Background During ventilatory assistance, optimization of settings is critical to allow a personalized support and avoid over- or under-assistance. But little data are available in clinical practice to guide the adjustment of the support. In adults, esophageal pressure (PES) has been shown to be a reliable surrogate of pleural pressure (PPL) and clinical studies suggest that PES may be useful to guide the management of mechanical ventilation. In children, the PES measurement could have similar potential benefits, but beforehand the reliability of PES to estimate PPL needs to be assessed.

Objective The primary objective of this study is to validate the reliability of PES directly monitored using a miniature catheter tip pressure transducer (Gaeltec® system) to estimate PPL, when compared to a gold standard, i.e the direct PPL measurement in situ.

Method This is a prospective single center study. Children <18 years old, hospitalized in the pediatric intensive care unit, requiring invasive ventilation and with at least one chest tube will be included.

Protocol A pressure transducer will be connected to the existing chest-tube and PES (measured by Gaeltec® and feeding tube), PPL, PAW, respiratory volume and flow will be simultaneously recorded.

Expected results We expect that the PES-based methods will provide an accurate estimation of PPL. Once this tool validated, PES could be helpful to optimize mechanical ventilation in children, and further interventional trials would be warranted to evaluate if its use could allow a reduction of the ventilation support duration.

Inclusion Criteria:

• Children <18 years old, hospitalized in the pediatric intensive care unit;
• Requiring invasive ventilation for more than 4 hours according to the prescription of the attending physician;
• With at least one chest tube.

Exclusion Criteria:

• Contraindications to the placement of a new nasogastric tube (e.g. bilateral phrenic paralysis, trauma or recent surgery in cervical or nasopharyngeal regions, severe coagulation disorder);
• Hemodynamic instability, as defined by the treating team, and the absence of recent (<4 hours) increase in the flow of dopamine, epinephrine, norepinephrine, or dobutamine;
• Respiratory instability defined as a severe respiratory failure requiring FiO2 > 60%, or PaCO2 > 80 mmHg on blood gas in the last hour;
• Persistent pleural effusion or pneumothorax despite the chest-tube;
• Bronchopleural fistula;
• Recent (<12 hours) thoracic hemorrhage;
• Delayed sternal closure at the time of study;
• Significant pericardial effusion;
• Absence of parental or tutor consent;
• Patient for whom a limitation of life support treatments is discussed or decided.