Surgery – Truss – Pad
Patent
1985-09-13
1993-01-12
Pellegrino, Stephen C.
Surgery
Truss
Pad
128673, 128666, 128667, 7386142, 7386152, 356345, 356352, A61B 502
Patent
active
051781530
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTION
This invention is directed to means for measuring fluid flow in arteries and veins of mammals wherein the measurements are provided by differential pressure sensing means positioned in the fluid conduit. With the differential pressure and the knowledge of the cross-sectional area of the conduit, flow rates can be determined. In in vivo flow rate measurements, the diameter of the artery is determined using one of several techniques, such as direct measurement with a probe, two differential pressure measurements, by dye or thermal dilution methods, and by means of x-rays. The invention also has industrial application.
BACKGROUND OF THE PRIOR ART
Means to measure pressure in the human blood stream by a number of techniques are known. However, blood pressure alone fails to provide answers to many questions, such as: whether sufficient volume of blood to satisfy body needs is flowing, the condition of arteries and veins, and the existence of partial blockages that reduce blood flow to critical areas of the body. It is only by determining actual rate and volume of flow that the medical practitioner is provided with greater insight into the actual condition of the circulatory system.
The present invention provides means whereby fluid flow in vivo may be readily determined and in general, the invention comprises one or more fiber optic differential fluid-pressure measuring devices each comprising a first optical fiber sensor and means for positioning the first optical fiber sensor in the flow path at the measurement point. If the devices further consist of several optical fiber sensors, each includes a means for positioning the sensor relative to the measuring position and to each other. In each case, a means for forming a fixed or variable constriction in the flow path of the fluid may be employed. Means are associated with the constriction for positioning the associated optical fiber sensor in the flow path of the fluid at the constriction. The device further includes one or more fiber optic interferometers having either a single leg or a pair of legs with means connecting each of the optical fiber sensors in a leg of an interferometer. Radiant energy is directed into the legs of the interferometers and through each of the sensors; and radiant energy detecting means are connected to the interferometers. The fiber optic probe described may be used in a wide range of veins and arteries (large and small). One specific example chosen for illustration will be the measurement of total cardiac output.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more particularly described in reference to the accompanying drawings wherein:
FIG. 1 is a chart illustrating cardiac indices at different ages of a human being;
FIG. 2 is a chart illustrating events of a cardiac cycle showing changes in the left arterial pressure, left ventricular pressure, aortic pressure, ventricular volume, the electrocardiogram and the phonocardiogram;
FIG. 3 illustrates diagramatically a Mach-Zehnder interferometer and associated demodulation electronics;
FIG. 4 is a schematic view like FIG. 3 of a Michelson interferometer and associated demodulation electronics;
FIG. 5 is a diagramatic showing of a fiber optic Michelson interferometer with phase-locked-loop homodyne detection;
FIG. 6 is a schematic showing of a fiber optic Fabry-Perot interferometer and associated electronics for a pressure measuring device;
FIG. 6A is a view like FIG. 6 showing a pair of Fabry-Perot interferometers with one sensor in each of the pair of interferometers for measuring differential pressure and measuring fluid flow;
FIGS. 7A and 7B graphically illustrate photo detector output current and its derivative resulting from light wave phase-change fiber optic sensor output;
FIG. 8 schematically illustrates a phase-locked-loop homodyne detection circuit;
FIG. 9 graphically illustrates the sensitivity of fiber optic homodyne sensor at 0.degree. and 90.degree. bias angle;
FIG. 10 schematically illustrates a technique for reducing optical feedback in a
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Pellegrino Stephen C.
Shay David
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