Hardware setup for tetrapolar bioimpedance spectroscopy in bandages

Abstract

As the demographic change progresses, medical research begins to focus on geriatric diseases. Our work concentrates on patients who suffer from age-related weakness of connective tissues or dilated venous valves which result in chronic venous insufficiency (CVI). CVI leads to a reduced perfusion of limbs, increased venous pressure and tissue deficiency, especially in the lower leg. As a result, chronic wounds develop that can persist for several decades. In clinical practice, CVI patients with wounds are outpatients who consult a physician for diagnosis every two months. A possible way to improve the interval of diagnosis are monitoring technologies like bioimpedance spectroscopy (BIS), which is capable to detect changes in tissue integrity. Developing a device for BIS in bandages could therefore enable quasi-continuous wound status monitoring and alert the physician if necessary. The presented hardware setup for BIS includes textile based electrodes for tetrapolar measurements that can be integrated into a bandage without reducing the comfort of the patient. Shape and size of the electrodes correspond to those of typical wound dressings. The hardware is based on the device AFE4300 for low energy consumption in place of highly dynamic or continuous measurements, as wound status dynamics are slow. We show that the complex impedance of human tissue can be measured with high precision if the electrodes were covered with compression stockings, as contact pressure enhances electrode-skin response.