Method and apparatus for monitoring the fluid balance of the body

PCT No. PCT/SE83/00148 Sec. 371 Date Dec. 21, 1983 Sec. 102(e) Date Dec. 21, 1983 PCT Filed Apr. 20, 1983 PCT Pub. No. WO83/03746 PCT Pub. Date Nov. 10, 1983.The change in body fluid is monitored by placing a pair of electrodes at spaced locations on a body, i.e. a wrist and a diametrically opposed ankle and generating two high frequency alternating currents, one of 1.5 kHz and the other 150 kHz, through the body via the electrodes. Another pair of electrodes is placed in the current path of the first pair of electrodes and connected to a detector for measuring body impedances at the two frequencies. A microprocessor calculates the change in fluid weight of the body according to the empiric formula: where DELTA V=change in fluid weight k=a proportionality constant having a negative value S=body surface area, based on the patient's weight and length Z1 and Z2=impedance at the lower frequency (for example 1.5 kHz), and respectively, the higher frequency (for example 150 kHz) at the second measuring occasion Z1i and Z2i =corresponding impedances at the first measuring occasion (intitial values).