Portable measurement device to quantitatively measure capillary refilling time

Capillary refilling time (CRT) is defined as the time taken for the distal capillary bed to regain its color after the capillaries have been blanched through external skin compression. Measuring the CRT is a simple method of evaluating peripheral circulation in the clinic. Typically, the CRT is measured by manually recording the time taken for the skin color to be regained after blanching using a timer. However, this method is observer-dependent, which results in variability and subjectivity. In this study, a portable CRT measurement device was developed for simple quantitative measurement. This device standardizes the operator's manual compression by measuring the manual compression force using a force sensor and displaying it as well as the duration of the compression on a display unit. The device also measures CRT by recording the change in skin color after fingertip compression using an RGB color sensor. The stability of CRT measurement by this device was compared with that of conventional CRT measurement, which involves manual compression and naked eye observation. These results showed that CRT measurement using this device was more stable than that by the conventional method. The proposed device can potentially improve the reliability of CRT measurement by reducing the variability in the manual compression force and ensuring accurate recording of the time.