Abstract
An extended model is proposed for lung respiration. This model is made to cope with gas diffusion by convection in the airway network, gas exchange at the alveolus, gas transport by blood flow, and gas flow in the airway network induced by diaphragm motion. The submodel for each phenomenon is combined into a total respiratory system, and it is formulated in the context of discretization based on the adjoint variational principle. First, the normal respiration and then the high-frequency ventilation (HFV) are studied by means of this model. The effects of HFV are evaluated through several case studies and it is quantitatively shown that the influence of the convective diffusion is dominant in the gas transport of HFV. The proposed model is expected to be used to determine proper parameters of HFV.
