Biomedical subjects

A Rouane

Publications and source records attributed to A Rouane.

5 recordsLinked to original sources

PubMed2003

Dielectric properties of blood: an investigation of haematocrit dependence.

We have investigated the haematocrit dependence of the electrical parameters (relative permittivity and conductivity) of blood. The measuring set-up, composed of an impedancemeter (HP 4291 A), an open-ended coaxial line and a temperature controlling set, was designed for dielectric measurements in the 1 MHz to 1 GHz frequency range. Measurements were performed on ex vivo animal (cow and sheep) blood at 37 degrees C. The two dielectric parameters appeared to be strongly dependent on the haematocrit. The permittivity versus frequency decreases then increases when the haematocrit decreases. The conductivity increases in the whole frequency range when the haematocrit decreases. Due to the lack of comparative data on the frequency range explored, we compare the dielectric profiles with those deduced from the Maxwell-Fricke theoretical model.

Animals↗

PubMed2002

Catheter ablation using very high frequency current: effects on the atrioventricular junction and ventricular myocardium in sheep.

BACKGROUND: Radiofrequency ablation is currently used in the treatment of various cardiac arrhythmias. However, this technique is limited by impedance rise, leading to coagulum formation and desiccation of tissue. We developed a new generator, providing very high frequency (27 MHz) current, which is in the intermediate range between radiofrequency and microwave energy. The aim of this study was to evaluate the results for catheter ablation of the atrioventricular junction and characteristics of the lesions obtained at ventricular sites. METHODS AND RESULTS: The generator was coupled to a specially designed 7-French coaxial catheter. The study included experiments performed on 10 sheep (Wt. 31- 42 kg). In seven sheep, the catheter was introduced into the femoral vein and advanced across the tricuspid annulus to record the largest possible His electrogram. VHF current was applied for 25 s, with increasing energies. The energy needed to obtain complete atrioventricular (AV) block ranged from 60 to 100 Watts. Six animals were observed for 6 to 21 days. Complete AV block was found to be persistent. In those seven sheep in whom AV junction was ablated and in three additional sheep, the ablation catheter was positioned toward the right ventricular apex using the same approach and into the left ventricle via the femoral artery, and 20 to 90 Watts energy was delivered in order to assess the size of the induced lesions. Side effects included ventricular tachycardia degenerating into ventricular fibrillation in six cases, but the same effect was observed in this animal model with radiofrequency energy. No cardiac perforation was noted. No thrombus was observed at the catheter tip. The size of the lesion ranged from 3 to 45 mm in width and 1 to 15 mm in depth. CONCLUSIONS: Catheter ablation using VHF current is feasible and appears effective in producing stable AV block when applied at the AV junction and results in substantial myocardial lesions. Further studies are needed to define its clinical interest and side effects.

Animals↗

PubMed1995

Intracardiac high-frequency catheter ablatherapy: technical aspects.

Arrhythmia and conduction disorders can be treated by intracardiac ablation. The paper presents an original intracardiac catheter ablation method using a high-frequency (HF) electromagnetic power source. A high-frequency signal is emitted through an electrophysiological catheter introduced into the femoral vein and passed along the course of that vein into the heart. To prevent impedance rise, a problem encountered with other techniques, HF signal wave trains are used for half-period impedance match control and, where necessary, automatic impedance adjustment. Fully automated impedance matching combined with frequency-specific catheter design prevents power reflection between load and source. Resulting lesions can be controlled as to location, area and depth. In addition, HF pulses can be released independently of cardiac rhythm. Additional comprehensive animal experimentation is currently going forward.

Animals↗

PubMedDate not supplied

Study of a new electromagnetic sensor for glycaemia measurement: in vitro results on blood pig.

In this paper, we develop a non-invasive method to measure glycaemia levels. The method is based on an electromagnetic sensor associated with a specific electronic card. Results obtained on whole pig blood show the influence of the temperature and the linearity between the glucose concentration and the process card signal output. Measurements are reproducible and the resolution obtained permits determination of the glucose level around 0.1 g l(-1).

Animals↗

PubMedDate not supplied

Non-invasive glycaemia blood measurements by electromagnetic sensor: study in static and dynamic blood circulation.

In this paper, we present the results of non-invasive blood glycaemia measurements. The blood used in the measurements was calf blood. The measurement method uses an electromagnetic sensor based on eddy currents, which allows the detection of blood glycaemia levels through the variation of the dielectric parameters of the blood. A change in blood glucose concentration causes a variation in the dielectric parameters, in particular conductivity. Detection is only possible at a resonant frequency. The measurements were taken in a static and dynamic state (with and without circulation of blood). The blood is inside a plastic tube placed within the sensor and is surrounded by gelatine, which simulates muscular tissue. The plastic tube simulates the vein where blood circulation occurs. The in vitro results in both cases (static and dynamic) are provided. Under unfavourable conditions we can detect a change of +/- 2 g/l of glucose. We present and discuss these results.

Animals↗