Interaction model between circulatory and respiratory system

The present study was prepared in order to illustrate the gas exchange (02 and C02) between pulmonary blood and alveolar air. In the model, circulatory and respiratory systems have been separately simulated in order to obtain the driving functions of the interaction model. This last takes into account oxygen and carbon dioxide exchanges between alveolar air and pulmonary blood. The circulation model is simulated by an RLC network which has proper auto- and mutual admittances. Cardiac pressures have been considered as driving functions and arterial and venous blood flows are so obtained. The respiratory model is simulated by a block, with proper resistance and compliance with respiratory muscle effort as a driving force and tidal volume as output function. The significant variables of the interaction model are alveolar air and pulmonary blood concentrations of 02 and C02. These are determined from blood flows and tidal volume previously obtained and from gas diffusion across the alveolar membrane. The capillary bed is divided into a discrete number of cells and time in finite intervals and then the diffusion law is solved with a finite difference method. The particular interest of the method is in the step-by-step procedure which allows us to obtain a complex model from the combination of simpler models. Copyright © 1972 by The Institute of Electrical and Electronics Engineers, Inc.