A new drip infusion monitoring system - biomed 2010

Biomed Sci Instrum. 2010;46:110-6.


A new drip infusion solution monitoring system has been developed for hospital and care facility use. The system detects and counts the fall of each drip chamber drop of fluid. Two non-contacting copper foil electrodes are used; one wrapped around the infusion supply polyvinyl-chloride tube under the solution bag and another around the drip chamber, forming two capacitors. Drip infusion fluids have electrical conductivity, so the capacitors are a series-connected electrical impedance. A thirty kHz sine wave is applied to the infusion tube electrode and the capacity-coupled signal on the drip chamber electrode is the transducer output. When an infusion fluid drop is forming, its diameter, and therefore drip chamber capacitance, are increasing, causing change in the output signal. When the drop reaches sufficient diameter to fall, the drip chamber capacitance decreases, which briefly returns the output signal to baseline. Therefore, the growth, fall, and drip rate of each drop of fluid can be detected from the output signal waveform. The system also has advantages of being insensitive to ambient light type and intensity, and detects when the infusion bag is empty.