Transpulmonary Pressure - Guided Mechanical Ventilation in Morbidly Obese ARDS Patients: a Feasibility Study.

The goal of this clinical trial is to test a personalized intervention aiming to optimize the mechanical ventilator settings in morbidly obese patients suffering from moderate to severe Acute Respiratory Distress Syndrome (ARDS). The intervention consists of personalized measurements and calculations of the different pressures inside the thorax. The main question to answer is:

• Will the evaluated esophageal pressure-guided strategy lead to different mechanical ventilator settings than suggested by a strategy largely used in ARDS patients in France?

A specific nasogastric probe permitting to measure esophageal pressure will monitor participants. Esophageal pressure will act as an indicator of the pleural pressure. Other respiratory signals displayed by the mechanical ventilators will also be acquired.

Further, ventilator settings will be adjusted to the evaluated esophageal pressure-guided strategy, with possible benefit of this personalized approach.

The goal of this clinical trial is to test a personalized intervention aiming to optimize the mechanical ventilator settings in morbidly obese patients suffering from moderate to severe Acute Respiratory Distress Syndrome (ARDS). Mechanical ventilation is the cornerstone of the ARDS symptomatic treatment. Individualization of mechanical ventilator settings could improve prognosis mainly by preventing or decreasing accumulation of fluid in the lung and hemodynamic impairment. It is likely that class III obesity ARDS patients (defined by body mass index (BMI) \> 40 kg/m2), could benefit from a highly personalized approach, based on esophageal pressure monitoring. These patients have significantly higher esophageal pressures, acting as an indicator of pleural pressure, than the general ARDS population, while these patients have rather normal mechanical characteristics of the chest wall. Such features could suggest innovative mechanical ventilator settings, by integrating esophageal pressures values, aiming to obtain a slightly positive transpulmonary pressure at the end of expiration.

The intervention consists of personalized measurements and calculations of the different pressures, including the esophageal one, inside the thorax.

The main question to answer is:

• Will the evaluated esophageal pressure-guided strategy lead to different mechanical ventilator settings, mainly the positive end-expiratory pressure (PEEP) setting, than suggested by a PEEP-strategy largely used in ARDS patients in France?

A specific nasogastric probe permitting to measure esophageal pressure will monitor participants. The second generation esogastric multifunction Nutrivent catheter (SIDAM, Mirandola, Italy) will be used. It allows both enteral nutrition of the patients and monitoring of esophageal and gastric pressures during several days. Esophageal pressure will act as an indicator of the pleural pressure. Other respiratory signals displayed by the mechanical ventilators will also be acquired, permitting to calculate the trans-pulmonary pressures.

Further, ventilator settings will be adjusted to the evaluated esophageal pressure-guided strategy, with possible benefits of this personalized approach. The main benefits for the research participants will be the application of highly personalized mechanical ventilator settings, aiming mainly to select the best PEEP setting with the goal of optimization of opening the lung while avoiding the respiratory and hemodynamic consequences of excessive lung inflation. Monitoring of the end-inspiratory transpulmonary pressures will help to prevent excessive lung inflation.

Eligibility Criteria:
Inclusion Criteria:

* Adult patient (aged 18 years or older)
* Class III morbid obesity (BMI \> 40 kg/m2)
* Moderate or severe ARDS criteria (according to the Berlin definition)
* Less than 72 hours between fulfilling moderate or severe ARDS criteria and inclusion
* Tracheal intubation and invasive mechanical ventilation
* Informed consent (patient, next of kin), with possibility of an emergency procedure with deferred consent
* Covid-19 and non-Covid-19 patients

Exclusion Criteria:

* Contra-indication to nasogastric tube (uncontrolled coagulopathy, severe thrombocytopenia, nasal trauma, esophageal varices)
* Order to limit life-sustaining therapy
* ExtraCorporal Membrane Oxygenation (ECMO) in use
* Invasive mechanical ventilation \> 96 hours
* Elevated intracranial pressure
* Active air-leak: pneumothorax, pneumomediastinum
* Pregnancy or breast feeding
* Patient on state medical aid