Patent ID: 11957890
Assignee: GAMBRO LUNDIA AB
Field: Medical technology (Instruments)
Classification: CPC A  H | IPC A

Claim 17:
18. A method for controlling leakage currents in a medical device, the medical device comprising:
at least one fluid circuit configured to be coupled to a vascular access of a patient to introduce a fluid into the patient, wherein the at least one fluid circuit comprises a heated portion;
a warming unit coupled to the heated portion to warm the fluid before the fluid passes to a blood circulation system of the patient;
wherein the warming unit comprises:
at least one electrical heater element connected to a main electrical source providing a mains voltage,
at least one heat transfer element in contact with the heated portion of the at least one fluid circuit of the medical device,
an electrical safety insulation interposed between the at least one electrical heater element and the at least one heat transfer element,
a ground connection connected to the at least one heat transfer element, and
a leakage current reduction circuit operatively interposed between the at least one heat transfer element and the ground connection;

wherein the method comprises:
keeping the leakage currents below a first limit value under normal working conditions of the warming unit in which the at least one electrical heater element is connected to the main electrical source to perform heating, and
keeping the leakage currents below a second limit value, higher than the first limit value, under a fault condition of the warming unit in which the patient is connected to the mains voltage;

wherein keeping the leakage currents below the first limit value comprises: connecting the main electrical source to the ground connection through a resistance element placed between the at least one heat transfer element and the ground connection; and
wherein keeping the leakage currents below the second limit value comprises: disconnecting the ground connection from the at least one heat transfer element, while keeping the at least one electrical heater element connected to the main electrical source to continue warming the fluid.