Bioimpedance for Healthcare and Lifestyle Applications

Willemijn Groenendaal
Imec The Netherlands/Holst Centre


Bioimpedance is a non-invasive technique with potential in many different healthcare and lifestyle applications. It is a measure of how well the body impedes electrical current, by using current injecting electrodes and sensing electrodes. The different tissues in the human body have different resistivity. In one type of bioimpedance measurement the frequency of the injected alternating current is constant. These types of measurements are ideal to follow changes in time, e.g., in respiration monitoring when bioimpedance changes as a consequence of airflow and chest movement. Respiration can be monitored with bioimpedance during walking, sitting and sleeping and can even be used to detect apneas during sleep. Combining single frequency bioimpedance measurements on the chest with electrocardiogram measurements enables hemodynamic monitoring. When adding electrodes to the bioimpedance measurement, one could sweep the current injection and sensing electrodes, a technique called electrical impedance tomography (EIT). This imaging technique allows continuous (and wearable) imaging of a selected 2D or 3D region, but with lower spatial resolution compared to high end imaging techniques like MRI or CT. EIT is most commonly used for ventilation monitoring. However, EIT has potential in lifestyle applications like hand gesture detection that could be used to interact with smartwatches. More possibilities of the technique are enabled by using multiple frequencies for the injected current. In that way body composition with respect to body water, fat content and musculature can be calculated. In heart failure patients this technique can be used to monitor pulmonary edema, while in hemodialysis patients it can be used to follow up on the treatment. Embodiments of the hardware are also very flexible, ranging from implantables, to wearables and clothing to non-contact embodiments like in a chair or a bed. Bioimpedance is thus a versatile technique that can contribute to unobtrusive patient and lifestyle monitoring.