Modeled velocity of airflow in the airways during various respiratory patterns.

Our modeling and simulation of the respiratory system with Weibel's morphometry shows that the average velocity of expiratory airflow is always greater than the average velocity of inspiratory airflow during tidal breathing when the intervals of inspiration and expiration are same. A nonlinear circuit model was developed comprised with the upper airway, the conducting airways (trachea approximately terminal bronchioles), and the lumped alveolar space. These compartments are established with known physiologic pulmonary characteristics that are represented by nonlinear resistors and capacitors. In this paper we set up the circuit model reflecting the geometric variation of airways during tidal breathing, and demonstrated computation results for the velocity of airflow along the airways based on 16 different respiratory patterns. The circuit model offers a convenient method that can be used to investigate the velocity of airflow and its interaction with mucus, as well as suggests a basic model for our future research on analyzing airway clearance techniques.