Leakage current management systems, devices, and methods
A system and a method for reducing leakage current from a patient fluidly connected to a medical device by tubing filled with a conductive fluid, such as blood or dialysate, includes clamping a first current sensor onto the tubing, clamping a transducer that can induce a current in the tubing onto the tubing, and driving the transducer with an appropriate driving signal. The first current sensor detects the magnitude and phase of electrical current in the tubing, while the transducer is driven with a signal that induces an appropriate current in the tubing. The voltage in the tubing resulting from the induced current is at a level that causes the overall voltage drop from the patient to the medical device to be low enough that any leakage current due to this voltage drop is below an acceptable threshold for leakage current.
1 . A method of reducing an electrical leakage current flowing through a tube filled with blood, the method comprising:
providing a first current sensor configured to detect the electrical leakage current flowing through the tube filled with the blood at a first location along said tube;
providing a second current sensor configured to detect the electrical leakage current flowing through the tube filled with the blood at a third location along said tube;
connecting a patient to a dialysis treatment system with said tube, the tube conveying the blood between the patient and the dialysis treatment system;
providing a transducer configured to generate an electrical current in the tube filled with the blood at a second location along said tube;
providing a controller configured to receive as input a first signal from the first current sensor and a second signal from the second current sensor and to output a driving signal to the transducer;
detecting the electrical leakage current by the first current sensor and outputting the first signal from the first current sensor to the controller;
detecting the electrical leakage current by the second current sensor and outputting the second signal from the second current sensor to the controller;
receiving the first signal from the first current sensor and the second signal from the second current sensor by the controller;
generating the driving signal by the controller based on at least both of the first signal from the first current sensor and the second signal from the second current sensor; and
driving the transducer with the driving signal to thereby generate a canceling electrical current that reduces the electrical leakage current flowing through the tube filled with the blood between the patient and the dialysis treatment system,
wherein
the first location along said tube is closest to the patient,
the second location along said tube is between the first location and third location, and
the third location along said tube is farthest from the patient and closest to the dialysis treatment system.
2 . The method according to claim 1 , wherein
the first current sensor is clamped around the tube.
3 . The method according to claim 1 , wherein
the transducer is clamped around the tube.
4 . The method according to claim 1 , wherein
the second current sensor is clamped around the tube.
5 . The method according to claim 1 , wherein
the providing the transducer includes clamping the transducer around the tube,
the providing the first current sensor includes clamping the first current sensor around the tube, and
the providing the second current sensor includes clamping the second current sensor around the tube.
6 . The method according to claim 5 , wherein the generating the driving signal includes
setting a phase of the driving signal to match the phase of the electrical leakage current detected by the first current sensor; and
setting a magnitude of the driving signal to be below the magnitude of the detected electrical current.
7 . The method according to claim 6 , wherein
the step of setting the magnitude of the driving signal includes determining a difference between the magnitude of the driving signal and the magnitude of the detected electrical current, and the magnitude of the driving signal is selected such that the difference is a value based on an acceptable magnitude of a leakage current from the patient.
8 . A system for reducing electrical current flowing in a conductive fluid, the system comprising:
a tube with a conductive fluid that electrically couples a patient with a medical device, wherein the conductive fluid comprises blood;
a first current sensor clamped around the tube that measures a leakage current of the conductive fluid within the tube based on a magnetic field produced around the tube, wherein the first current sensor is located between the patient and a transducer;
a second current sensor clamped around the tube that measures a leakage current of the conductive fluid within the tube based on a magnetic field produced around the tube, wherein the second current sensor is located between the transducer and the medical device; and
a transducer clamped around the tube located between the first current sensor and the second current sensor, wherein
a transducer controller controls the transducer to inject canceling current into the conductive fluid within the tube based on leakage current sensed by the first current sensor and the second current sensor, the canceling current reducing the leakage current of the conductive fluid to a threshold level.
9 . The system of claim 8 , wherein the patient is electrified with a voltage level corresponding to a standard line voltage at a location of the system and the leakage current for the conductive fluid is substantially 80 μA when the transducer is not injecting canceling current into the conductive fluid.
10 . The system of claim 9 , wherein canceling current is at least 75 μA.
11 . The system of claim 8 , wherein the leakage current of the conductive fluid comprises alternating current.
12 . The system of claim 11 , wherein the current sensed by the first current sensor and the second current sensor is used by the transducer controller to adjust a phase of the canceling current injected by the transducer to be in phase with the leakage current in the conductive fluid.
13 . The system of claim 12 , wherein the canceling current has phase shift from the leakage current in the conductive fluid.
14 . The system of claim 8 , wherein the canceling current is injected using magnetic field energy generated by the transducer and the transducer controller.
15 . The system of claim 8 , wherein the first current sensor, the second current sensor, and the transducer comprise open spaces and the tube is positioned within the open spaces.
16 . The system of claim 8 , wherein the threshold level comprises a threshold range between 10 μA and 20 μA.