A total of four fibre optic sensors were tested: one sensor was deployed in a femoral
artery and one in an ear check details vein in each of the two animals, to gather evidence of clot formation or other fouling. The animals were part of a separate study being performed at Charles University, Plzen, and the insertion and presence of the fibre optic sensors did not compromise those studies in any way. After intravascular deployment for 24 h, the sensors were removed, stored in a plastic tube and returned to Oxford for analysis. Each sensor was examined by scanning electron microscopy (SEM) in Oxford, both in the unused state and after 24 h of continuous in vivo deployment. SEM Energy Dispersive X-ray (EDX) analysis was performed by means of a JEOL 6480 LV SEM equipped with an Oxford Instruments ABT-263 chemical structure X-MAX80 SD X-ray detector and INCA X-ray analysis system. The analysis was performed
using EDX, which investigates the characteristic X-rays produced by the interaction between the primary electron beam and the sample. The technique identifies all elements present with atomic numbers of 5 and greater (boron) with a detection limit of approximately 0.1 wt%. In this case the analysis was carried out in Low Vacuum mode with a gas pressure of 40 Pa (using air) to prevent charging on the uncoated samples. Differences between experimental ΔPaO2 values were assessed statistically using ANOVA, followed by post hoc comparisons between conditions (IBM SPSS Statistics for Windows, Version 20.0; Armonk, NY, USA). Statistical significance was assumed at values of p < 0.05. Variables are presented as
means ± SD, unless otherwise stated. A PMMA sensor was tested for its response to the simulated RRs, together with an AL300 commercial sensor, over a five-hour period, at 39 °C. Because the blood in the test rig was heparinised, there were no concerns about blood clots forming on the sensor surface. The in-house PMMA and AL300 sensors were used to monitor continuous ΔPO2 oscillations of 45 kPa peak-to-peak amplitude, from 5 kPa to 50 kPa Edoxaban (37–375 mmHg) at simulated respiratory rates from 10 to 60 bpm, over the five-hour period. Sensor output recording were taken at 20 min and 5 h during the experiments. Fig. 1 shows PO2PO2 values recorded in vitro by both the PMMA and AL300 sensors in response to amplitude-stable PO2PO2 oscillations at six simulated RRs in flowing blood at 39 °C. These values were recorded approximately 20 min after the sensors were immersed in blood. The response of the PMMA sensor was always faster than that of the AL300 sensor, and this was evident for all simulated RRs.