Method and apparatus for invasively measuring cardiac output by detecting temperature differences of blood heated by radiation
First Claim
1. A cardiac output measurement system, comprising:
- a catheter adapted to be inserted through an atrium of a heart;
an emitter disposed in said catheter for emitting radiation to volumetrically heat a definable volume of blood that passes through said atrium, said radiation being absorbed by the blood and converted into heat;
a temperature sensitive element disposed downstream from said emitter for generating a signal corresponding to the temperature of the blood downstream from said emitter; and
control means for controlling the application of said radiation.
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Abstract
A cardiac output measurement device volumetrically heating a predefined quantity of blood flowing through a heart by arbitrarily applying a containable energy field to the blood using a thermodilution catheter having an emitter that uniformly emits electromagnetic radiation. Blood temperature is measured at the pulmonary artery by a sensor that provides a signal representing the temperature of the mixed blood to a controller. The controller determines the flow rate, or cardiac output, by performing a heat balance analysis based upon the applied power and resultant blood temperature. The cardiac output measurement device includes a catheter having an emitter and, preferably, a temperature sensor located at its distal end. The catheter is coupled to a laser or other energy source capable of generating containable electromagnetic radiation, such as an ultraviolet or microwave energy source. Significantly, for the preferred laser source, the emitter is a diffuser that uniformly emits the laser-generated energy into a predetermined volume of flowing blood. A temperature measuring system of the controller receives temperature signals from the sensor and generates a resultant temporal temperature profile used by a flow estimator to determine the flow rate and generate a power excitation function to control the energy source. The resultant measured flow may also be presented though a user interface.
43 Citations
37 Claims
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1. A cardiac output measurement system, comprising:
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a catheter adapted to be inserted through an atrium of a heart; an emitter disposed in said catheter for emitting radiation to volumetrically heat a definable volume of blood that passes through said atrium, said radiation being absorbed by the blood and converted into heat; a temperature sensitive element disposed downstream from said emitter for generating a signal corresponding to the temperature of the blood downstream from said emitter; and control means for controlling the application of said radiation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A catheter for use in a cardiac measurement system having an energy source, comprising:
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an elongated member configured to be inserted through an atrium of the heart; an emitter disposed in said member and using energy from said source to emit radiation to volumetrically heat a definable volume of blood that passes through said atrium, said radiation being absorbed by the blood and converted into heat; and a temperature sensitive element disposed in said member downstream from said emitter for generating a signal corresponding to the temperature of the blood downstream from said emitter. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. An apparatus for measuring fluid flow rate in a passageway, comprising:
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an elongated member adapted to be inserted into flowing fluid; an emitter, coupled to said elongated member, for emitting radiation to volumetrically heat a definable volume of flowing fluid, said radiation being absorbed by the flowing fluid and converted into heat; a temperature sensitive element, located downstream from said emitting means, for generating a signal corresponding to the temperature of the flowing fluid downstream from said emitting means; and control means for controlling the application of said radiation. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. A method of measuring the volumetric flow rate of a fluid flowing from an upstream location towards a downstream location, comprising the steps of:
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(1) inserting an elongated member into flowing fluid; (2) sensing the baseline temperature of the flowing fluid; (3) emitting, from an emitter coupled to said member, radiation to volumetrically heat a definable volume of flowing fluid, said radiation being absorbed by the flowing fluid and converted into heat; (4) sensing the temperature of the flowing fluid downstream from said emitter; (5) determining a volumetric flow rate of the flowing fluid in accordance with said temperatures and said emitted radiation. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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Specification