SeisMote: A Multi-Sensor Wireless Platform for Cardiovascular Monitoring in Laboratory, Daily Life, and Telemedicine

Figure 1. Typical waveforms of the seismocardiogram (SCG) and photoplethysmogram (PPG) as compared with the electrocardiogram (ECG). (Upper Panel) ECG signal with indication of the Rpeak fiducial point used for the estimation of the pulse transit time (PTT). (Mid Panel) SCG signal with indication of the fiducial points associated with the Opening and Closing of the Aortic and Mitral valves (AO, AC, MO, and MC) to be considered for the estimation of the isovolumic contraction time (IVCT) and isovolumic relaxation time (IVRT), two clinical indexes of cardiac contractility and relaxation. (Lower Panel) PPG signal with indication of the timing for the PTT estimate.

Figure 2. The hardware components of the SeisMote platform. (a) The sensorized nodes allowing the measure of different combinations of signals; from left to right: ECG–PPG–SCG, ECG–SCG, SCG–PPG. (b) The USB dongle (the hub). (c) The wireless recharger. Inset: A detail of a node and the position of the LEDs, switching button, and PPG sensor.

Figure 3. Scheme of the node circuit. UI = User interface; SD = Secure Digital.

Figure 4. Diagram illustrating the TDMA (Time Domain Multiple Access) implementation and the data flow between the master (hub) and nodes at every connection event (CEn). Freq Hop = Frequency Hopping.

Figure 5. Diagram of the data fragmentation.

Figure 6. Scheme of the three monitoring modes.

Figure 7. Example of ECG, SCG, and PPG collected by a SeisMote node. Data were collected in the setting illustrated in Figure 9.

Figure 8. Relationship between application throughput and size of the application packet in a single node. The red spot indicates the application packet size selected for our protocol.

Figure 9. (a) Setting of the single node for the joint measurement of ECG, SCG, and PPG. This arrangement was used for the remote signal monitoring during the SideraB telerehabilitation program (see text). (b) Finger positioning for the PPG measurement.

Figure 10. Adapters for the PPG measurement at the forehead (A), fingertip (B), and earlobe (C).

Figure 11. Example of signals from the 4 node configuration of the system aimed at investigating the PTT in different arterial sites: finger (PTTf), earlobe (PTTe), and forehead (PTTfh) by a multisite measurement of PPG.

Figure 12. Example of signals from the 3 node configuration of the system aimed at investigating the SCG from different thorax sites (i.e., lower sternum, mitral, and aortic auscultation sites). Inset: positioning of the three nodes for the measure.