LQG based robust tracking control of blood gases during extracorporeal membrane oxygenation

The paper presents three different types of LQG based controllers designed for tracking control of the arterial partial pressures of the blood gases; oxygen and carbon dioxide (O₂ and CO₂) during extracorporeal membrane oxygenation (ECMO). ECMO is a method of support for the heart and or lungs in severely ill patients. In this procedure, the blood is circulated out of the body and into an ECMO machine where the O₂ and CO₂ gas levels are restored before being pumped back into the body. The performance of each of the controllers was ascertained both from a tracking as well as disturbance rejection standpoint to step commands in both these inputs. Robustness analysis was also performed on all the closed loop configurations using the structured singular value analysis. The uncertainty was considered to be of a structured parametric type and was captured by the perturbation of the system "A" matrix. Performance of all the controllers was tuned so as to ensure robust stability to these parametric uncertainties. The LQG and LQG/LTR with feed forward control were able to achieve good tracking performance. But, only the LQG augmented with integral control was able to achieve accurate tracking of the arterial partial pressures of the blood gases in the presence of a step input disturbance in the blood gases flow rates.