar expansion and change in nasal resistance. Also, changes in nasal resistance showed low correlation with the amount of nasal cavity widening which occurred during the expansion procedure. 3. Changes in nasal cavity width was not closely related to the amount of maxillary first molar expansion. 4. The patients subjective opinion of changes in his ability to breathe through the nose was not closely related to the amount his nasal resistance was reduced. 5. The change in nasal resistance of subjects who noticed an improvement in their ability to breathe through the nose was not significantly different from nasal resistance change in children who did not notice any change in their breathing. 6. When subjects treated with an all-wire expansion appliance were compared to subjects treated with a wire-and-acrylic appliance, the two groups were not significantly different with respect to maxillary first molar expansion, nasal cavity widening, or changes in nasal resistance. Differences in amount of molar tipping or alveolar bending were not investigated. 7. Patients requiring rapid maxillary expansion treatment for constricted maxillary arches have significantly higher nasal resistance than other orthodontic patients and nonorthodontic subjects. The rapid maxillary expansion procedure reduced the nasal resistance of those treated to a level which was not significantly different from that of subjects with maxillary arches of normal dimensions. 8. The reduction in nasal resistance achieved with the expansion procedure was not lost after 3 months of retention. 9. Where indicated, rapid maxillary expansion is not only an effective method for increasing the width of narrow maxillary arches but also reduces nasal resistance from levels associated with mouth breathing to levels compatible with normal nasal respiration.

The nasal airway following maxillary expansion

There have been suggestions that maxillary expansion may be justified on the basis of airway considerations alone. The present study assessed the effects of rapid maxillary expansion and surgical expansion on nasal airway size to determine how useful these techniques are for breathing purposes. The results demonstrate that both procedures generally improve the nasal airway. However, approximately one third of the subjects in both groups did not achieve enough improvement to eliminate the probability of obligatory mouth breathing. These findings suggest that maxillary expansion for airway purposes alone is not justified.

Quantitative evaluation of nasal airflow in relation to facial morphology

This study examines the relationship between facial morphology and nasal respiration. Nasal resistance to expiratory airflow, average volume flow rate, and temporal characteristics of the respiratory cycle were measured for twenty-eight adults. Subjects were categorized as having (1) normal facial proportions with competent lips (n = 10), (2) normal facial proportions with incompetent lips (n = 9), and (3) long vertical face height (n = 9). Results indicate that the three groups do not differ significantly in terms of nasal airflow. Lip incompetence is not synonymous with mouth breathing. Although long-faced subjects as a group had a higher mean value of nasal resistance, the range of variation was so great as to preclude the diagnosis of nasal obstruction from an assessment of facial morphology.

Relationship between vertical dentofacial morphology and respiration in adolescents

The relationship between vertical dentofacial morphology and respiration has been debated and investigated from various approaches. The purpose of this study was to use contemporary respirometric techniques to compare the breathing behavior of normal and long-faced adolescents. Sixteen normal and 32 long-faced subjects 11 to 17 years of age were chosen clinically and verified by means of a discriminant function. Vertical and anteroposterior facial form was assessed from lateral cephalometric radiographs according to the following measurement criteria: six skeletal angular, eight skeletal linear, four dental linear, and three skeletal ratios. Breathing behavior was quantified according to tidal volume, minimum cross-sectional nasal area, and percent of nasal breathing as assessed by pneumotachography, measurement of differential pressures, and inductive plethysmography. The data indicated that the normal and long-faced groups were significantly different with respect to lower face form, and each group in the study was comparable to groups that had been chosen by previous investigators. Multiple regression analysis demonstrated that the normal and long-faced groups had similar tidal volumes and minimum nasal cross-sectional areas, but the long-faced subjects had significantly smaller components of nasal respiration. These results illustrate that groups without significant differences in airway impairment can have significantly different breathing modes that may be behaviorally based, rather than airway-dependent.

Nasal resistance, skeletal classification, and mouth breathing in orthodontic patients

1. 1. A subjective classification of the breathing pattern of each of fifty-one patients presenting for orthodontic treatment reveals that thirty-one were nasal breathers and twenty were mouth breathers. 2. 2. The skeletal classification by the AB difference method was considered to be reliable in this study. 3. 3. The magnitude of nasal resistance and the subjects skeletal classification were found to be independent of each other. 4. 4. The breathing pattern and the skeletal classification of the subject were also found to be independent of each other. 5. 5. In the thirteen subjects with nasal resistance above 4.5 cm. H2O/liter/second, a deviation of the nasal septum was noted in six, injection of the turbinates in two, and allergic rhinitis in two. Three subjects were considered within normal limits. 6. 6. The incidence of clinically observable mouth breathing was found to be greater among the subjects with a nasal resistance above 4.5 cm. H2O/liter/second (77 per cent) than among those with a nasal resistance below this value (26 per cent).

