A new drip infusion solution monitoring system with a free-flow detection function

A new drip infusion solution monitoring system has been developed for hospital and care facility use. The system detects the fall of each drip chamber drop of fluid and also a free-flow situation. Three non-contacting copper foil electrodes are used. The electrodes are wrapped around the infusion supply polyvinyl chloride (PVC) tube from the solution bag, the drip chamber, and the infusion PVC tube from the drip chamber. Drip infusion fluids have electrical conductivity, so a capacitor is formed between the infusion fluid and each electrode. A thirty kHz sine wave is applied to the electrode wrapped around the infusion supply PVC tube from the solution bag. The capacity-coupled signal on the drip chamber electrode is the transducer output. When an infusion fluid drop is forming, its length and diameter, and therefore the drip chamber capacitance, are increasing, causing change in the output signal. The drip chamber electrode can detect the fall of each drip chamber drop of fluid. When the infusion solution becomes free-flow, an infusion fluid drop is not forming and the infusion fluid flows continuously. Therefore, the capacitance of the electrode around drip chamber does not change the output signal. On the other hand, the electrode wrapped around the infusion supply polyvinyl chloride tube under the drip chamber detects the thirty kHz sine wave conducted by the infusion fluid. The drip chamber electrodes and the infusion supply PVC tube under the drip chamber detect each drop of fluid and free-flow, respectively.