Electrical Impedance Tomography (EIT) is a non-invasive, radiation-free, bedside imaging technique that has been in clinical use for over three decades (1).

It is primarily utilized to monitor regional lung ventilation in mechanically ventilated patients. In recent years, EIT has become a routine tool in critical care settings due to its capacity to provide real-time, bedside insights into pulmonary function. Its applications are diverse, ranging from support during non-invasive ventilation and endotracheal intubation (2) to the management of complex cases of mechanical ventilation. One of its key advantages lies in guiding the optimization of Positive End-Expiratory Pressure (PEEP) titration, which may help tailor ventilatory support to individual patients and potentially reduce the mechanical power delivered to the lungs(3,4).

Despite these benefits, current evidence does not conclusively demonstrate a reduction in mortality associated with the use of EIT in critical care (5,6). Nevertheless, EIT shows promise in several emerging areas, such as monitoring ventilation distribution during prone positioning - even in awake, non-intubated patients (7) - and in the early detection of atelectasis under various clinical conditions (8).

Recently, advancements in EIT technology have led to the development of new models capable of assessing pulmonary "pulsatility," thereby expanding the potential clinical applications of EIT beyond traditional ventilation monitoring. This feature may facilitate the bedside detection of conditions such as atelectasis, pneumonia, pleural effusion, and even pulmonary embolism (9,10).

In this context, the Intensive Care Unit at Erasme Hospital is acquiring two EIT devices to enhance diagnostic capabilities and improve the care of patients requiring either non-invasive or invasive ventilation during their ICU stay. To support the systematic implementation of these devices and enable future research, it is necessary to establish a registry documenting their clinical use within the ICU. This registry will serve as a foundation for tracking usage patterns, evaluating outcomes, and potentially contributing to future scientific studies.

Standard ICU data such as SOFA scores and SAPS II will be recorded, as is already routinely done in some registries like Epimed.

This registry will be specific to the Erasme ICU and will collect detailed data on ventilation parameters, EIT measurements, and recruitment maneuvers in patients undergoing mechanical ventilation-whether invasive or non-invasive-when the clinical team determines that a recruitment maneuver is indicated and chooses to use an EIT device for monitoring.

Data will be entered into RedCap by the attending physicians or physiotherapists responsible for the patient.

Data collection will be prospective, as it is not technically possible to automatically synchronize the recording of ventilation parameters and EIT measurements using the existing software systems.

There are no expected risks for the patients, as the procedures involved are considered standard practice in intensive care settings.

Patients may benefit from the collection of these data, as it allows for closer monitoring of ventilation parameters during their ICU stay.

As this is a registry-based study, there will be no predefined duration or fixed number of patients. However, we estimate data will be recorded over a five-year period, with an inclusion of at least 300 patients per year.

Inclusion Criteria for ICU Patients:

• Patient aged more than 12 years old (no pediatric EIT belt)
• Patient monitored by an EIT belt OR Patient undergoing a recruitment maneuver OR Patient undergoing prone position.

Inclusion Criteria for ICU Patients:

• Patient aged more than 12 years old (no pediatric EIT belt)
• Patient monitored by an EIT belt

Exclusion criteria Patient who expressed opposition to participate.

All critical care patients for whom clinicians estimated the need for EIT measurements could be included, except pediatric patients under 12 years of age, as the belt used for this device is not designed for children.