Patent ID: 8388546

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, 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: attaching a second electrode to the skin of a subject, positioning the tip of the central venous catheter within the superior vena cava; while the tip is positioned within the superior vena cava, 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; one of advancing and withdrawing the tip of the central venous catheter to a new position; while the tip is in the 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 one of advancing or withdrawing the tip based on the comparison of the ratio to the threshold value.