Investigation of Impulse Oscillometry for the Detection of Extravasations using Design of Experiments and an Infusion Simulator.

Extravasation is a phenomenon that occurs when the infusion solution misses the vein and enters the surrounding tissue. We developed a sensor prototype utilising impulse oscillometry to detect extravasations at an early stage. A hydraulic impulse is injected into the infusion line to observe and analyse its progress. The aim of this study was to determine the tissue parameters that might influence the sensor measurement signal and signal changes during extravasation. We developed a simulator that simulates infusions and extravasations to test the prototype. Tissue-specific parameters can be adjusted independently. The effects of the tissue parameters, including blood pressure, blood flow, blood density, blood viscosity, vein diameter, venous wall thickness, and tissue modulus of elasticity, were investigated using the design of experiments method. The parameter values were varied between two levels and tested across 16 experiments. Blood pressure, blood viscosity, vein diameter, and venous compliance demonstrated the greatest impact on the sensor signal (p < .001). The other parameters showed negligible effects. Significant differences (p = .006) in the pressure signal of the sensor could be observed when the catheter changed from the venous position to the extravasal position.

Evaluation of Impulse-Oscillometric Extravasation Prevention.

Infusion liquid extravasation occurs in up to 6% of all intensive care patients and up to 78% for neonates. Currently, emerging extravasation cannot be detected. An impulse-oscillometric method to detect the onset of extravasation is tested and evaluated in vitro. A pinch valve compresses the infusion line, an impulse is formed, and the pressure response is recorded at the peripheral vein catheter. The response of this catheter-sensor-system is analysed by measuring the transient-step response (n = 10) for an opened and closed pinch valve. Trials utilising porcine shanks (n = 15) are performed with venous and extravasational catheter placement. The fundamental frequency, maximum amplitude, damping and decay constant of the pressure response are tested for differences between venous and extravasational placement. The response of the catheter-sensor-system shows no significant differences between an opened or closed pinch valve. The maximum amplitude, frequency, damping and decay constant of the pressure response differ highly significant for venous and extravasational catheter placement (p < .001). The parameters also differ depending on the presence of infusion liquid flow (p < .001). The method enables the detection of the onset of extravasation. Further tests are performed to investigate the relationships between impulse response and hydraulic impedance.