| Abstrakt: |
Extracorporeal circulation (ECC) is a technique which substitutes the pulmonary and cardiac functions of a patient during open heart surgery. Closed loop control of ECC can prevent some of the risks attached to the use of this technique. The ECC consists of strongly interconnected hemodynamic, biochemical and thermodynamic sub-systems. To come to global modelling and control of the cardiopulmonary bypass, ECC is described in terms of the control theory concepts : command, disturbance, state, output, parameter, reference and constraints. If ECC is considered in the hypothermic phase, four sub-systems can be distinguished. These sub-systems are characterized by their state variables : hematocrit, blood volumes, vasomotor tone and blood gases and buffer capacity. The need for nonlinear models and/or adaptive control is noted. A simulation model for ECC hemodynamics is given. |
