Wearable bioimpedance for continuous and context-aware clinical monitoring

Bioimpedance monitoring provides a non-invasive,
safe and affordable opportunity to monitor total body water for a wide range of clinical applications. However, the measurement is susceptible to variations in posture and movement. Existing devices do not account for the variations and are therefore unsuitable to perform continuous measurements to depict trend changes. We developed a wearable bioimpedance monitoring system with embedded real-time posture detection using a distributed accelerometer network. We tested the device on 14 healthy volunteers following a standardized protocol of posture change and compared the obtained measurements with an existing commercial device. The impedance measured with both systems had a high correlation (r>0.98) and a Bland-Altman analysis revealed a bias of -4.5 and limits of agreement of -30 and 21. Context-awareness was achieved with processing accelerometer data placed at the upper and lower leg with an accuracy >95%. The calculated current consumption is as low as 10 mA during continuous measurement operation, suggesting that without recharge the system can be used for multiple days. The proposed motion-aware design will enable the measurement of relevant bioimpedance parameters continuously over long periods and aid in informed clinical decision making.