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Ex vivobioimpedance data measured on normal and cancerous female breast tissues are reported. They clearly show that the electrical properties of normal tissues, surrounding tissues, and carcinoma are different. These differences lie in the conductivity, in the characteristic frequency (frequency of the maximum of the imaginary part of the bioimpedance), and also in the shape of the Bode plots. Modeling using an R-S-Zcpemodel is reported as well as indexes extracted from the real and imaginary parts of the bioimpedance. Even if a classification of the different types of tissues remains a difficult task and leads to much less precise diagnosis than microscopic examination, the electrical behavior of mammary tissue could be used to develop a noninvasive technique for early breast cancer detection.

Abstract: An experimental system for impedance tomography has been constructed. The acquisition system uses 16 multifunctional active electrodes, each including a current source and a voltage buffer. Images of active and reactive parts of different target impedances in a phantom filled with liquid have been obtained. The system performance has been compared with those of other systems using either a mesh phantom or rods as point sources used for the determination of the modulation transfer function.

Without Abstract:

Maintenance of a constant level in the oxygenator during surgical extracorporeal circulation (ECC) is of paramount importance. We propose a device able to regulate the pump speed accordingly to the level in the oxygenator, and an automatic clamp to control venous return from the patient.The level regulator permits pump speed control and also stops the pump when a prefixed low level is reached (during ECC). Linearization of the level sensor has been made in order to optimize the PI regulator. Simulation results are presented and the regulator is evaluated in a clinical environment.The automatic clamp provides a good solution for reproducible and easy transitions in venous return. When coupled with the level regulator, the pump speed will increase automatically from zero to the correct equilibrium speed, with variable duration (from 30 seconds to 5 minutes) chosen by the operator. The same technique is used for stopping the ECC.These two devices are, in fact, modules, making up part of an evolutive device for ECC automation. The modules can exchange data with a supervising microcomputer.

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.

A prototype for the control of blood gases during extracorporeal circulation (ECC) has been built. It is composed of a CDI300 continuous gas blood analyzer, a programmable gas blender and an IBM PC. The air blender is composed of three mass flow controllers (air, oxygen and total flow rate). The microcomputer commands these controllers in order to obtain the desired mixture of air and oxygen. The system acquires the data sent by the blood gas analyzer every 6 seconds and commands the gas blender in order to maintain the desired arterial dioxide partial pressure (PaCO2) in the arterial line. The first experimental results on sheep show that if blood gas parameters are stable when beginning the closed loop control, then the desired PaCO2value may be obtained. Otherwise, the value of PaCO2under control is slightly different but a stable value is obtained after 10 minutes. More experiments must be done in order to establish the real limits of such a system and optimize the gain of the control system.

Les quelques lignes qui suivent ont été réalisées en tant qu’introduction aux journees d’étude annuelles du CDI les 14 et 15 décembre 2020 : « Traiter les spasticités ». Il s’agissait de se préparer à entendre les différents intervenants en restituant des éléments de contexte de la spasticité : sa définition au fil du temps, les propositions d’évaluations et de traitements, la place de ce concept dans la réadaptation contemporaine, le partage de la « vision de l’intérieur » d’Alexandre, jeune patient de 25 ans.