Surgery – Truss – Pad
Patent
1989-01-11
1990-07-17
Green, Randall L.
Surgery
Truss
Pad
128657, 128667, 128672, 128772, 128748, A61B 500
Patent
active
049414739
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In radiographic examinations of the cardiac and vascular systems, catheters, i.e. thin plastic tubing, are utilised in several ways. Contrast liquid can be injected via the catheter for making parts of the vascular system visible on exposure to X-rays. Blood tests can be taken for analysis of dissolved gases, pH value, ion concentration etc. Hydrostatic pressure can be measured by a pressure transducer indicator connected to the catheter.
Catheters are not only used for diagnostic purposes, however. A new form of treatment of vascular constriction utilises catheters which are expandable by a heavy hydrostatic pressure being applied in a cavity, these being known as ballon catheters. In addition, pharmaceutical preparations can be injected through catheters for local drug administration.
For the end of the catheter to reach the desired place in the cardiac and vascular systems, a so-called guide wire is used, the latter being in the form of a wire with a dimension allowing its insertion into the catheter. Typical dimensions for catheters are: outside diameter 1-3 mm, inside diameter 0.5-1.5 mm, length 80-150 cm. The diameter of the guide wire may be about 0.5-1.0 mm. While the catheter is made from a polymer material, the guide wire is most usually made up from a metallic material, generally stainless steel.
In measuring pressure with known apparatus, the pressure is transmitted hydraulically in the catheter. This is problematical, due to the transmission properties of catheter/pressure transducer system. Furthermore, microscopic air bubbles can cause considerable deterioration in the transmission. This measurement is thus not reliable.
SUMMARY OF THE INVENTION
The present invention solves this and associated problems by the use of a miniaturised sensor placed near the distal end of the guide wire (the end nearest the sampling location), the signal transmission from the sensor taking place optically via an optical fibre built into the leader.
By the small dimensions enabled due to fibre-optic technology, the guide wire may be given such mechanical properties in the form of bending and torsional stiffness, and such formability as are required for its function of leading the catheter up to the sampling location in the cardiac and vascular systems. The optical signal transmission is not burdened with the deficiencies in transmission pertaining to the hydraulic principle.
Apart from more reliable diagnostic measuring values there is also obtained simpler handling. As a result of the extremely small dimensions of the pressure sensor and guide wire, pressure measurements can be made at points in the cardiac and vascular systems which have previously been inaccessible.
The distinguishing features characterizing the invention are apparent from the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention will now be described with reference to the Figures, in which
FIG. 1 illustrates a basic embodiment of the guide wire in accordance with the invention where certain portions have been broken away,
FIG. 1A is a cross-sectional view taken along lines A--A of FIG. 1, and
FIG. 2 is a detail of a special embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIG. 1, it will be seen that the pressure sensor 1 is placed close to the distal end 2 of the leader. Within the framework of what is possible to achieve using fibre-optical technology and micromechanics, a plurality of detailed embodiments of the sensor are conceivable, e.g. the one described in the Swedish patent application 8602836-2. The optical fibre 3 extends along the entire length of the guide wire and merges into a connection means 9 at the proximal end. Using the connection means, the fibre 3 can be connected with insignificant optical losses to another fibre or to an arrangement with a light source and a light detector. The pressure sensor 1 is mechanically connected, for example, by a welded joint 10 or by brazing to a sleeve 5, which comprises a helically wo
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Engstrom Thomas
Hook Bertil
Tenerz Lars
Green Randall L.
Radisensor AB
Shay Randy
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