Article révisé par les pairs
Résumé : The authors describe the system they developed for the investigation of O2-CO2 transport in patients under controlled ventilation. The system is made up of two components: the instruments under computer control and the mathematical models implemented on a computer. Most of the measurements are obtained continuously in the inspired and expired gases (flow, pressure, oxygen, carbon dioxide and nitrogen partial pressures), in the blood of the radial artery (oxygen tension and saturation, blood pH, temperature) and in the mixed venous blood (oxygen saturation). Additional in vitro measurements are also collected. The analog signals are processed in real time by a PDP 11-34 computer. To these so-called passive observations are added continuous observations of the response of the body to various perturbations which are applied under computer control. So far we have investigated the nitrogen (or oxygen) washout and short-duration step inhalation of carbon dioxide. From these observations we estimate the functional residual capacity, the continuous distribution of specific ventilation and pulmonary capillary perfusion. All our observations are meaningless unless we refer them to knowledge which is not contained in the data themselves: we have developed mathematical models which explicitly describe the relationships through which we can infer from our observations, informations about the underlying physiological processes. The solution of the differential equations of the model by a computer (PDP 11-60) makes it possible to simulate the real and observable phenomena. We present the first results obtained with this system. We discuss the methodology and some of the problems which arose during its implementation.