Patent ID: 8774907

Claim:
A method of determining a location of a tip of a central venous catheter having a lumen filled with an electrolytic material, a portion disposed inside the superior vena cava, a second electrode attached to the skin of a subject, and a first electrode in communication with the electrolytic material, the tip having an opening in communication with the lumen that exposes the electrolytic material inside the lumen to the electrical environment outside the tip, the method comprising: obtaining a reference electrical signal comprising the voltage difference between the first electrode and the second electrode; generating a reference P wave from the reference electrical signal; determining a reference deflection value of the reference P wave; after the tip of the central venous catheter has been moved to a new position, obtaining a new electrical signal comprising the voltage difference between the first electrode and the second electrode; generating a new P wave from the new electrical signal; determining a new deflection value of the new P wave; calculating a ratio of the new deflection value to the reference deflection value; comparing the ratio to a threshold value; and indicating the tip should be withdrawn based on the comparison of the ratio to the threshold value.