Design and Validation of a Dynamic Digital Ruler for Hands-Free Chronic Wound Assessment

This paper documents the design and validation of a measurement tool for chronic wound assessment. Using the Google Glass™ head-mounted display (HMD) as a platform for research, we developed a digital ruler to dynamically capture wound dimensions in a hands-free manner. The system consists of the Glass HMD equipped with an infrared light emitting diode (IR-LED) distance sensor, lithium polymer battery, and a custom printed circuit board. Programmed using Android 4.4.2 (API 19), orthogonal rulers along the X and Y axes are superimposed on the Glass eyepiece and calibrated for measurement accuracy. To evaluate system performance, we conducted an ANOVA Gage Repeatability and Reproducibility (R&R) analysis with six wound care nurses measuring seven artificial wounds of various dimensions, two times each. Data was analyzed using Minitab statistical software. For width measurements, the results indicate that the total Gage R&R percent contribution was 10.2%, with 4.2% attributed to equipment variation (repeatability) and 6.0% to operator variation (reproducibility). Wound-to-wound variation was 89.8%. For length measurements, the total Gage R&R percent contribution was 16.7%, with 14.1% attributed to equipment variation and 2.6% to operator variation. Wound-to-wound length variation was 83.3%. The system received positive feedback from nurses as a hands-free measurement tool for sterile wound handling. Yet, further refinements are needed to improve system accuracy and depth measurement capabilities.