Influence of airway wall properties on respiratory system response characteristics

Abstract

Changes of airway wall physical properties are associated with inflammation and swelling of the airway passages. This contributes to airway obstruction and increased work of breathing. A model is developed to study the effect of changes in the wall properties on the dynamic characteristics of the respiratory system. Both symmetric and asymmetric structures are considered. By developing some insight into the correlation between the respiratory system structure and its acoustical response, groundwork is set for the analytical interpretation of high frequency response data in clinical and laboratory tests. The response of the lung structure indicates that when the airway wall elastance and inertance are varied, as the case during asthma attack (airway walls get swollen results in airway constriction and tissue properties changing), the overall normalized input impedance frequency spectrum measured at the throat gives a reasonable signature for identifying such abnormality. The identification procedure is based on comparing the frequency spectrums of healthy and unhealthy lungs. The branching structure of the airway walls and its dynamical properties appear to significantly influence the lung response.