Computer simulation of respiratory control system

The respiratory system in a human body is a control system for maintaining the stability of the body against the variations of the external environment. In the system, the gas concentration in the alveoli and the blood play an important role as a source of information. A computer simulation of the respiratory system is performed based on a model in which the diffusion phenomenon and the gas transportation delay are incorporated. Also, analyses of the response of the system to a variation of the control mechanism as well as of the overall inspired gas components in the system are conducted. The simulation model used in this paper is largely composed of two components, i.e., the control system itself and several kinds of body tissues, representing a whole body. The system to be controlled is the vascular circulatory system which connects the lungs, the brain and the body tissues. O₂, CO₂ and N₂ are carried through the system. On the basis of this fact, the external respiration in the lungs and the internal respiration in the body tissues can be expressed by equilibrium functions, representing the gas exchange by the diffusion phenomenon, the variation of hydrogen ion concentration in the blood, and the quantity of oxidized hemoglobin. Utilizing the model, the variation of the respiratory system in response to the inspiration of air lacking O₂ as well as to the possible damage occurring within the system are investigated.