Clefts of the lip and palate frequently produce nasal deformities that affect airway patency and breathing behaviors. Surgical procedures that correct nasal asymmetry or palatal inadequacy may further compromise the airway. Previous longitudinal studies of nasal airway patency and breathing mode have been limited to those over 6 years of age because subject participation is required for reliable rhinomanometric measurements. Thus, there are no data on neonates and very young children despite the fact that several surgical procedures are performed during this critical period. A new technology, Acoustic Rhinometry, will be used to assess the effects of early growth and surgical intervention in young children. This new approach will close a significant gap in our present database and provide clinically relevant information on airway compromise and breathing behaviors in this special population. A second line of study concerns breathing as a regulating system phenomenon. Specifically, aerodynamic and psychophysical techniques will be used to assess how subjects respond physiologically and behaviorally to sudden, imposed changes in the breathing environment. The primary aim is to characterize basic properties of the sensory system used to monitor breathing and determine how clefting and nasal airway impairment affect the homeostatic monitoring system. The specific questions to be addressed are: l)What minimum change in resistance load is perceived during breathing? 2)How great are the sensitivity and responsivity of the aerodynamic monitoring system to a sudden change in resistance load? 3)Does the psychophysical threshold vary with the duration of the applied loads? 4)How are the sensitivity of the respiratory monitoring system and the latency of a physiologic response affected by change in duration of load application? 5)Are there physiologic adjustments that occur in response to applied loads that are not perceived? 6)Does age affect the perception of, or physiologic adjustments to, resistance loads? A third line of study provides additional information on the neural processing mechanisms involved in monitoring breathing. One experiment alters airflow receptors and the other examines cortically recorded evoked potentials under changing airway environments. Information obtained from these experiments will serve as a test of the regulating system hypothesis.
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