A novel technique to follow fast PaO2 variations during experimental CPR

An ultrafast responding fluorescent-quenching PO2 probe allows time-resolved, in vivo measurement of PO2. This study describes several validation experiments of this new device in vitro, and reports its first use during cardiopulmonary resuscitation in an animal model of cardiac arrest.

The influence of CO2, temperature and motion artefacts on the signal response of the PO2 probe was analysed in vitro by systematic variation of these values. Thereafter, with approval of the Review Board for the care and use of animals, CPR was performed in four pigs. The PaO2 course was recorded continuously at time resolution of <80 ms in the abdominal aorta using an uncoated fluorescence-quenching probe (Foxy AL-300, OceanOptics Inc., USA).

In vitro experiments showed that signal intensity is dependent on CO2 concentration (DeltaPfaO2=4 mmHg/vol.% CO2) and temperature (DeltaPfaO2=16 mmHg/ degrees C), but it is robust with regards to probe motion. In the animal experiments, the uncoated fluorescence-quenching probe was calibrated by repeated simultaneous measurements with the Paratrend 7 sensor to correct the PfaO2 for a potential signal drift, PCO2 and temperature variations. In all animal experiments, the individual PaO2 courses were clearly related to therapeutic interventions and their haemodynamic effects during CPR and allowed recording of ultrafast PO2 changes with a time resolution of 80 ms.

The results demonstrate the feasibility of ultrafast PO2 measurement during CPR and low-flow states. They also demonstrate very rapid systemic effects of CPR upon aortic PO2. Among many other useful applications, the information derived from this technique may help to define the optimum conditions for successful defibrillation and restoration of spontaneous circulation.