Multivariable control design for artificial blood-gas exchange with heart-lung machine support

In this paper the design of a robust multivariable controller for the blood-gas exchange during cardiopulmonary-bypass with heart-lung machine support is presented. The proposed control strategy of the two-input-two-output oxygenation/decarbonisation process is divided into inner- and outercontrol loops. The inner-loop consists of input-output linearisation by state-feedback, which is extended with a Smith-like predictor for time-delay compensation and partially decouples the oxygenation exchange. The outer-control loop consists of a single linear multivariable controller, which is tuned via the ℋ_∞-loop shaping approach for robust performance and accounts for plant, linearisation and time-delay uncertainties. The controller was tested with an experimentally validated model of blood-gas exchange over the whole operating range and shows good results with respect to reference changes and disturbance rejection. The control strategy is suggested to improve patient´s safety during the cardiopulmonary bypass (CPB) procedure.