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Biomedical subjects

I Dion

Publications and source records attributed to I Dion.

12 recordsLinked to original sources
PubMed1998

Cardiovascular disease. Physician attitudes toward prevention and treatment.

OBJECTIVE: Survey of physician attitudes toward practising cardiovascular disease prevention. DESIGN: Questionnaire administered via telecommunication from 1992 through 1994. SETTING: The FAMUS (Family Medicine, University of Sherbrooke) project, between 1992 and 1996, used weekly telecommunication to collect data from 200 general practitioners throughout the province of Quebec on cardiovascular disease risk factors and their treatment. PARTICIPANTS: Of 200 physicians contributing to the FAMUS project, 156 completed questionnaires (response rate 78%). MAIN OUTCOME MEASURES: Variations in attitudes to prevention policy and risk factor interventions. RESULTS: Survey results revealed physicians knew important risk factors for cardiovascular disease but differed in attitudes toward efficacy of treatment. Intervention to control cholesterol was thought to be very effective by 21.2% (95% confidence interval [CI] 21.2 +/- 6.4) and without effect by 10.3% (95% CI 10.3 +/- 4.8). Intervention to improve dietary habits was considered ineffective by 48.1% (95% CI 48.1 +/- 7.8). Confidence in managing risk factors varied; most respondents described themselves as only moderately skilled. A few practitioners (30.1%; 95% CI 30.1 +/- 7.2) acknowledged practice guidelines as an important source of information on which to base preventive interventions. Only 14.7% (95% CI 14.7 +/- 5.6) of those surveyed included remuneration as contributing to their implementation of prevention activities in practice. CONCLUSIONS: Variations in physician attitudes could influence risk factor intervention. Interventions to change lifestyle are associated with uncertainty about patient compliance, efficacy of treatment, and ability to effect lifestyle changes.

Adult↗
PubMed1997

Physico-chemistry and cytotoxicity of ceramics: part I: characterization of ceramic powders.

The morphology of Al2O3, ZrO2/Y2O3, AIN, B4C, BN, SiC, Si3N4, TiB2, TiC, TiN ceramic, graphite and diamond powders has been studied by scanning electron microscopy (SEM) and the specific area of each powder was determined with the BET method. X-ray diffraction (XRD) investigations have been carried out in order to evaluate the crystallinity and determine the constitutive phases. The chemical composition was assessed by classical chemical analyses and by X-ray microprobe; some powders were studied by the laser micro-Raman technique. Correlations have been established between all these results.

Journal Article↗
PubMed1997

Cora rotary pump for implantable left ventricular assist device: biomaterial aspects.

Our group is developing a left ventricular assist device based on the principle of the Maillard-Wankel rotative compressor: it is a rotary, not centrifugal, pump that produces a pulsatile flow. Stringent requirements have been defined for construction materials. They must be light, yet sufficiently hard and rigid, and able to be machined with high precision. The friction coefficient must be low and the wear resistance high. The materials must be chemically inert and not deformable. Also, the materials must be biocompatible, and the blood contacting surface must be hemocompatible. We assessed the materials in terms of physiochemistry, mechanics, and tribology to select the best for hemocompatibility (determined by studies of protein adsorption; platelet, leukocyte, and red cell retention; and hemolysis, among other measurements) and biocompatibility (determined by measurement of complement activation and toxicity, among other criteria). Of the materials tested, for short- and middle-term assistance, we chose titanium alloy (Ti6Al4V) and alumina ceramic (Al2O3) and for long-term and permanent use, composite materials (TiN coating on graphite). We saw that the polishing process of the substrate must be improved. For the future, the best coating material would be diamond-like carbon (DLC) or crystalline diamond coating.

Adsorption↗
PubMed1993

TiN coating: surface characterization and haemocompatibility.

