Modelling the ventilation-perfusion mismatch of the cardiopulmonary system in Matlab Simscape

Abstract

A novel model of perfusion distribution in the lung and a novel model of ventilation distribution are developed in this thesis. Both models are focused on the pressure distribution along the thorax due to the gravitation. The lung is divided into three zones: upper zone, middle zone and lower zone. Blood flow increses with the distance from the top of the lung. The upper zone is characterized by a complete collapse of the pulmonary capillary vasculature, thus there is no flow in this zone. The second zone have a “Waterfall effect”, the blood flow is determinated by the difference between the pulmonary artery and alveolar pressures. In the lower zone, the flow is purely driven by the difference between the pulmonary artery pressure and the pulmonary vein pressure. In ventilation, the upper lobe of the lung are more expanded than the middle and lower lobes at resting position. Consequently, ventilation during spontaneous breathing was found nonuniform with more air entering the lower lobes than the middle and upper lobes. As a result, a complete model of perfusion and ventilation in the lung is created and the results obtained in both models are in good agreement with the litetature. Both models are implemented in the object-oriented modeling and simulation module Matlab Simscape.