Describe the ventilation patterns, describe the evolution of ventilation over time and describe the safety data for two strategies of ventilation (volume or pression modes) during specialized cardiopulmonary resuscitation of pre-hospital cardiorespiratory arrest: an observational and multicentre study.

Out-of-hospital cardiac arrest is a real public health issue, whose annual incidence in Europe is 67 to 170 per 110,000 inhabitants, but whose survival remains extremely low, of the order of 4.6 to 8%. Rapid implementation of the survival chain and then specialized resuscitation is therefore essential. The recommendations of the 2020 American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care and the 2021 European Rescucitation Council Guidelines recently reaffirmed the quality criteria for cardiopulmonary resuscitation (CPR) basic. Thus, during this CPR, rescuers must perform optimal chest compressions, that is, at a depth of 5 cm without exceeding 6 cm and at a frequency of 100 to 120/min with the minimum interruption time. Decompression must also be of quality.

As regards the ventilation of cardiac arrest, areas of uncertainty persist. This can be done using a bag valve mask (BAVU) or a respirator, regardless of the environment. The oxygen inspired fraction (FiO2) should be as high as possible during CPR. In the case of specialized and medicalized CPR, artificial ventilation must be implemented as soon as possible. Once the orotracheal intubation is performed, the clinician must mechanically ventilate the patient at a frequency of 10 breaths per minute without interrupting chest compressions. A ventilation strategy with reduced tidal volume (6-7 mL.kg-1 weight predicted) is preferred, associated with a low positive tele-expiratory pressure (PEEP) of 0 to 5 cmH20. Despite these clear recommendations, a heterogeneity of ventilatory practices is observed.

Regarding specialized ventilator ventilation, different ventilatory strategies are available for the clinician, however the scientific literature remains poor on this subject, especially in terms of safety and effectiveness of these strategies. Volume-assisted ventilation (VAC) is the most frequently used ventilatory strategy in the world, with the theoretical advantage of controlling the volume delivered to the patient, without being able to guarantee the pressures. Other alternative modes regulated in pressure exist but have the disadvantage of not guaranteeing volumes and minute ventilation. Each of these strategies (volume or pressure mode) is used in common practice, often with a preference for this or that ventilatory technique depending on the center and the available equipment.

The investigators therefore consider it important to accurately assess the ventilatory performance of these two strategies throughout CPR.

To do this, the investigators will conduct an observational, multicentre study. This study will aim to describe the ventilation patterns, describe the evolution of ventilation over time and finally to describe the safety data, for these two strategies during specialized cardiopulmonary resuscitation of pre-hospital cardiorespiratory arrest.

Inclusion Criteria:

• Adult patients (age 18 or older)
• With out-of-hospital cardiorespiratory arrest
• For which specialized cardiopulmonary resuscitation is indicated and started
• Supported by the SMUR of the Angers University Hospital of Angers, the Necker-Enfants malades University Hospital, the Grenoble University Hospital and the hospital of Annecy-Genevois
• And for which invasive mechanical ventilation on Monnal T60 transport respirator is started

Exclusion Criteria:

• patients for whom it is decided not to perform invasive ventilation and
• Patients opposed to participating in research
• Patients with a limitation of active therapies
• Patients who are not members or beneficiaries of a social security scheme

The population studied is that of out-of-hospital cardiorespiratory arrests managed by the emergency medicine prehospital medical teams (SMUR) of the four inclusion centers and meeting the inclusion criteria.