Abstract:

The availability of wearable medical devices on the market is rapidly increasing, con- firming the trend towards unobtrusive wearable home-care, but bulky and obtrusive cardiorespiratory monitoring is still the gold standard. A possible explanation could be the lack of knowledge regarding the best placement on the body of new multimodal sensor patches. This research project aims to participate in the field of multimodal wearable monitoring devices by targeting this lack of knowledge regarding their optimal placement on the body. Therefore the best position for each measured signal in terms of signal quality is assessed. The studied signals are ECG, IP, and heart and lung sounds. This project proposes a performance mapping of the upper body through a conducted study based on a sensor patch prototype designed by the TU Berlin EMSP team. A study including fifteen subjects and comparing nine upper body patch positions has been done. The influence of movement on all signals measured by the patch device has also been studied. Six minutes of data have been retrieved for each position, meaning a total of 54 minutes raw data per subject. The quality of each signal at each position and for phases with and without movement has then been quantified via defined performance metrics. Their condensation to one metric per signal then enabled a first verdict about the optimal positioning for each assessed biosignal. It has been found that the ECG signal performed best on the lower left sternal border in all cases, while the IP’s maximum quality was reached between the 1st and 2nd ICS near the right midclavicular line without movement and on the least impacted position in the presence of movement. The stethoscope best detected heart sounds in the direct heart proximity, and respiratory sounds were best monitored on the upper right part of the chest. The IMU signals were all best on the lower chest positions in the presence of movement, as these positions are the least affected. Without movement, heart sounds could best be measured on the left side either directly near the heart (AccZ and GyrY) or at a lower point (GyrX), while the respiratory vibrations were best detected on the sternum for the AccZ and on the right and left lower chest for the GyrX and GyrY signals respectively. The found results mean that there is no universal best position for all measured signals, but that the placement of such patch devices should be application-specific by determining the most important signals in each case.