Regional Diaphragmatic Synchrony Index for Predicting Weaning Outcomes During Pressure Support Ventilation Spontaneous Breathing Trials

The primary aim of this study is to evaluate the predictive value of the inspiratory regional diaphragmatic synchrony index (RDSI-insp) during PSV-SBT for first-attempt weaning failure. Secondary objectives include: (1) assessing the correlation between RDSI-insp and conventional respiratory mechanics and diaphragmatic ultrasound parameters such as RSBI, MIP/NIF, VC, CPF, P0.1, DE, and DTF; (2) comparing differences in RDSI and DPSI between successful and failed weaning groups during inspiration, end-inspiration, and expiration; (3) exploring the association of anterior diaphragmatic dyssynchrony index, posterior/crural dyssynchrony index, and regional time-to-peak dispersion with weaning outcomes; and (4) evaluating the feasibility, analyzable image rate, and repeatability of diaphragmatic speckle-tracking and RDSI calculation in patients undergoing PSV-SBT.

Inclusion Criteria: * Age: Age ≥ 18 years. * Mechanical Ventilation Duration: Receiving invasive mechanical ventilation for ≥ 24 hours. * Weaning Readiness: The attending physician has determined that the patient meets the criteria for weaning assessment and plans to conduct a Spontaneous Breathing Trial (SBT) under Pressure Support Ventilation (PSV) mode. * Hemodynamic Stability: Hemodynamically stable prior to the SBT, defined as a mean arterial pressure (MAP) ≥ 65 mmHg, or requiring only low-dose vasopressor support. * Oxygenation Criteria: Oxygenation status permits an SBT, typically defined as FiO2 ≤ 0.60 and PEEP ≤ 10 cmH2O, or meeting the standard weaning assessment criteria of the participating institution. Exclusion Criteria: * Known or highly suspected phrenic nerve injury, or unilateral/bilateral diaphragmatic paralysis. * Neuromuscular diseases causing severely restricted spontaneous breathing capacity, as judged by the investigator to be unsuitable for RDSI analysis. * Recent chest or upper abdominal surgery, open trauma, skin infection, or extensive dressing coverage that prevents obtaining a reliable diaphragm ultrasound window. * Significant agitation or severe patient-ventilator asynchrony that prevents the acquisition of continuous and stable respiratory cycles. * Undrained pneumothorax, or conditions deemed unsuitable for ultrasound examination as judged by the attending physician. * Pregnant patients. * The patient or their legally authorized representative refuses to participate in the study.