Acute Respiratory Distress Syndrome (ARDS)
Conditions
Brief summary
Background: Electrical impedance tomography (EIT)-guided PEEP titration has been shown to improve regional ventilation distribution, increase respiratory system compliance, and reduce mechanical power in patients with acute respiratory distress syndrome (ARDS), but its effect on mortality remains unproven. In patients with moderate-to-severe ARDS, prone positioning for 4 hours allows pulmonary ventilation and perfusion to reach a new steady state, with optimization of ventilation-perfusion (V/Q) matching and other pulmonary physiological parameters. However, whether dynamic PEEP titration guided by EIT at this time point can further optimize V/Q matching and other pulmonary physiological parameters compared with conventional methods has not been reported. Objective: To investigate whether EIT-guided PEEP titration performed at 4 hours after prone positioning initiation can further optimize V/Q matching and other pulmonary physiological parameters in patients with moderate-to-severe ARDS undergoing prone positioning. Methods: This is a prospective, single-center, randomized, open-label, parallel-controlled physiological study. A total of 40 patients with moderate-to-severe ARDS (Berlin definition, PaO₂/FiO₂ \< 150 mmHg) will be enrolled and randomized in a 1:1 ratio to either the EIT-guided group or the control group. PEEP intervention will be performed at 4 hours after prone positioning initiation (T1) in both groups: the EIT group receives EIT-guided PEEP titration, while the control group receives PEEP set according to the ARDSNet/PEEP-FiO₂ table. The primary outcome is V/Q matching percentage assessed by EIT at 18 hours of prone positioning (T2) and 6 hours after supine repositioning (T3). Secondary outcomes include respiratory mechanics, EIT-derived parameters (regional ventilation distribution, global inhomogeneity index, center of ventilation), oxygenation indices, echocardiographic measures of cardiac function, and clinical outcomes (28-day mortality, ventilator-free days, ICU length of stay, etc.). Conclusion: This study will provide physiological evidence for early EIT-guided PEEP titration in patients with moderate-to-severe ARDS undergoing prone positioning, and will lay the foundation for future large-scale clinical trials.
Interventions
OTHEREIT-Guided PEEP Titration Group
PEEP titration is performed during mechanical ventilation to optimize respiratory mechanics and ventilation-perfusion matching in patients with ARDS.
OTHERARDSNet/PEEP-FiO₂ Table
PEEP will be set according to the ARDSNet/PEEP-FiO₂ table at 4 hours after prone positioning initiation (T1).
Sponsors
XIE MIN
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
SUPPORTIVE_CARE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 80 Years
Healthy volunteers
No
Inclusion criteria
1. Diagnosis of moderate-to-severe ARDS according to the Berlin definition, with a PaO₂/FiO₂ ratio \< 150 mmHg on optimal mechanical ventilation. 2. Clinical decision has been made to place a central venous catheter (internal jugular or subclavian vein) for clinical management.
Exclusion criteria
1. Pregnancy or postpartum state. 2. BMI \> 35 kg/m². 3. Duration of invasive mechanical ventilation \> 48 hours at enrollment. 4. Severe hemodynamic instability (mean arterial pressure \< 65 mmHg on norepinephrine ≥ 0.5 μg/kg/min). 5. Immediate need for veno-venous extracorporeal membrane oxygenation (VV-ECMO) at enrollment. 6. Contraindications to prone positioning or EIT monitoring, including but not limited to: facial or cervical trauma; unstable spinal, femoral, pelvic, or rib fractures; recent cardiac surgery; pneumothorax; elevated intracranial pressure; pacemaker or implantable cardioverter-defibrillator; severe chronic lung disease (e.g., severe COPD, asthma, interstitial lung disease); severe cardiac dysfunction (New York Heart Association Class III or IV, acute coronary syndrome, sustained ventricular tachyarrhythmia, or cardiogenic shock). 7. Lack of informed consent from legally authorized representative.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Ventilation-Perfusion (V/Q) Matching Percentage | At 18 hours of prone positioning (T2) and at 6 hours after supine repositioning (T3) | V/Q matching percentage assessed by electrical impedance tomography (EIT) using the EIT Evaluation Tool (SDMI) V2.7.1. V/Q matching reflects the efficiency of pulmonary gas exchange and is calculated from regional ventilation and perfusion distribution maps. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Respiratory System Compliance | Baseline, T2 (18h prone), and T3 (6h post-supine) | Respiratory system compliance (Crs) calculated as tidal volume divided by driving pressure (plateau pressure minus PEEP), measured under volume-controlled ventilation. |
| Driving Pressure | At baseline (T0), at 18 hours of prone positioning (T2), and at 6 hours after supine repositioning (T3) | Driving pressure (DP) calculated as plateau pressure (Pplat) minus PEEP, measured under volume-controlled ventilation. |
| EIT-Derived Regional Ventilation Distribution | At baseline (T0), at 18 hours of prone positioning (T2), and at 6 hours after supine repositioning (T3) | Regional ventilation distribution assessed by EIT, expressed as percentage of tidal impedance variation in four regions of interest (ROIs): ventral (ROI 1), mid-ventral (ROI 2), mid-dorsal (ROI 3), and dorsal (ROI 4), each corresponding to 25% of the anteroposterior diameter, Center of Ventilation (CoV), Global Inhomogeneity Index (GI), Shunt, Dead Space. |
| RVEDA/LVEDA | At baseline (T0) and at 6 hours after supine repositioning (T3) | Right Ventricular End-Diastolic Area to Left Ventricular End-Diastolic Area Ratio |
| RVFAC | Baseline and 6h post-supine repositioning (T3) | Right Ventricular Fractional Area Change（%） |
| TAPSE | Baseline and 6h post-supine repositioning (T3) | Tricuspid Annular Plane Systolic Excursion (mm) |
| TRVmax | Baseline and 6h post-supine repositioning (T3) | Maximal Tricuspid Regurgitation Velocity (m/s) |
| LVEF | At baseline (T0) and at 6 hours after supine repositioning (T3) | Left Ventricular Ejection Fraction（%） |
| SV | Baseline and 6h post-supine repositioning (T3) | Stroke Volume（ml） |
| CO | Baseline and 6h post-supine repositioning (T3) | Cardiac Output (L/min) |
| 28-Day Mortality | At 28 days after enrollment | All-cause mortality within 28 days after enrollment. |
| Ventilator-Free Days at 28 Days | At 28 days after enrollment | Number of days alive and free from invasive mechanical ventilation during the first 28 days after enrollment. |
| ICU Length of Stay | From enrollment through ICU discharge, assessed up to 28 days | Total duration of ICU stay (in days) from enrollment to ICU discharge or death. |
| Incidence of ECMO Use | During the ICU stay, assessed up to 28 days | Proportion of patients requiring veno-venous extracorporeal membrane oxygenation (VV-ECMO) during the ICU stay. |
| Incidence of Tracheostomy | During the ICU stay, assessed up to 28 days. | Proportion of patients undergoing tracheostomy during the ICU stay. |
Countries
China
Contacts
CONTACTMin Xie, MD, PhD
CONTACTJianmin Ling, MD
PRINCIPAL_INVESTIGATORMin Xie
Tongji Hospital
Outcome results
None listed