Thermodilution catheter having a safe, flexible heating element
First Claim
1. A thermodilution catheter apparatus for making a thermodilution measurement, comprising:
- a flexible tubular catheter member adapted for introduction into a blood vessel of a patient, said catheter member having at least one lumen;
a flexible heating filament disposed with respect to said catheter member so as not to touch the patient'"'"'s blood when said catheter member is inserted into a blood vessel, the heating filament capable of being heated to apply a predetermined quantity of heat to blood in said blood vessel;
temperature detecting means for detecting downstream temperature variations of said blood as a result of the application of said predetermined quantity of heat to said blood;
means for providing a thermodilution measurement based on the detected temperature variations; and
wherein said heating filament can be slidably received into said at least one lumen.
1 Assignment
0 Petitions
Accused Products
Abstract
A thermodilution catheter having a heating filament which is fabricated so as to be thin and flexible enough to avoid contact with the patient'"'"'s blood. The heating filament is either inserted in a preformed catheter lumen, incorporated into a wall of the catheter body itself, or wrapped around the catheter body wall and surrounded by an external sheath. Generally, the covering of the heating filament is minimally thin so as to allow the heat from the heating filament to be transferred to the surrounding blood and to minimally increase the overall cross-sectional area. Since the heating filament does not directly touch the patient'"'"'s blood, the outer surface may be made smooth so as to prevent inducement of blood clots. In addition, the heating filament may be maintained at a safe temperature by forming the heating element of a flexible material having a high temperature coefficient of resistance, low thermal capacitance and high thermal conductivity. Preferably, the temperature coefficient of resistance of the material forming the heater filament is greater than 0.001 Ω/Ω-° C. and the resistance of the heating filament is proportional or inversely proportional to its temperature. By monitoring this resistance, the application of power to the heating filament may be regulated to prevent overheating of the heating filament. Calibration techniques are also disclosed whereby a memory containing encoded calibration information is disposed within or connected to a connector of the catheter. This memory may also include a program segment used by a cardiac output computer having a cardiac output calculation program, whereby the portion of code stored in the memory must be input into the cardiac output computer before the determination of the cardiac output can be performed. As a result of these improvements, the invention enables the thermodilution cardiac output calculation to be performed quite safely and accurately in a clinical setting.
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Citations
37 Claims
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1. A thermodilution catheter apparatus for making a thermodilution measurement, comprising:
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a flexible tubular catheter member adapted for introduction into a blood vessel of a patient, said catheter member having at least one lumen; a flexible heating filament disposed with respect to said catheter member so as not to touch the patient'"'"'s blood when said catheter member is inserted into a blood vessel, the heating filament capable of being heated to apply a predetermined quantity of heat to blood in said blood vessel; temperature detecting means for detecting downstream temperature variations of said blood as a result of the application of said predetermined quantity of heat to said blood; means for providing a thermodilution measurement based on the detected temperature variations; and wherein said heating filament can be slidably received into said at least one lumen. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A thermodilution catheter apparatus for making a thermodilution measurement, comprising:
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a flexible tubular catheter member adapted for introduction into a blood vessel of a patient, said catheter member having a one lumen; a flexible heating filament slidably receivable into said lumen of said catheter member for applying through said catheter member a predetermined quantity of heat to blood in said blood vessel; temperature detecting means for detecting downstream temperature variations of said blood as a result of the application of said predetermined quantity of heat to said blood; means for providing a thermodilution measurement based on the detected temperature variations. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of applying heat to blood in a blood vessel of a patient for a thermodilution measurement, comprising the steps of:
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inserting a flexible tubular catheter member into said blood vessel of said patient; slidably receiving a flexible heating filament through a lumen of said catheter member; applying power to said heating filament so as to generate a predetermined quantity of heat, whereby said predetermined quantity of heat is conducted through said catheter member into said blood. - View Dependent Claims (16, 17)
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18. A method of applying heat to blood in a blood vessel of a patient for a thermodilution measurement, comprising the steps of:
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inserting a flexible tubular catheter member into said blood vessel of said patient; slidably receiving a flexible heating filament through a lumen of said catheter member; applying power to said heating filament so as to generate a predetermined quantity of heat, whereby said predetermined quantity of heat is conducted through said catheter member into said blood; forming said heating filament from a material having a high temperature coefficient of resistance, wherein resistance of said heating filament is either proportional or inversely proportional to temperature and said heating filament has a low thermal capacitance and high thermal conductivity; and reducing power to said heating filament when resistance of said heating filament exceeds a predetermined resistance amount. - View Dependent Claims (19)
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20. A method of thermodilution measurement, comprising the steps of:
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inserting a flexible tubular catheter member into a blood vessel of a patient; slidably receiving a flexible heating filament through a lumen of said catheter member; applying power to said heating filament so as to generate a predetermined quantity of heat, whereby said predetermined quantity of heat is conducted through said catheter member into said blood; and detecting downstream temperature variations of said blood as a result of conduction of said predetermined quantity of heat into said blood. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. A method of applying heat to blood in a blood vessel of a patient for a thermodilution measurement, comprising the steps of:
slidably receiving a flexible heating filament through a lumen of a catheter member; and
applying power to said heating filament so as to generate a predetermined quantity of heat, whereby said predetermined quantity of heat is conducted through said catheter member into said blood when said catheter member is in said blood.- View Dependent Claims (28, 29, 30, 31, 32)
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33. A method of applying heat to blood in a blood vessel of a patient for a thermodilution measurement, comprising the steps of:
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slidably receiving a flexible heating filament through a lumen of a catheter member; and applying power to said heating filament so as to generate a predetermined quantity of heat, whereby said predetermined quantity of heat is conducted through said catheter member into said blood; and reducing power to said heating filament when said resistance of said heating filament exceeds a predetermined resistance amount. - View Dependent Claims (34)
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35. A method of applying heat to blood in a blood vessel of a patient for a thermodilution measurement, comprising the steps of:
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slidably receiving a flexible heating filament through a lumen of a catheter member; applying power to said heating filament so as to generate a predetermined quantity of heat, whereby said predetermined quantity of heat is conducted through said catheter member into said blood; and wherein said catheter is formed from a flexible material such that said catheter can be positioned in a patient to perform cardiac measurements. - View Dependent Claims (36, 37)
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Specification