Electrical Characteristics of the Response Induced by Changes in Lactate Concentration

Interstitial lactate concentration Cl is a biomarker indicating the occurrence of early diabetic foot ulcers (DFUs). In this study, a certain concentration of lactate solution was added to a 0.9% N aCI solution to mimic interstitial lactate concentration changes, for which the response of the electrical characteristics to the Ci change was detected by using the electrochemical impedance spectroscope (EIS) method. EIS results show that the electrical impedance is sensitive to changes in Cl. The sensitivity of the electrical impedance to changes in Cl varies at different frequencies, with the maximum impedance difference ΔZ caused by Cl at the characteristic frequency fc = 1MHz. In order to detect the location of DFUs at early stage, electrical impedance tomography (EIT) is used to identify the location of Cl localized increase, which is the risk area of DFUs. The plantar sensors are arranged in a 4x4 array with 16 square electrodes located in DFU risk positions (forefoot and heel). EIT simulation results show that the best imaging performance with an image correlation coefficient (ICC) of 0.8789 at the square electrode with an edge length of 8 mm, when the electrode number 6 is used as the constant current excitation electrode. The results indicate that the EIT method adopted in this study demonstrates the capability of detecting regions of Cl change during the early stage of DFUs.