Non-invasive Assessment of Inspiratory Effort and Tidal Distension During Non-invasive Ventilation (INSPIRE)

Airway pressure, flow, and esophageal pressure will be continuously recorded in all patients using a dedicated pneumotachograph and pressure transducer: all signals will be acquired and stored. Once a stable ventilation pattern is observed NIV will be administered by setting ventilator in invasive-pressure support ventilation. PEEP and PS-level will by kept constant while expiratory trigger will be adjusted to optimize patient-ventilatory synchrony. Immediately after, sudden end-inspiratory and end-expiratory occlusion maneuvers will be performed to measure plateau pressure and end-expiratory airway occlusion pressure (ΔPocc), respectively. Invasive PSV will be used only to perform the occlusion maneuvers, subsequently, PSV will be delivered in non-invasive PSV mode. Patient's blood-gas parameters and vital signs will be collected, including discomfort assessment. During the occlusion maneuvers, diaphragm ultrasound will be performed, and images will be recorded.