Pulmonary Blood Flow Model Coupled with Breathing Dynamics.

Abstract

A mathematical model for pulmonary circulation is established taking into account the mechanical behavior coupled with breathing dynamics. The blood flow models in the arterial and venous trees are established by assembling the tube-flow model in each elastic vessel. These models are combined with the sheet-flow model which expresses the blood flow in the capillary network. The finite-element discretization based on adjoint variational principle is applied to solve the model numerically. First, the pulmonary blood flow under a constant gas pressure in the lung is measured using rabbit lungs, and the decrease in blood flow due to gas pressure is observed. The simulation model is verified by comparing the experimental observations with the simulated results, and the causality among the decrease in blood flow, the capillary collapsing and the pressure distribution is discussed. Next, the pulmonary circulation model is coupled with the breathing model to examine the input impedance in normal breathing and to evaluate the effect of varying the inhaled gas pressure in artificial ventilation. It is shown that the results obtained in the simulation correspond to the impedance characteristics observed in experiments in different species. The simulation of artificial ventilation demonstrates that the inhaled gas pressure affects the blood flow not only in arteries and veins but also in the capillaries. These results indicate that the simulation based on the proposed model can be used to investigate the internal mechanical behavior of the pulmonary circulation taking into account the variation due to individuality of the geometry and material properties.