Virginia A. Hinton

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.

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)

Analysis of simulated upper airway breathing.

There is substantial disagreement among clinicians concerning the etiologic significance of impaired nasal respiration. Conflicting views concerning the effects of breathing on facial growth suggest the need for a more quantitative approach to this important question. This investigation is the first in a series of studies representing a new direction for objectively assessing airway breathing. A model of the upper airway was used to study air movement under controlled conditions. The specific objectives were to determine the effects of airway size and shape on the aerodynamics of simulated breathing and develop a theoretical basis for predicting when breathing mode will change from nasal to predominantly oral. The following theoretical predictions are made on the basis of data generated from the model: A nasal airway cross-sectional area of less than 0.4 cm2 may represent an inadequate airway in adults and some mouth breathing would be expected. The amount of adenoid obstruction must be very large to affect airway resistance. However, if airway resistance in the nose is high, large adenoids would present a serious airway problem and cause predominantly mouth breathing. When nasal airway resistance is high, the mouth will open approximately 0.4 to 0.6 cm2. This shifts a significant amount of air orally and reduces airway resistance to a normal level. If morphologic changes are caused by airway impairment, other factors such as a large tongue, large tonsils, or a long, draping velum are probably significant contributing factors.

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.

The relationship between nasal cross-sectional area and nasal air volume in normal and nasally impaired adults.

The controversy concerning the effects of nasal airway impairment on facial growth has stimulated renewed interest in upper airway respiratory function. The subjective manner in which airway impairment and mouth breathing have been assessed is, in our opinion, responsible for the differences observed among investigators and for their conclusions. We have been involved in a series of studies dealing with airway impairment and have report modifications of two techniques for objectively assessing respiration. The purpose of the present study was to examine a large population of adults, with and without nasal airway impairment, and assess the relationship between nasal cross-sectional area and nasal air volume to determine at what point airway size controls the passage of air during breathing. Statistical analysis of the data demonstrates that airway size alters air volume when nasal cross-sectional area is less than 0.4 cm2. The relationship between area and volume is very linear below 0.4 cm2, with air volume decreasing with decreased size. Although the data do indicate some influence over volume at sizes greater than 0.4 cm2, the effect is very slight. These findings support the prediction that upper airway impairment is present at nasal airways less than 0.4 cm2 in adults.

Physiologic responses to maxillary resection and subsequent obturation

Aerodynamic assessment of prosthetic obturation provides the clinician with important information on adequacy of the seal between the oral and nasal cavities. The technique is easy to apply and provides quantitative data on effectiveness of obturation. In addition, the pressure-flow technique provides important information on how individuals respond to changes in the integrity of oral and pharyngeal structures. This study demonstrates that individuals with large surgical defects increase respiratory effort during nonnasal consonant productions in order to maintain adequate intraoral speech pressures. Successful obturation of the defect maintains the speech pressures while dramatically reducing respiratory effort.

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.

Relationships between Integrated Oral-nasal Differential Pressure and Velopharyngeal Closure

Oral-nasal differential pressures are derived measures that incorporate both active (e.g., articulatory) and passive (e.g., nasal structure) components. This study was designed to examine integrated oral-nasal differential pressures in speakers with different levels of velopharyngeal closure. Integrated oral-nasal differential pressure data were obtained from 20 noncleft adults with normal speech and 166 speakers with repaired palatal clefts. Velopharyngeal competency for the cleft subjects, as determined by aerodynamic assessment, ranged from adequate to grossly incompetent. Results of the data analysis indicate that integrated pressures are not maintained at a consistent level across all groups. This lack of consistency across all degrees of velopharyngeal opening may reflect the flexibility, as well as structural limitations, of a speech pressure regulating system.

Age and function differences in shared task performance: walking and talking.

Everyday activity often involves performing two or more simultaneous actions. Common examples are carrying groceries while walking, monitoring traffic while crossing the street, and walking while talking to another person. In older adults, simultaneous performance of two tasks has been shown to lead to performance declines in one or both tasks (Lundin-Olsson, Nyberg, & Gustafson, 1997; Woollacott & Shumway-Cook, 2002). Much of the previous research focused on shared and dual task performance in individuals with cognitive challenges or at risk for falls. Lundin-Olsson and colleagues (1997) found that older adults with a history of falls were unable to carry on a conversation while walking. These individuals tended to stop walking in order to talk with a companion. More recently, Sparrow, Bradshaw, Lamoureux, and Tirosh (2002) determined that increased attentional demands during gait, such as talking, increased reaction time. Increased reaction time during gait may predispose older adults to falls due to a decreased ability to avoid environmental changes, such as circumventing obstacles in their paths. ShumwayCook and colleagues (1997) found that individuals with a history of two or more recent falls swayed more during quiet stance than nonfallers as they completed a series of simultaneous cognitive tasks. Investigating the demands of simultaneous static balance and cognitive tasks has demonstrated the attention-demanding nature of even quiet stance. There have been fewer investigations of shared performance of dynamic tasks; it is equally important to determine the impact of the changing demands of these tasks on older adults. As noted previously, Lundin-Olsson and colleagues (1997) determined that older adults with a history of falls were unable to perform two tasks simultaneously. Many participants in their investigation were cognitively impaired, were depressed, or had had a stroke. Bowen and colleagues (2001) also reported gait changes among older adults recovering from stroke. Velocity decreased and double-support time increased, when these individuals attempted a simultaneous cognitive task. Other investigators have examined dual-task performance in healthy older adults. Chen and colleagues (1996) found that errors increased in both younger and older participants who responded to a visual reaction-time stimulus while walking and attempting to avoid a virtual object. The magnitude of increase was greater for the older adults. Other researchers suggested that a dual task situation requiring memorization also significantly impacts performing a secondary task, including walking over level surfaces. Additionally, there is evidence that cognitive tasks increase alterations in motor performance with increased age (Li, Lindenberger, Freund, & Baltes, 2001; Lindenberger, Marsiske, & Baltes, 2000). Less is known about the effects of normal aging on speech output than other motor actions, because studies of communication integrity have focused on voice production and linguistic parameters rather than speech production characteristics. Studies investigating Age and Function Differences in Shared Task Performance: Walking and Talking

Maintenance of intraoral pressure during speech after maxillary resection

Although structural defects such as cleft palate and severe anterior open bite alter vocal tract resistance, compensatory responses usually result in maintaining consonant pressures at an adequate level. The purpose of the present study was to determine if individuals with an acquired palatal defect spontaneously develop similar compensatory behaviors. The pressure-flow technique was used to measure aerodynamic variables associated with consonant production after surgery and obturation. Although intraoral pressures decreased considerably immediately after surgery, pressures were maintained at a mean level of 3.5-cm H2O. Respiratory volumes increased as much as fourfold without obturation and were normal with obturation. Voice-voiceless differences in air volumes among consonants were maintained even in the presence of the defect. These findings suggest that compensatory responses are directed toward maintaining an appropriate level of intraoral pressure for consonant production.