Lung-cOnservative Liquid VEntilation for the Induction of Ultra-Rapid COOLing After Cardiac Arrest

The "American Heart Association's 2022 Update" estimates that over 356,000 out-of-hospital cardiac arrests (OHCA) occur annually in the United States. These figures are consistant with data from European countries, where fewer than 10% of OHCA patients survive, despite 30% being successfully resuscitated before admission to intensive care units (ICU). The majority of these patients succumb to post-cardiac arrest syndrome (PCAS), a condition characterized by multi-organ failure.

To mitigate the severity of PCAS, current guidelines recommend continuous core temperature monitoring and active fever prevention through targeted temperature management (TTM) in patients who remain comatose following resuscitation from cardiac arrest. While TTM with a target temperature range of 32-36°C has been previously evaluated and applied in specific subpopulations, there is insufficient evidence to universally recommend one target temperature over another within this range. Conversely, experimental studies have demonstrated that the protective effects of therapeutic hypothermia (32-34°C) are strongly influenced by the rate of cooling initiated after resuscitation. These findings suggest that very early application of hypothermia may provide greater benefits compared to simply avoiding fever, emphasizing the importance of timely intervention.

In this context, Total Liquid Ventilation (TLV) with breathable liquids has been investigated in animal studies as a method to achieve ultra-rapid therapeutic hypothermia (URTH) following cardiac arrest. This innovative approach uses the lungs as a potent heat exchanger to achieve ultra-rapid cooling while preserving normal gas exchanges. TLV has demonstrated the capability to lower body core temperature from normothermia to the hypothermic range within 45 minutes, irrespective of body weight, in relevant experimental models. Furthermore, unlike earlier techniques of partial liquid ventilation, this method employs a lung-conservative liquid ventilation approach, which has been shown to be safe. The objective of the present OverCool study is to evaluate the performance and safety of the Vent2Cool device, designed to induce URTH by TLV safely following cardiac arrest.

Accordingly, OverCool is an open-label, single arm, non-comparative, multi-centric pilot study. The study primary objective is to demonstrate the ability of Vent2Cool to achieve a core body temperature of 33.0±0.5°C in less than 60 min after the start of the procedure in resuscitated patients admitted in the ICU after an intra- or extra-hospital cardiac arrest. The main secondary objectives are to demonstrate the safety of the procedure, the cooling performance, the ability to implement the procedure in the emergency setting of post-cardiac arrest management, the clinical outcomes and impact on biological markers.

Inclusion criteria

• Patient resuscitated after extra- or intra-hospital cardiac arrest, from presumed cardiac or asphyxial origin, regardless of the heart rate initially recorded.
• Age between 18 and 84 years old
• Time between collapse and return of spontaneous circulation (ROSC) < 60 min
• Presumption, at the time of inclusion, of a possibility of starting Vent2Cool within a period of less than 120 min after ROSC.
• Unconscious (GCS <8, not able to obey verbal commands after sustained ROSC)
• Patient affiliated with a social security system (If applicable)
• Consent of the member of patients' family or that of the trusted person if present and able to understand; otherwise certificate of emergency inclusion in compliance with applicable regulations.
• Vent2Cool must be connected to a standard cuffed ETT of 7.0 mm to 9.0 mm internal diameter for the procedure.

Exclusion criteria

• Conscious patient
• Patient Ideal Body Weight less than 40 kgs or more than 93 kgs
• Traumatic cardiac arrest, drowning, exsanguination, or sepsis
• Temperature at admission < 34.0°C
• Need for veno-arterial extracorporeal circulation (Extracorporeal membrane of oxygenation, ECMO) before return of spontaneous circulation (refractory cardiac arrest)
• One of the following signs at echocardiography at hospital admission:

• Acute cor pulmonale, defined by right ventricular enlargement with interventricular septal deviation, associated with a Tricuspid Annular Plane Systolic Excursion (TAPSE) < 12 mm and need for vasopressor agents
• Time-velocity integral of subaortic flow < 10 m/s
• Wrong positioning or damage of the endotracheal tube.
• Women under 50 years old (childbearing age) or for women of >50 years old, a positive pregnancy test (urinary) in case of pregnancy suspicion by the investigator. Possible breastfeeding during the study.
• Suspicion of intracranial bleeding
• History of severe Chronic Obstructive Pulmonary Disease (COPD) with long-term home oxygen therapy
• Acute respiratory pathology (pneumothorax, pleurisy, pneumonia, suspicion of contusion or intra-pulmonary hemorrhage following resuscitation)
• COVID-19 positive test in case of clinical suspicion and/or epidemic context
• Excessive mucus in the upper airways
• Patient presenting at least one of the following criteria in the mechanical ventilation parameters at inclusion:

• PEEP > 8 cm H2O
• Plateau pressure> 25 cmH2O
• Driving pressure> 15cmH2O
• Patient with at least one of the following criteria at inclusion:

• PaO2< 80 mmHg
• PaO2 / FiO2< 150 mmHg
• PaCO2> 48 mmHg