Presents a model concerning interaction of hemodynamics and gas exchange, which involves two physiological systems-respiratory and circulatory systems. It consists of five components: a model of gas transport, exchange and storage in the human, a multi-element nonlinear mathematical model of human circulatory system, an alveolar ventilation controller, a cardiac output controller, and a controller of frequency of breathing. Model simulations provided results of both dynamic and steady-state responses under low oxygen (hypoxia), which can reflect the interaction of hemodynamics and gas exchange. By using this model, the changes of pulmonary arterial pressure and right ventricular pressure in high altitude, which may cause mountain sickness, are discussed. Therefore, this model may be used to study reaction of hypoxia and the assist technologies.
A model of the human respiratory system is proposed which has a satisfactory performance under different physiological conditions. The model comprises a continuous plant and a discrete controller which generates and updates the drive signal to the plant at the end of every breath to represent the Hering-Breuer reflex. Arterial and central medullary sensors are included. The lung volume, dead space volume, cardiac output and cerebral blood flow are time varying. The respiratory work is minimized. The model is examined and simulation results of its performance in hypercapnia, hypoxia, periodic breathing and moderate exercise are presented. The responses presented include the relatively fast transients of Cheyne-Stokes breathing and the slower transients associated with carbon dioxide inhalation.
In this short note we prove that if X is a separably rationally connected variety over an algebraically closed field of positive characteristic, then H^1(X, O_X)=0.