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Biomedical subjects

B Candelon

Publications and source records attributed to B Candelon.

6 recordsLinked to original sources
PubMed1992

Hemocompatibility of titanium nitride.

The left ventricular assist device is based on the principle of the Maillard-Wenkel rotative pump. The materials which make up the pump must present particular mechanical, tribological, thermal and chemical properties. Titanium nitride (TiN) because of its surface properties and graphite because of its bulk characteristics have been chosen. The present study evaluated the in vitro hemocompatibility of TiN coating deposited by the chemical vapor deposition process. Protein adsorption, platelet retention and hemolysis tests have been carried out. In spite of some disparities, the TiN behavior towards albumin and fibrinogen is interesting, compared with the one of a reference medical grade elastomer. The platelet retention test gives similar results as those achieved with the same elastomer. The hemolysis percentage is near to zero. TiN shows interesting characteristics, as far as mechanical and tribological problems are concerned, and presents very encouraging blood tolerability properties.

Adsorption↗
PubMed1984

The importance of software programmable pacemakers: in vivo programming of a prototype device.

Recently, we have developed microcomputer-oriented pacemakers with true software flexibility. The first 25 devices implanted (DPG-1 type) exhibited an unexpected phenomenon caused by a microcomputer error. A safety mechanism switched off all special functions and automatically reset all parameters to standard settings. The problem was solved by noninvasive modification of the software. More than 200 units (TX-1 type), which are rate responsive pacemakers based on the QT principal, were implanted up to May 1984. These pacemakers were built using the same microelectronics as used in the DPG 1 pacemaker. Knowledge gained from clinical evaluation was directly applied not only to the patients receiving new implants but also to the preexisting implantees. This was done by software reprogramming in the implanted unit.

Arrhythmias, Cardiac↗
PubMed1980

[Continuous assay of blood lactates. Application to the study of muscular work in the arteritis patient].

Ten normal and twenty arteriosclerotic patients underwent two successive static continuous exercise tests: - 4 minutes holding of 30% maximum power - 1 minute holding of 60% maximum power. Simultaneous recordings were made of: - The Xenon 133 washout curve of the anterior tibial muscle, to assess the ischaemia induced by exercise and to measure the duration of the hyperaemic phase; - The continuous lactate level in the femoral vein, using an original electrode specific for these enzymes. The following parameters were retained; - Resting, peak and the surface of accumulation of lactate after exercise; - The appearance time and the duration of accumulation of lactate with respect to the length of the hyperaemic phase. The following conclusions are drawn: - The differences in the height of the peak of the serum lactate. The duration and the surface of accumulation of lactate were only significant in obviously arteriosclerotic patients in whom exercise had induced ischaemia. - From the dynamic point of view: the hyperaemic phase always preceded the phase of venous accumulation of lactate, in all groups, peak lactates levels always occured during the hyperaemic phase and the length of the accumulation phase was 2 to 3 times that of the hyperaemic phase; in this respect, there was a significant difference between obvious arteriosclerotic patients in whom exercise induced ischaemia, and a group of other arteriosclerotic and normal patients.

Adult↗
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↗