The goal of this observational study is to evaluate whether the airway occlusion pressure recorded during a sudden end-expiratory breath-hold (ΔPocc) is correlated with esophageal swing in pressure and the reliability of P0.1, driving pressure, plateau pressure, pressure-muscle index, and diaphragm ultrasound as noninvasive estimates of inspiratory effort and lung distension in hypoxemic patients undergoing NIV.
The main questions this trial aims to answer are:
\- Primary Outcome: whether the airway occlusion pressure recorded during a sudden end-expiratory breath-hold (ΔPocc) is correlated with esophageal swing in pressure and the reliability of various noninvasive estimates of inspiratory effort and lung distension in hypoxemic patients undergoing NIV.
Secondary outcomes will include:
* Statistic metric of association between P0.1, ΔP, PMI and ΔPes
* Statistic metric of association between P0.1, ΔPocc, ΔP, PMI and PaO2/FiO2 ratio
* Statistic metric of association between P0.1, ΔPocc, ΔP, PMI and tidal volume
* Statistic metric of association between P0.1, ΔPocc, ΔP, PMI and DTF%
* Statistic metric of association between P0.1, ΔPocc, ΔP, PMI and Ex/DTF%
* Statistic metric of association between P0.1, ΔPocc, ΔP, PMI and respiratory rate, VAS dyspnea and VAS discomfort.
Participants will undergo the following tasks and treatments:
* Complete written informed consent before enrollment.
* Post-extubation noninvasive ventilation via nose-to-mouth and full-face masks.
* Monitoring of esophageal pressure (in all patients the catheter will be placed before extubation, according to clinical judgment, and its correct position will be verified through a positive pressure occlusion test)
* Continuous recording of airway pressure, flow, and esophageal pressure (Pes), using a dedicated pneumotachograph and pressure transducer.
* Sudden end-inspiratory and end-expiratory occlusion maneuvers, to measure plateau pressure (Pplat) and end-expiratory airway occlusion pressure (ΔPocc), respectively.
* Collection of hemodynamic and arterial blood-gas parameters, performed according to clinical judgment, along with assessments of dyspnea and discomfort using a modified visual analogue scale (VAS).
* Diaphragm ultrasound during occlusion maneuvers, measuring diaphragm displacement, diaphragm thickening fraction (DTF%), and diaphragmatic excursion (Ex) under various conditions.