This is a monocentric, prospective, observational study that will be conducted in the general ICU of San Gerardo Hospital (Monza, Italy). Study protocol will be started when NMBAs infusion will be stopped for clinical reason until regain of spontaneous breathing activity.

Patients will be enrolled at the moment of NMBAs infusion interruption ("baseline" phase). Clinical data will be collected: hemodynamics, ventilation parameters and respiratory mechanics, arterial blood gas analysis, drugs used for sedation and their dosages. An EIT belt will be positioned around the patient's chest when clinical signs of spontaneous breathing activity will be detectable (unstable flow curve on the ventilator, deflection in airway pressure during an expiratory pause). In this phase ("NMBA interruption") same clinical data will be collected as at baseline. Patients will be ventilated in the same ventilation mode as before (Volume Controlled mechanical ventilation), but the inspiratory trigger on the ventilator will be turned on to reduce patient-ventilator asynchronies. When an EIT trace lasting at least 10 minutes will be recorded, an NMBA bolus (as prescribed by the treating physician) will be administered and a continuous infusion will be restarted. Clinical data will be collected again in this phase ("NMBA restart").

Inclusion Criteria:

• Patients with moderate-severe ARDS (according to Berlin definition)
• Patients treated with NMBAs
• age>18 years old

Exclusion Criteria:

• pregnancy,
• presence of air leaks (ex. presence of broncho-pleural fistula or pneumothorax)
• presence of contraindications to EIT belt positioning ( ex. presence of pace-makers, presence of unstable spinal fractures).

Patients with moderate-severe ARDS (according to Berlin definition) needing NMBAs administration will be included