Artificial organs
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A control strategy for rotary blood pumps meeting different user-selectable control objectives is proposed: maximum support with the highest feasible flow rate versus medium support with maximum ventricular washout and controlled opening of the aortic valve (AoV). A pulsatility index (PI) is calculated from the pressure difference, which is deduced from the axial thrust measured by the magnetic bearing of the pump. The gradient of PI with respect to pump speed (GPI) is estimated via online system identification. ⋯ For maximum support, a low PI was maintained without inducing ventricular collapse. For maximum washout, the pump worked at a high PI in the transition region between the opening and the permanently closed AoV. The cascaded control of GPI and PI is able to meet different control objectives and is worth testing in vitro and in vivo.
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We present a regimen for anticoagulation in the immediate postoperative period after left ventricular assist device (LVAD) implantation using low molecular weight heparin (LMWH) as an alternative to unfractionated heparin. Between May and September 2007, eight consecutive patients undergoing LVAD implantation for advanced heart failure received the LMWH nadroparin. Nadroparin was given twice daily to achieve anti-Factor Xa activity target peak levels of 0.4 +/- 0.1 U/mL. ⋯ In two patients, pump thrombosis was suspected. There were two ischemic and no hemorrhagic strokes. The use of LMWH may provide a new anticoagulation treatment option in the immediate postoperative period after LVAD implantation.
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During the use of pulsatile extracorporeal life support (pulsatile-ECLS), the patient's venous pressure near the inlet venous catheter tip must be monitored to maintain sufficient blood flow and to prevent vein collapse. However, direct measurement of the venous pressure and the estimate of suction using measured blood inflow and prepump pressure are not practical because of setup difficulties during emergency treatments and in cardiovascular operations. In this article, we describe a new method for estimating the venous pressure that can be implemented in the controller of the pulsatile-ECLS system, the T-PLS. ⋯ Previously measured values of the pulsatile-ECLS compliance and the hemodynamic resistance along the inflow path are used to evaluate venous pressure with estimated blood flow. Estimated prepump pressure, inflow, and venous pressure were compared to the measured data in a series of in vitro experiments. The estimated venous pressure was used to avoid vein collapse and to increase the reliability in animal experiments.