Heated catheter for monitoring cardiac output

Details Heated catheter for monitoring cardiac output Heated catheter for monitoring cardiac output

1991-06-19

1994-01-11

Kamm, William E.

Surgery

Truss

Pad

128692, A61B 5028

Patent

active

052771911

ABSTRACT:
A heated catheter for monitoring cardiac output. Displaced from a distal end of a heated catheter (30) is a resistive heater (32) that heats blood flowing within a heart muscle (10). The resistive heater is mounted on the catheter so that when the catheter is inserted into the heart, the resistive heater is disposed in the right ventricle. A temperature sensor (34) is disposed downstream of the resistive heater, in or proximate the pulmonary artery during use. A differential amplifier (40, 70) provides an electrical current to the resistive heater that varies as a function of the difference between the temperature of the resistive heater, measured by a temperature sensor (35), and a predetermined temperature. In another embodiment of the invention, a resistive heater (90) has a resistance that varies with temperature. The resistive heater comprises one arm of a bridge circuit (85). A differential amplifier (110) provides an electrical current to the bridge circuit in response to the voltage developed across the bridge circuit. In yet another embodiment, a constant power dissipation is maintained in a resistive heater (60 ), so long as its temperature does not exceed a predetermined maximum. Should that occur, a power control block (80) incrementally reduces the power dissipated in the resistive heater, thereby insuring that the temperature of the resistive heater does not damage blood cells, yet is sufficient to provide a good signal-to-noise ratio in respect to a signal indicative of the temperature rise in blood flowing from the heart.

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A. L. Delaunois "Thermal method for continuous blood-velocity measurements in large blood vessels and cardiac-output determination" Mar. 1973, vol. 11 from Medical & Biological Engineering pp. 201-205.

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