Patent ID: 8858455

Claim:
A method of locating a tip of a central venous catheter having a portion disposed within the superior vena cava, the catheter comprising a distal pair of electrodes and a proximal pair of electrodes spaced longitudinally from the distal pair of electrodes, the method comprising: obtaining a distal electrical signal from the distal pair of electrodes; generating a first P wave from the distal signal; determining a first deflection value of the first P wave; obtaining a proximal electrical signal from the proximal pair of electrodes; generating a second P wave from the proximal signal; determining a second deflection value of the second P wave; calculating a first ratio from the first and second deflection values; obtaining a superior vena cava deflection value; calculating a second ratio of one of the first deflection value and the second deflection value to the superior vena cava deflection value; and without advancing or withdrawing the tip of the central venous catheter, either determining that the tip of the central venous catheter is located in a desired location when the first ratio and second ratio are both approximately one, or that the tip of the central venous catheter has been inserted too far when the second ratio is greater than a maximum predefined threshold value, when the first ratio is greater than the maximum predefined threshold value, or when the first ratio is less than a minimum predefined threshold value.