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Biomedical subjects

C Ribreau

Publications and source records attributed to C Ribreau.

5 recordsLinked to original sources
PubMed1989

Cross-sectional area measurement in collapsed tubes using the transformer principle.

To avoid the necessity for intraluminal catheters as used with the axial impedance method of measuring the cross-sectional area of flexible tubes independently of their shape, while retaining the advantage of an immediate electrical output, an electromagnetic method was tested. The method uses a single-turn sensing coil attached to or embedded in the tube wall at the site of interest as the secondary winding of a transformer. One or more primary coils coaxial with the tube provide an alternating magnetic field parallel to the tube axis, and the resulting secondary voltage, after amplification and demodulation, is directly proportional to tube cross-sectional area. Tube pressure/area relationships measured thus were compared with those measured using both an ultrasonic imaging technique and liquid volume displacement. The method was shown to provide an accurate and relatively simple alternative to the impedance method. Various ways to fabricate tubes with or otherwise introduce the necessary sensing coil are discussed.

Biomechanical Phenomena↗
PubMed1989

[Venous hemodynamics. Base equations].

The hydrodynamics in tubes with inert walls collapsed by a negative transmural pressure (inside pressure minus outside pressure) set up a fundamental and original approach in venous hemodynamics. Mechanisms of flow regulation and flow limitation can occur especially when the upstream pressure is held constant or when the average flow speed in a cross-section equals the local pressure waves speed. The three baseline equations on mechanics are required to demonstrate these properties: --the tube law, --the equation of motion, --the equation of continuity. It is shown that the behaviour of the tube varies with the nature of the flow (subcritical, critical or supercritical, subsonic, sonic or supersonic, according to the aerodynamics). Though this study does not take all the physiological and biological data into account, it includes indeed the three fundamental aspects on mechanics of the veins. The rheologic equation on the state of the venous wall, normal or pathologic, plays a major and determinant role.

Biomechanical Phenomena↗
PubMed1989

[Venous hemodynamics. Basic equations].

The hydrodynamics in tubes with inert walls collapsed by a negative transmural pressure (inside pressure minus outside pressure) set up a fundamental and original approach in venous hemodynamics. Mechanisms of flow regulation and flow limitation can occur especially when the upstream pressure is held constant or when the average flow speed in a cross-section equals the local speed of the pressure waves. Three baseline equations on mechanics are required to demonstrate these properties: the tube law, the equation of motion, the equation of continuity. It is shown that the behaviour of the tube varies with the nature of the flow (subcritical, critical or super-critical, subsonic, sonic or supersonic, according to the aerodynamics). Though this study does not take all the physiological and biological data into account, it includes indeed the three fundamental aspects on mechanics of the veins. The rheologic equation on the state of the venous wall, normal or pathologic, plays a major and determinant role.

Hemodynamics↗