Abstract: A method and apparatus for performing electrical measurement of body mutual electrical impedances to determine changes in total body water in normal and deranged states of the body. The apparatus is particularly useful in determining the progression of dialysis cases during the period when renal dialysis is being performed on the patient. The method and apparatus utilizes a special electrical circuit for measuring electrical characteristics at selected body locations. Certain electrical characteristics are measured such as the resistance, the capacitive impedance, and the total reactance of the body, and the phase angle is calculated or measured. Utilizing some of these measurements, the total body water relative to the body weight may be determined.

Abstract: A leakage and continuity test unit for checking the ground impedance and leakage current in a medical instrument to ensure that the medical instrument is properly grounded and does not conduct an excessive amount of leakage current through the chassis. The unit includes a test probe which is interconnected with the equipment under test, the unit including a continuity circuit having a comparator which compares a fixed voltage with a voltage representative of the impedance to ground of the equipment under test. The output of the comparator is fed to a flip flop circuit which, when an excessive amount of ground impedance exists, drives a warning lamp circuit. If the impedance is below certain set limits, the flip flop will drive a lamp which indicates that the ground of the equipment under test is proper.

Abstract: A system for measuring the duration of the Achilles tendon reflex after the tendon has been tapped by a percussion hammer, the system including an input transducer which converts the reflex extension of the ankle joint to an electric signal which is fed to the input of an amplifier, the output of the amplifier being fed to a peak holder and to a comparator circuit. A portion of the signal from the peak holder is also fed to the comparator circuit which detects a crossover point of the two signals fed to the comparator. The first such crossover occurs during the hammer tap "artefact" and the second such crossover occurs during the relaxation phase of the reflex action. A timing device (such as an integrator) measures the time elapsed between the two crossovers and displays the result.