The left ventricular assist device under consideration is based on the principle of the Maillard-Wankel rotary pump. The construction materials must meet stringent requirements. Titanium nitride was chosen for its surface properties and graphite for its bulk characteristics. The purpose of this study was to characterize the chemical vapour deposition titanium nitride coating via morphology, roughness, crystallinity, chemical composition, to report and discuss the results of in vitro haemocompatibility tests (protein adsorption, platelet retention, haemolysis) and to discuss physico-chemical and biological results. This chemical vapour deposition titanium nitride coating is well tolerated by the blood despite its surface irregularities, and appears as a good candidate material after improvements.

Absorption↗
PubMed1993

Ex vivo leucocyte adhesion and protein adsorption on TiN.

Titanium nitride (TiN) is regarded as a potential biomaterial for blood-contact applications. Its in vitro haemocompatibility has been evaluated already and gave promising results. The purpose of this study was to continue studying its 'biological' behaviour through an ex vivo evaluation. The material was a physical vapour deposition elaborated TiN coating and the phenomena observed were leucocyte adhesion and albumin and fibrinogen adsorption. These ex vivo results were compared with in vitro results obtained previously. Two reference medical grade silicone elastomer and three TiN arterio-arterial extra-corporeal circuits were tested. No leucocyte was retained by TiN, as in in vitro experiments; the ex vivo fibrinogen adsorbed quantity was higher and albumin adsorption was about the same in in vitro and in ex vivo situations. TiN can be considered as a suitable blood-contacting material.

Adsorption↗
PubMed1993

Blood haemolysis by ceramics.

Ceramics are more and more frequently under consideration for construction of blood-contacting devices, i.e. cardiac valves or cardiac assist devices. This study evaluated the haemolysis eventually initiated in vitro by ceramic powders (Al2O3, ZrO2/Y2O3, AlN, B4C, BN, SiC, Si3 N4, TiB2, TiN, TiC), graphite and diamond. The chemical composition of the powders was studied by X-ray microprobe and various other methods, and BET specific areas were determined. The haemolysis was almost zero for all powders, except AlN which showed slight haemolysis and TiB2 which had high haemolytic power.

Aluminum↗
PubMed1993

Haemocompatibility of Ti6A14V alloy.

Ti6A14V alloy has been mainly used as a biomaterial in the orthopaedic field. The present study describes the surface state of the Ti6A14V material and evaluates its in vitro haemocompatibility in terms of protein adsorption, platelet retention and haemolysis. The behaviour of the Ti6A14V alloy towards albumin and fibrinogen was compared to that of a reference medical-grade elastomer. The platelet retention test gave better results than those achieved with the elastomer. The haemolysis percentage of the alloy was almost zero. These results indicate that the Ti6A14V alloy is well tolerated by blood.

Adsorption↗
PubMed1993

A new model to test platelet adhesion under dynamic conditions. Application to the evaluation of a titanium nitride coating.

In order to evaluate under dynamic circumstances the in vitro platelet adhesion induced by rigid materials such as ceramic coatings deposited on selected substrates, a new model simulating a tube has been designed. In vitro platelet adhesion was assessed with this new model: the material was titanium nitride (TiN) deposited on Ti6A14V (TA6V) titanium alloy by a physical vapor deposition (PVD) process. The results were compared to those obtained with complete titanium carbide (TiC) graphite tubes coated with TiN by a chemical vapor deposition (CVD) process. The difference observed (less than 25%) in favour of the new system, could be due to the better surface state of the construction materials of this system. In fact it is a systemic error. However TiN confirms its good performance as a blood-contacting biomaterial.

Alloys↗
PubMed1993

Hemocompatibility of diamond-like carbon coating.

The new prosthetic heart valve that has been designed by FII Company and Pr. Baudet involves a new "composite" material: titanium alloy T16A14V coated with Diamond-like Carbon. The purpose of this study was to evaluate the in vitro hemocompatibility of this new material in terms of protein adsorption and platelet retention. The static protein adsorption test gave interesting results, particularly for the albumin assay (237%) compared to the results obtained with a silicone elastomer chosen as a reference; the fibrinogen quantity, adsorbed on the surface of the material was slightly higher than that adsorbed on the silicone surface. Platelets adhere quite twice as much as they do on the reference surface. Such investigations showed good hemocompatibility results and should initiate further studies.

Adsorption↗
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↗
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↗