D1GIT: Automated, Temperature-calibrated Measurement of Capillary Refill Time

WINNER: 2nd Honorable Mention- Diagnostic Devices Category

The team has designed and prototyped an automated device to measure capillary refill time. The capillary refill test, used medically to test for shock and/or dehydration, is currently conducted manually: the practitioner depresses the patient’s finger for an arbitrary time with an arbitrary amount of force, relying on his/her own judgment to quantify the rate of returning blood flow. To address the need for a standardized capillary refill test, our device, the D1GIT, performs three main functions: standardizing the force applied to the patient’s finger, sensing the blood flow returning to the finger, and outputting a digital reading of temperature-adjusted capillary refill time. Prior art in this area has been limited to the development of sensing techniques that output a digital reading of refill time but still require unregulated manual application of force to the patient’s finger independent of the sensing setup. Therefore, the D1GIT is a novel device in that it is a compact solution for standardizing the capillary refill time test, incorporating and facilitating all of the actions of a human doctor. The D1GIT uses spatial calibration to transfer the same force (determined by doctor-patient testing) to each patient’s finger. An LED-phototransistor system measures the blood flow leaving and returning to the finger. Finally, a zener diode measures the temperature of the patient’s finger and adjusts the capillary refill time (CRT) accordingly. The D1GIT uses a 7-segment display to output both the nominal CRT and the temperature-adjusted CRT. All of these components are incorporated into a sleek outer casing, which is 3D-printed ABS plastic.