This study proposes the End-expiratory Diaphragmatic Residual Contraction (EDRC) index to quantify residual diaphragmatic activity at end-expiration during Pressure Support Ventilation (PSV) mode. The study aims to validate the relationship between EDRC and dynamic intrinsic PEEP (PEEPi), triggering load, patient-ventilator asynchrony, and PEEP responsiveness through a brief, standardized PEEP titration trial conducted within a clinically safe range. This will provide a basis for subsequent individualized PEEP setting guided by EDRC.
Age ≥ 18 years. Patients receiving invasive mechanical ventilation in Pressure Support Ventilation (PSV) mode.
Pregnancy or lactation. Known esophageal diseases (e.g., esophageal varices, strictures, recent esophageal surgery) or contraindications to esophageal catheter placement.
The study population will consist of adult patients ($\\ge$ 18 years) admitted to the Intensive Care Unit (ICU) who are receiving invasive mechanical ventilation in Pressure Support Ventilation (PSV) mode. Participants will be recruited from the ICU at \[Insert Name of Hospital/Institution\]. The population is characterized by patients who are clinically assessed as having a risk of dynamic intrinsic PEEP (PEEPi,dyn) or are undergoing a spontaneous breathing trial (SBT) as part of the weaning process. All enrolled patients will have an indwelling esophageal balloon catheter placed for the measurement of esophageal pressure (Pes), which serves as the reference standard for respiratory mechanics. Patients will be screened for eligibility based on hemodynamic stability and the ability to tolerate the study procedures. Specific exclusion criteria include pregnancy, severe esophageal pathology, severe hypoxemia, and conditions precluding diaphragmatic ultrasound imaging (e.g., chest wall tra
Other
Prospective
Short-term PEEP Step Trial and EDRC Ultrasound Assessment
DeviceThis intervention involves a standardized, short-term PEEP step trial combined with a novel physiological assessment. During the trial, external PEEP is systematically adjusted in 2 cmH2O increments (Baseline, -2, +2, +4, +6 cmH2O) while maintaining stable Pressure Support Ventilation (PSV) settings. Simultaneously, the End-Expiratory Diaphragmatic Residual Contraction (EDRC) index is evaluated using diaphragm ultrasound speckle tracking. This distinguishes the intervention by providing a non-invasive, real-time quantification of residual diaphragmatic tension at end-expiration, which serves as a surrogate marker for dynamic intrinsic PEEP (PEEPi) and trigger load, distinguishing it from traditional static measurements or esophageal manometry alone.
Diagnostic Efficacy of EDRC-AUC for Identifying Clinically Significant Dynamic Intrinsic PEEP
The primary outcome is the diagnostic efficacy of the End-Expiratory Diaphragmatic Residual Contraction Area Under the Curve (EDRC-AUC) in identifying clinically significant dynamic intrinsic PEEP (PEEPi,dyn ≥ 5 cmH2O) in patients undergoing Pressure Support Ventilation (PSV). The diagnostic performance will be evaluated using Receiver Operating Characteristic (ROC) curve analysis, reporting the Area Under the Curve (AUC), optimal cut-off value, sensitivity, specificity, positive predictive value, and negative predictive value, with esophageal manometry and flow curves as the reference standard.
Correlation between EDRC-AUC and Respiratory Drive/Load Indices
To evaluate the correlation (using Pearson or Spearman correlation coefficients) between the End-Expiratory Diaphragmatic Residual Contraction Area Under the Curve (EDRC-AUC)
Incidence of Patient-Ventilator Asynchrony Events
To record and compare the total incidence and distribution of patient-ventilator asynchrony events across different PEEP levels. Specific events include:Ineffective triggering;Double triggering;Auto-triggering;Short or long cycling.
Agreement between EDRC-Guided PEEP and Esophageal Manometry-Guided PEEP
To compare the optimal PEEP level determined by the EDRC minimization principle with the optimal PEEP level determined by esophageal manometry (minimizing driving pressure or PTP). Bland-Altman analysis will be used to evaluate the mean bias and limits of agreement between the two methods.
Trends in Diaphragmatic Contraction Dynamics Across PEEP Levels
To observe and describe the dynamic trends of diaphragm thickening fraction (DTF) and the EDRC index across all phases of the PEEP step trial (Baseline, -2, +2, +4, +6 cmH2O), assessing the bidirectional effects of extrinsic PEEP on diaphragmatic load.
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