"International Consensus Reached on Recommendations for Lung Ventilation and Perfusion Assessment Using Electrical Impedance Tomography in Critically Ill Adult Patients"

Breath-Related Impedance Tomography is a non-invasive, radiation-free, bedside, real-time functional imaging technique for the lungs. It uses surface electrodes to monitor changes in lung tissue impedance, dynamically reflecting regional lung ventilation and perfusion—making it particularly well-suited for respiratory management in critically ill patients.

1. EIT Measurement Location Selection

Recommended electrode placement plane: The 4th to 5th intercostal space. When the recommended measurement plane cannot be reached, the 3rd to 4th intercostal space should be considered as the primary alternative. Electrodes must make direct contact with the skin, avoiding interference from dressings or catheters. During the examination, maintain consistent electrode positioning to facilitate accurate comparison of results across multiple tests. When comparing findings, also consider how body position and the measurement plane may influence the imaging results.

2. Electrode-Skin Contact in Obese Patients

Electrode gel, spray, or other solutions can be used to enhance the contact between the electrodes and the skin. During electrical impedance tomography recording, it’s important to avoid pressure changes from air mattresses that could interfere with electrode contact. Absolute impedance values—such as tidal impedance changes or end-expiratory lung impedance (EELI)—may not be comparable across different body positions, and variations in EIT parameters should not be interpreted solely as physiological effects. Obesity can influence the visualization of lung contours and areas in functional chest impedance tomography (EIT) images, but it does not affect the ability for continuous, dynamic monitoring.

3. Assessment of End-Expiratory Lung Volume and Tidal Volume

The absolute values of EELI cannot be compared across different subjects. If interruptions occur (e.g., measurements taken on different days; electrodes detached and reconnected), it becomes impossible to compare EELI changes across different measurements within the same individual. Changes in tidal volume impedance are closely associated with variations in tidal volume itself. Tidal volume impedance changes can be calibrated using actual tidal volumes to calculate the volume-impedance ratio. When positive end-expiratory pressure (PEEP) or body position is changed, the volume-to-impedance ratio may fluctuate. These changes can be particularly pronounced when electrode placement is suboptimal.

4. PEEP and Tidal Volume Titration

The regional respiratory compliance method (Costa method), used for end-expiratory positive pressure (PEEP) titration, calculates relative changes in compliance rather than absolute changes. “The 'optimal PEEP' can be defined based on the intersection of the relative overdistension curve and the relative collapse curve, depending on the patient’s specific needs and clinical objectives. The ‘optimal PEEP’ selected via the regional compliance method is influenced by the highest and lowest PEEP values during titration, the number of PEEP steps, the pressure difference between PEEP steps, and the duration at each PEEP level. EIT can be used to assess lung recruitability and the effectiveness of recruitment maneuvers.” 。

5. Contrast-enhanced EIT for Assessing Pulmonary Perfusion

Typically, 10-milliliter hypertonic (such as 5–10%) saline is used as the contrast agent. The contrast agent should be injected and EIT images acquired during an apnea period of at least 8 seconds. Individuals with spontaneous breathing may experience difficulty holding their breath, so careful interpretation is required. Technical specifications and analytical standards need to be standardized. 。

6. Identifying the Causes of Respiratory Failure

EIT helps identify localized ventilation abnormalities caused by various factors. Phase-inverted impedance changes were observed in the lung tissue of the dependent region, suggesting the possible presence of pleural effusion or diaphragmatic displacement within the measurement plane. By analyzing changes in expiratory flow or end-expiratory lung internal gas volume (EELI), EIT can help identify intrinsic PEEP or localized air trapping in obstructive lung diseases. Enhanced EIT using hypertonic saline infusion can detect localized perfusion defects caused by pulmonary embolism, as well as V/Q mismatches resulting from different underlying causes.

7. EIT-guided Mechanical Ventilation and Prognosis

Individualized ventilation strategies enabled by EIT technology hold promise for improving outcomes in patients with acute respiratory distress syndrome (ARDS), but further research is needed. EIT-guided PEEP outperforms fixed PEEP in improving oxygenation for surgical patients. 。

8. Respiratory Management and Treatment Assessment

EIT can be used to assess regional lung ventilation changes during spontaneous breathing trials, guiding weaning from mechanical ventilation. It can quantitatively assess the effects of the prone position on ventilation, perfusion, and V/Q matching. It can also evaluate the effectiveness of endotracheal suctioning. Furthermore, it detects the phenomenon of pendelluft and helps identify patients at risk of self-induced lung injury. Provides visual feedback for early mobilization, airway clearance, pulmonary physical therapy, and personalized rehabilitation in mechanically ventilated patients.

9. Ventilation and Perfusion Assessment During ECMO

EIT aids in the personalized setting of PEEP and tidal volume during veno-venous extracorporeal membrane oxygenation (V-V ECMO) therapy. Meanwhile, further validation is still needed for contrast-enhanced EIT to assess pulmonary perfusion in both veno-venous and veno-arterial extracorporeal membrane oxygenation (V-V/V-A ECMO) treatments.

Strong Consensus: 15 Items (100% Expert Agreement)

Consensus: 70 guidelines (75%-95% of experts agree)

No consensus reached: 2 items RVD ratio and non-invasive pulsatile blood perfusion ）

The consensus is based on 242 studies, covering research data from 1990 to March 2024. The evidence is primarily classified as Grade B (moderate level), suggesting that further high-quality research will still be needed in the future.

This consensus represents the most significant international guideline in the EIT field since the 2017 TREND Consensus. It not only updates the standards for technical procedures and data analysis but also clearly defines the core value of EIT in personalized respiratory management for critically ill patients:

Real-time visualization of lung ventilation and perfusion

Dynamic identification of pulmonary heterogeneity and abnormal regions

Guiding mechanical ventilation parameter settings and weaning process

Auxiliary diagnosis of the causes of complex respiratory failure

EIT is gradually becoming an indispensable bedside imaging tool in critical care medicine. The release of this consensus provides ICU physicians, respiratory therapists, and researchers worldwide with a standardized, evidence-based framework for operation and interpretation, helping to bridge the gap between EIT research and routine clinical practice. We look forward to the initiation of more high-quality clinical studies, collectively advancing pulmonary function monitoring technologies to benefit critically ill patients around the globe.