Patent ID: 7228170

Claim:
A device for monitoring hydration status in a hemodialysis patient comprising: a digital signal processor; an electrical output means being in electrical communication with the digital signal processor and being attachable to a body segment, the electrical output means being adapted to apply electrical current to the body segment; an electrical input means being in electrical communication with the digital signal processor and being attachable to a body segment, the electrical input means being adapted to receive the current transmitted through the body segment and transmit the same to the digital signal processor; and a microprocessor being in electrical communication with the digital signal processor; wherein the microprocessor is adapted to determine a relative change in extracellular volume in the body segment based on a change in resistance in the body segment, and to plot said relative change as a function of time ; and wherein the microprocessor determines the relative change in extracellular volume in the body segment according to the following equation: δ= ECV t /ECV 0 =(ρ× L 2 /R t )/(ρ× L 2 /R 0 )= R 0 /R t wherein δ is the relative change in extracellular volume in the body segment, ECV t is a variable equal to the resistivity (ρ) times the square of the length of the body segment (L) divided by the resistance (R t ) during hemodialysis, and ECV 0 is a constant value equal to the resistivity (ρ) times the square of the length of the body segment (L) divided by the resistance (R 0 ) at the beginning of dialysis.