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Biomedical subjects

T Mesana

Publications and source records attributed to T Mesana.

59 records · Page 4Linked to original sources
PubMedDate not supplied

Control of pulsatile rotary pumps without pressure sensors.

When ventricular assistance is achieved with a volumetric pump driven by an electric actuator, overpumping can cause venous collapse. To prevent this problem, pump speed must be monitored and controlled. The authors developed a regulatory system based on the current intensity signal from the electric motor. This signal is processed and compared with predicted values calculated according to a mathematical model at the beginning of each ejection phase. If a difference is detected, pump speed is adequately adjusted. The great advantage of this system is elimination of the need for an implantable pressure sensor. It requires a simple and ubiquitous electronic component, i.e., a resistor, that can be easily integrated into the motor control circuit and does not require calibration.

Animals↗
PubMedDate not supplied

Another way of pumping blood with a rotary but noncentrifugal pump for an artificial heart.

This article describes an alternative mode of pumping blood inside the body. The device is a non centrifugal, valveless, low speed rotary pump, electrically powered, based on Wankel engine principle. The authors developed an implantable electrical actuator resulting in a compact, sealed motor-pump unit with electrical and magnetic components insulated from fluids. The results in the flow curve and in the pumping action show some common points but also some basic differences compared to classical pulsatile pumps or centrifugal pumps. The blood coming from the atrium follows a continuous movement without any stop flow but with variations creating pulsatility. Ejection and filling of the pump are simultaneous. It is always an active filling. Hydraulic efficiency depends on clearance in the pumping chamber and outlet port pressure. A 60 cc device allows flows up to 8-9 liters. The implantable motor is cyclindrical in shape, has a moderate weight (490 grams) and presents a good efficiency (32% for a rotary speed of 90 rpm against a mean aortic pressure of 150 mm of Hg). The authors conclude that their device could be proposed after further experimental studies, as an LVAD for shortterm assistance with a good promise for permanent application.

Animals↗
PubMedDate not supplied

Thromboembolytic complications during circulatory assistance with a centrifugal pump in patients with valvular prostheses.

This article describes two patients with artificial heart valves who suffered thromboembolytic complications during circulatory assistance using a Biomedicus centrifugal pump. The first case involved a 25-year-old man who presented acute blockage of a mechanical aortic valve. Emergency surgery was performed to replace this valve with a bioprosthesis. Postoperatively the patient developed severe left heart insufficiency and a Biomedicus centrifugal pump was placed between the left atrium and the ascending aorta. After 3 days of total left ventricular assistance, weaning was started and successfully completed with explanation on the 5th day. Two days later the patient died of multiple coronary embolism with thrombosis of the valve. The second case involved a 30-year-old man. Six months before, he underwent surgical procedure with placement of Bio-prosthesis for dissecting aortic aneurysm due to annuloectasia. Upon admission for terminal dilated myocardiopathy, the patient was in kidney failure almost requiring dialysis. Because of this patient's size (Marfan syndrome), no donor heart was immediately available and left circulatory assistance with a Biomedicus pump had to be initiated. The patient lived without mechanical ventilation, in good clinical condition until day 23 when he presented acute right heart failure due to extensive valvular and coronary thrombosis. From these two cases, several important comments can be made about anticoagulation therapy, partial unloading of left ventricle, or need for biventricular assistance, and efficiency of centrifugal devices in these clinical applications.

Adult↗
PubMedDate not supplied

Control of a rotary pulsatile cardiac assist pump driven by an electric motor without a pressure sensor to avoid collapse of the pump inlet.

Our ventricular assist device uses a valveless volumetric pump operating on the Maillard-Wankel rotary principle. It is driven by an electric motor and provides a semi pulsatile flow. At each cycle, blood is actively aspirated into the device, and overpumping results in collapse at the pump inlet. To prevent overpumping, it is necessary to ensure that pump intake does not exceed venous return. Poor long-term reliability rules out the use of current implantable pressure sensors for this purpose. To resolve this problem, we have developed a method of control based on monitoring of the intensity of electric current consumed by the motor. The method consists of real time monitoring of current intensity at the beginning of each pump cycle. A sudden change in intensity indicates underfilling, and motor speed is reduced to prevent collapse. The current consumed by the motor also depends on the afterload, but the form of the signal remains the same when afterload changes. After demonstrating the feasibility of this technique in a simulator, we are now testing it in animals. We were able to detect and prevent collapse due to overpumping by the cardiac assist device. This system also enables us to know the maximum possible assistance and to thus adapt assistance to the user.

Algorithms↗