Implantable electrochemical sensor

Claim 1

A specific ion sensor for in vivo use which can be calibrated in situ without withdrawing blood from a patient which comprises a. an elongated insulated sensing electrode having an electrochemically active portion at one end exposed for contact with blood in a patient's blood vessel and having its other end exposed for connection to recording equipment, b. a guard tube receiving and enclosing a portion of the length of the sensing electrode removed from the electrochemically active portion thereof, c. a catheter receiving and enclosing a portion of the length of the tube and the sensing electrode and having an open leading end and additionally having a side port and having a trailing end through which the said other end of the sensing electrode extends, d. sensing electrode positioning means connected to the sensing electrode at a point removed from the electrochemically active portion for moving the electrode axially relative to the catheter to position the said active portion within the open end of the catheter for calibration purposes and to position said active portion outside the open end of the catheter for in vivo measurement purposes, e. drip line means communicating with the catheter through the side port for delivering electrolyte into the catheter at pressure greater than that of a patient's blood at the open end of the catheter, f. a reference electrode positioned partially in the drip line means for functional contact with electrolyte flowing to the catheter and having a portion disposed outside the drip line means for connection to recording equipment, g. flexible sealing means secured to the catheter between the side port and the trailing end of the catheter and pressure sealing against an annular portion of the tube to prevent electrolyte flow and blood reflux in the direction of the trailing end of the catheter beyond a predetermined point, and h. sealing means within the guard tube and in contact with an annular portion of the sensing electrode therein to prevent flow of electrolyte through the guard tube.