Measuring Suite for Vascular Response Monitoring during Hyperbaric Oxygen Therapy by Means of Pulse Transit Time (PTT) Analysis

Figure 1. Diagram of the HBO therapy scheme TS 240-90 [3,4]. Air is defined as normal ambient air. Oxygen (O2) represents the administration of pure oxygen. The ordinate shows the pressure in atmospheres absolute, the abscissa shows the treatment time in minutes.

Figure 2. Graphical illustration of the Pulse Transit Time (PTT) using an electrocardiographic (above) and photoplethysmographic (below) signal.

Figure 3. 3D model of the 28 ×73 mm2 measuring unit PCB.

Figure 4. Housing of SPECTRE 3.0. (a) Exterior view of the device’s housing showing the assembled body and detachable lid and magnet holder. (b) Cross-section of the housing showing the placement of the PCB inside.

Figure 5. Wearable measuring unit with ECG electrodes, PPG finger sensor and a wrist strap. (a) Closed measuring unit with connected ECG electrodes and PPG sensor. (b) Measuring unit without the lid showing the battery connector’s accessibility. (c) SPECTRE 3.0 assembled on a person’s wrist, showing teh placement of the PPG finger sensor.

Figure 6. Overall system topology consisting of twelve SPECTRE 3.0 measuring units, one control unit, a router, and a data evaluating system running on a PC.

Figure 7. Systemsetup showing the control unit with touch display and graphical user interface, a router, and one SPECTRE 3.0 measuring unit.

Figure 8. Comparisonbetween standardized PQRST-complexes simulated by the phantom 320 ECG simulator and recorded simultaneously with both SPECTRE 3.0’s AFE4900 and a 12 bit-oscilloscope.

Figure 9. Raw (unfiltered) and digitally filtered ECG signal recorded with SPECTRE 3.0.

Figure 10. Digitally filtered PPG wave signal that was recorded with SPECTRE 3.0 and processed by the evaluation software.

Figure 11. Effects of nicotine on the PTT. The data set recorded with SPECTRE 3.0 shows the PTT and R-to-R interval (heart rate) progression over time. Nicotine intake starts at 300 s and ends at approximately 600 s.