ORI to Reduce Hyperoxia After Out Hospital Cardiac Arrest

The investigator's research proposal is a randomized controlled study evaluating two different monitoring strategies to titrate FiO2 in order to rapidly and safely achieve optimal SatO2 targets during early ROSC of non-traumatic OHCA in adults.

Primary hypothesis:

Monitoring transport to hospital of sustained ROSC of OHCA patients using multiple wavelength detectors that allow ORI continuous measurement will reduce hyperoxia and hypoxia burden associated with transport.

Secondary hypothesis:

Multiple wavelength detectors allowing ORI continuous measurement will reduce hyperoxia at ER admission as measured via blood gas analysis.

Tertiary study hypothesis:

Multiple wavelength detectors allowing ORI continuous measurement will reduce reperfusion neuronal injury measured through NSE levels at 48h post ROSC

Oxygen has a pivotal role in emergency medicine as a lifesaving therapy in numerous situations. In order to avoid hypoxia-related morbidity and mortality, oxygen is delivered in emergencies in a liberal way, even when hypoxia is not confirmed. Nevertheless, as every medication, experimental and clinical studies have highlighted potential side effects of high oxygen tension that could worsen outcome. Cardiac arrest is the archetypal situation given the urgent need of rapid oxygen delivery to organs. However, this global ischemia-reperfusion syndrome produces high amounts ROS that could magnify the damages of the ischemic period and might be significantly increased by high oxygen tension. Thus, hyperoxia in the post-resuscitation context of cardiac arrest is an important topic. Advances in noninvasive oxygen monitoring can now allow for non-invasive monitoring of hyperoxia in pre-hospital settings. So far, despite the recognized urgent need for advancements in the management of oxygen delivery during early ROSC, studies have been exclusively retrospective and interventional studies failed to safely titrate oxygen in the prehospital context possibly due to lack of technological support7. The aim of investigator's is therefore to determine whether technological advances can allow for a safer and more accurate delivery of oxygen in the early ROSC of OHCA, reducing ROS damage. Further research should then, if our hypothesis would be confirmed, reproduce the data in different settings and further investigate whether better oxygen administration during early ROSC improves patients' outcome.

Patient showing a sustained ROSC after an OHCA will be monitored according to current hospital protocols during pre-hospital transport. In addition to traditional monitoring patients will all be monitored with a Masimo device allowing continuous non-invasive measurement of ORI. Patients will be randomly assigned to blinded measurement of ORI (not allowing the clinician to visualize collected information through additional monitoring) or bi-modal monitoring (allowing the clinician to gather information both form traditional monitoring and from additional monitoring showing ORI values). In the latter case clinicians participant will be encouraged to target an ORI lower than 0.5 together with a SatO2\>91%. In case of blinded measurement of ORI clinicians will manage ventilation according to standard SatO2 targets (94-98%). Ventilator settings in both groups will be managed in order to target an end-tidal CO2 (ETCO2) between 35 and 45mmHg.

An arterial blood sample and a central body temperature will be taken at hospital admission.

The arterial blood sample will be analysed for glucose, pH, PaCO2 and PaO2 and corrected for temperature in order to calculate dissolved oxygen.

A second blood sample will be done at 48h to measure NSE. A standardised form will be filled by the pre-hospital physician participant gathering information about no flow time, low flow time, first assessed rhythm, BMI, smoking habit and patient demographics.

Eligibility Criteria:
Inclusion Criteria:

* out hospital cardiac arrest
* non traumatic etiology
* ROSC achieved

Exclusion Criteria:

* less 18 year
* traumatic etiology
* prisonnier
* pregnant woman