Electrical Impedance Tomography-Guided Identification of the Optimal Lateral Position in Postoperative ARDS
Effect of Left Lateral, Right Lateral, and Supine Positioning on Ventilation-Perfusion Matching Assessed by Electrical Impedance Tomography in Adult Postoperative Abdominal Surgery Patients With ARDS: A Prospective Randomized Crossover Physiological Study
Ruijin Hospital
22 participants
Jun 28, 2026
INTERVENTIONAL
Conditions
Summary
This prospective, randomized crossover physiological study evaluates the effects of lateral positioning (left lateral position and right lateral position) versus the supine position on ventilation-perfusion (V/Q) matching in adult postoperative abdominal surgery participants with acute respiratory distress syndrome (ARDS). Bedside electrical impedance tomography (EIT) will be used to quantify regional ventilation and perfusion (perfusion derived from an intravenous tracer bolus administered during a brief breath-hold) and to calculate global "normal V/Q" (normal V/Q, %). Oxygenation, respiratory mechanics (when applicable), and hemodynamics will be recorded concurrently. Feasibility and safety of the positioning protocol will also be assessed.
Eligibility
Inclusion Criteria5
- Age ≥18 years
- Postoperative abdominal surgery patients admitted to the ICU with ARDS (Berlin definition)
- Considered able to tolerate protocolized position changes by the treating team
- EIT belt placement and protocol procedures feasible
- Informed consent obtained from the patient or legally authorized representative
Exclusion Criteria6
- Contraindication to lateral positioning (e.g., unstable spine, uncontrolled bleeding, open abdomen, high-risk surgical wound condition)
- Severe hemodynamic instability or other conditions making participation unsafe
- High risk of airway/vascular line/drain dislodgement not manageable
- Pregnancy
- Refusal of informed consent
- Any other condition deemed inappropriate by investigators
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Interventions
Using a randomized crossover design, all subjects undergo three body position stages in random order. Each position (supine, left lateral, right lateral) is maintained for 60 minutes. Vital signs are stabilized per protocol, followed by EIT assessment of ventilation-perfusion matching. 1. Position stage duration: 60 minutes. 2. Stabilization period before measurement: 45 minutes after position change. 3. Washout: 45-minute supine washout period between position stages. 4. EIT ventilation measurement: after stabilization in each position. 5. EIT perfusion measurement: during breath-hold ≥8 seconds (actual breath-hold time recorded. 6. Tracer bolus: 10 mL of 10% sodium chloride solution OR 10 mL of 5% sodium bicarbonate solution, injected over 2-3 seconds via central or peripheral venous line.
Locations(1)
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NCT07669558