W. Michael Hairfield

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.

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.

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.

The relationship between nasal airway cross-sectional area and nasal resistance

Mouth breathing in response to an impaired nasal airway is thought to have clinical consequences. Physiologically, mouth breathing occurs whenever the body senses that nasal resistance is inappropriately high. In physical terms mouth breathing is a response that enlarges the upper airway and, by doing so, reduces airway resistance. In the past measurements of nasal resistance have been used as an index of airway impairment. Recently, we introduced a technique that estimates cross-sectional size of the airway, a variable that directly determines the magnitude of airway resistance. The purpose of the present study was to determine the precise effects of nasal airway size on nasal airway resistance so that the relationship between the two could be described in mathematic terms. There were two phases to the study--one involving a model and simulated breathing, and the other involving 100 subjects demonstrating normal and impaired nasal airways. The pressure-flow technique for estimation of nasal airway size and nasal airway resistance was used. The following equation was generated from the data: Resistance = 1.9 + (Formula: see text). The relationship between the two variables is nonlinear--that is, size of the airway has its greatest effect on resistance when the airway is less than 0.4 cm2 and a much lesser effect at larger airway sizes. The study also showed that nasal airway resistance generally does not fall very much below 1.9 cm H2O/L/S during breathing even when the airway is very large. This probably relates to the need to maintain an adequate level of airway resistance for alveolar gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of nasal and oral respiration using inductive plethysmography

The role of nasal respiratory function in oral and facial development remains unclear in spite of the long-standing interest of clinicians. Much of the current controversy stems from our inability to define mouth breathing in objective terms and evaluate nasal airway impairment quantitatively. Recent advances in respiratory monitoring technology provide new opportunities to assess upper airway breathing more objectively. The purpose of this study was to describe a new approach for measuring oral and nasal respiration and to test its reliability. The technique involves inductive plethysmography and the data provide an assessment of respiratory mode without the need to enclose the subjects head in an airtight box. The data were compared to pneumotachography and the results demonstrate the reliability of the technique.

Upper airway pressures during breathing: a comparison of normal and nasally incompetent subjects with modeling studies.

Although there has been considerable interest in the effects of nasal airway impairment on facial growth, the relationship is still unclear. This study examined the effect of nasal airway size on upper airway pressures during breathing. Three phases of data collection were involved. The first phase used a model to describe pressures during simulated normal and impaired respirations. The second phase involved subjects with normal airways, and the third used persons who were judged by an otolaryngologist to be nasally impaired. Aerodynamic assessment techniques were used to measure airway pressures during breathing and to assess nasal airway size. Results of the modeling study suggest that when nasal cross-sectional area is greater than 0.1 cm2, pressures associated with breathing are not excessive. These findings also suggest that slight lip opening (2 to 3 mm) would significantly reduce airway pressures. In addition, pressure magnitudes of the normal and nasally impaired groups were similar to the modeling data, and no significant difference in pressures was observed between the two groups. Accordingly, the assumptions that nasally impaired persons generate abnormal breathing pressures and that these pressures directly influence facial growth are questionable.

The Relationship between Nasal Airway Size and Nasal-Oral Breathing in Cleft Lip and Palate:

Clefts of the lip and palate generally result in reduced size of the nasal airway. Procedures such as the placement of a pharyngeal flap tend to further compromise nasal breathing. The purpose of this study was to determine how size of the nasal airway affects the mode of breathing in adults with cleft lip and/or palate. A heterogeneous population of 50 adult subjects with cleft lip and/or palate was studied. Nineteen of the subjects had pharyngeal flaps. Respiratory inductive plethysmography was used in combination with an integrating pneumotachograph to measure percent nasal breathing. Pressure-flow studies were used to estimate nasal airway size. The data revealed that a majority of subjects had an airway size of less than 0.4 cm2, which constitutes impairment. Mean cross-sectional area for all subjects was 0.38 cm2 +/- 0.20 SD. Seventy percent of the subjects studied were oral breathers to some extent. A Spearman rank correlation coefficient of 0.725 (p less than 0.0001) indicated that oral-nasal breathing mode was related to airway size. Airway size in the subgroup with pharyngeal flaps was even smaller (0.31 cm2), while percent nasal breathing was lower. Mouthbreathing was observed in all subjects whose airway size was less than 0.38 cm2.

The effect of cleft palate speech aid prostheses on the nasopharyngeal airway and breathing

This study determined the effect of a speech aid prosthesis on resting breathing. Nasal cross-sectional area was measured during inspiration and expiration in eight cleft palate patients. The measurements were made for the unobturated defect during both phases of respiration and then repeated while the defect was obturated by a speech aid prosthesis. The results of the study revealed that the presence of a speech aid prosthesis significantly decreased the cross-sectional region of the nasal airway. In 50% of the subjects, the cross-sectional region was less than 0.40 cm2 with concomitant impairment in nasal respiration when the speech aid prosthesis was present in the oral cavity. The data suggest that the design of these prostheses should account for breathing requirements as well as for speech.