Having said that, we did not find a marked difference

in measured PO2PO2 in the AL300 sensor, when we compared values calculated from fluorescence intensity (data not shown) with values from fluorescence quenching time constant measurements. This result was most likely observed because our two calibration points (peak and trough) were exactly the values that we subsequently measured. It is unlikely that any values in between would be accurately calibrated, which highlights the fact that sensors based on intensity selleck chemical measurement need to be calibrated specifically for the ranges and conditions in which they are intended to be used. A second potential limitation of any intravascular oxygen sensing is that in vivo   sensors are prone to biofouling with adsorbed material such as fibrin or large drug discovery clots, which would impair the signal recorded by the sensor. This is a long recognised problem with intravascular sensors

( Severinghaus and Astrup, 1986). In this respect, all four of our in-house PMMA sensors remained free from clotting after continuous immersion in non-heparinised flowing blood for a period of 24 h (see Fig. 4). This lack of clotting on the surface of the PMMA sensor suggests that it would be capable of measuring PaO2PaO2 oscillations at least for a 24-h period, a much longer period than that considered in previous studies. Our results demonstrate that the commercial AL300 fibre optic oxygen sensor currently used in animal research has a relatively slow response time for the detection of rapid PaO2PaO2 oscillations, and would not be Clomifene accurate at varying levels of oxygen saturations or high RR. Furthermore, it is made with ruthenium, a toxic material that is reported to be unsafe in the clinical setting (Yasbin et al., 1980). It is currently unknown whether the AL300 sensor is resistant to clotting when challenged with

continuous immersion in whole blood for a period of 24 h, hence it is unknown how immersion in blood for this duration of time may affect its performance. In contrast, the in-house PMMA sensor demonstrates that faster oxygen sensing technology is now available made of materials suitable for clinical application, and resistant to clotting for at least 24 h. The apparatus that we have described here is also suitable to be used with fast time response SaO2 sensors, if and when they are constructed, or with any other intravascular pH or CO2 sensor. The laboratory and animal work was supported by a Wellcome Trust Translation Award, Wellcome Trust, UK. We are grateful for the skilled technical assistance offered by our colleagues Jiri Chvojka, Jan Benes, Lenka Ledvinova, Vojtech Danihel at the Faculty of Medicine in Pilsen, Czech Republic, and by our colleagues Chris Salter and Alison Crossley at the Department of Materials, University of Oxford, United Kingdom.