Catheter for measuring bioimpedance

Claim 1

An elongated, flexible catheter adapted to be inserted into a patient's esophagus for measuring the bioimpedance of a thoracic ssection thereof in order to determine the patient's cardiac output, the catheter having on the outer surface of a distal portion thereof a pair of axially spaced apart, cylindrically shaped sensing electrodes formed of conductive fabric, and a pair of axially spaced apart, cylindrically shaped transmitting electrodes, one of the transmitting electrodes disposed proximally to the pair of sensing electrodes and one of the transmitting electrodes disposed distally to the pair of sensing electrodes with axial spacing between each transmitting electrode and the adjacent sensing electrode being at least as great as the outer diameter of the catheter, the pair of transmitting electrodes being adapted to contact tissue on the inner wall of the patient's esophagus in order to apply high frequency electrical current to the thoracic section and the pair of sensing electrodes being adapted to contact tissue on the inner wall of the patient's esophagus in order to detect electrical signals therefrom which result from the application of high frequecy electrical current to the body section by the transmitting electrodes, the electrical signals sensed by the sensing electrodes being related to the bioimpedance of the thoracic section.