Adaptive predictive control of dissolved oxygen concentration in a laboratory-scale bioreactor.

We present an algorithm for the adaptive control of dissolved oxygen concentration in a bioreactor, based on the agitation rate. The dynamics are represented by an incremental first-order model with variable dead-time and parameters. These are estimated on-line by a recursive least-squares identification method with a forgetting factor and a constant sensitivity. The model is employed to predict the behaviour of the dissolved oxygen concentration over a finite horizon, using an original method which requires little computation. Then, a Generalized Predictive Control optimisation strategy computes the agitation rate from the predictions and the desired set point, while gradually updating the controller smoothness. This algorithm, which requires little preliminary knowledge, has been implemented on a laboratory-scale fed-batch bioreactor for which the use of conventional controllers showed limited performance, due to the unpredictable and evolutive nature of the dynamics. The new controller proved to be robust and effective over a wide range of operating conditions, while requiring no operator adjustments.

[Blood saving in bone prosthetic surgery. Apropos of 426 cases]. / Economie de sang en chirurgie osseuse prothétique. A propos de 426 observations.

Perioperative blood salvage during hip and knee prosthetic surgery have been evaluated in a series of 345 patients who underwent a total of 426 surgical procedures. In 85 per cent of the cases, no additional homologous transfusion was required. In the patients who benefited from autotransfusion the quantity of bank blood transfused was 10 times less than in patients who were not autotransfused.

[Bilateral prosthesis of the knee in a hemophilia A patient with an inhibitor]. / Prothèse bilatérale de genou chez un hémophile A avec inhibiteur.

A forty-one year old severe haemophiliac A (factor VIII less than 1%) complicated by an antifactor VIII inhibitor was operated on for a bilateral arthroplasty of the knees. Substitutive treatment was started by giving anti-haemophilic A cryoprecipitate at a dose of 40 IU . kg-1. The anamnestic response occurred at day 6. Consumption of the inhibitor begun with the injection of 50,000 IU of concentrated factor VIII. This method proved to be insufficient for mastering the haemorrhagic syndrome, because the antibody titre quickly reached 10 IU Oxford. Treatment was continued with Autoplex (100 IU . kg-1), during three weeks, without any clinical or biological complications. It is suggested that Autoplex be used as the substitutive treatment in cases of major surgery in severe haemophilia complicated by a factor VIII inhibitor.