A quantitative technique for assessing nasal airway impairment

The controversy concerning the effects of impaired nasal respiration on dentofacial development stems largely from the lack of a reliable method to assess airway impairment. The purpose of this study was to develop and validate a quantitative technique to estimate nasal airway dimensions so that normal and impaired nasorespiratory function could be defined. The method involves a modification of the theoretical hydraulic principle and utilizes the following equation to estimate cross-sectional area of the nose (NA): NA = V/K [2(delta P)/d] 1/2 (where d = density of air). Pressure drop (delta P) across the nose is measured simultaneously with airflow (V) through the nose during breathing, using appropriate transducers and a PDP 11/34 computer. An analog model of the upper airway was used to determine the discharge coefficient (k) and estimate measurement error. Model studies demonstrate a measurement error of less than 5% for nasal cross-sectional areas of 0.02 to 1.2 cm2. Studies involving eighteen adult subjects and twenty-six children 8 to 11 years of age revealed mean smallest cross-sectional nasal areas of 0.62 cm2 +/- 0.17 and 0.43 cm2 +/- 0.076, respectively. The results indicate that the technique should enable clinicians to (1) estimate size of the airway during breathing, (2) distinguish between normal and impaired nasal respiratory function, and (3) determine quantitatively the effects of surgical and/or orthodontic treatment for improving nasal respiration.

Alterations in nasal airway resistance following superior repositioning of the maxilla

Superior repositioning of the maxilla is a contemporary surgical procedure used to correct a variety of dentofacial deformities, including vertical maxillary excess. Concern for the effect of this procedure on nasal respiration is warranted, since superior repositioning of the maxilla may decrease the volume of the nasal cavity. In this study pre- and postoperative nasal-resistance values were obtained for 52 patients who underwent superior repositioning of the maxilla by the LeFort I downfracture procedure. Of these 52 patients, 24 underwent segmental osteotomies and 28 underwent one-piece superior repositioning. Results indicate that the long-faced persons for whom superior repositioning of the maxilla is recommended usually have pretreatment nasal-resistance values within previously reported normal ranges. Superior repositioning of the maxilla, with or without involvement of the nasal floor, usually results in decreased nasal resistance.

Hypernasality and Velopharyngeal Impairment

Although the primary cause of hypernasality is impaired velopharyngeal (VP) function, a variety of other factors influence the outcome perceived by the listener. The purpose of the current study was to assess the relationship between oral-nasal resonance balance and (1) velopharyngeal orifice area; (2) nasal airflow rate; and (3) duration of nasal airflow. The pressure-flow technique was used to estimate VP area and measure nasal airflow rate and duration. Ratings of oral-nasal balance were made on a 6-point equal-appearing interval scale. Results indicated a moderate correlation between hypernasality rating and VP area (0.66), nasal airflow (0.61), and nasal airflow duration (0.53). Adults tended to be perceived as more hypernasal than children for a given degree of VP impairment. Finally, when the degree of VP opening was small, perceived oral-nasal resonance balance appeared to be related to duration of the opening-closing movements.

Effect of age on nasal cross-sectional area and respiratory mode in children

Although nasal cross‐sectional size has been reported for adults, no information is available concerning the effects of age on nasal area and breathing mode in children. Determination of the effect of age on nasal size is necessary in order to define nasal airway impairment in children. The purpose of this study was to determine mean nasal cross‐sectional size in children between the ages of 6 and 15 years. One hundred two children were assessed during resting breathing. The pressure‐flow technique was used to estimate nasal cross‐sectional size, and inductive plethys‐mography was used to assess nasal‐oral breathing. The results indicate that nasal airway size increased approximately 0.032 cm2 each year. Mean nasal cross‐sectional area increased from 0.21 ± 0.05 cm2 at age 6 to 0.46 ± 0.15 cm2 at age 14. The percentage of nasal breathing also increased with age.

Nasalance and nasal area values: cross-racial study.

Nasometry and nasal cross-sectional area data were obtained from 80 normal male and female speakers (40 African-Americans and 40 white Americans) all of whom were over the age of 18 and spoke the Mid-Atlantic dialect of American English. The nasalance scores for readings of the Zoo Passage did not differ significantly between the groups. However, nasalance scores for readings of the Nasal Sentences were found to be significantly higher among the white speakers. The pressure-flow method was used to obtain nasal cross-sectional area values. There were no racial differences in nasal cross-sectional area. The Nasal Sentences scores were not highly correlated with nasal cross-sectional area. The clinical significance of these findings is discussed.