Imbalances in regional lung ventilation: a validation study on electrical impedance tomography

Area of Science:

• Critical Care Medicine
• Medical Imaging
• Pulmonary Physiology

Background:

• Regional ventilation imbalances, characterized by gravity-dependent lung collapse and overdistention, are linked to ventilator-induced lung injury (VILI).
• Accurate monitoring of ventilation distribution is crucial for optimizing mechanical ventilation strategies and mitigating VILI.
• Electric impedance tomography (EIT) is an emerging imaging modality with the potential to assess regional ventilation in real-time.

Purpose of the Study:

• To validate the accuracy of EIT in measuring ventilation distribution.
• To compare EIT measurements with dynamic computerized tomography (CT) in critically ill patients.
• To assess the reproducibility and precision of EIT for monitoring ventilation.

Main Methods:

• Critically ill patients on mechanical ventilation underwent simultaneous slow-inflation breaths monitored by EIT and dynamic CT.
• Multiple scans were acquired for each patient, with EIT data collected over six repeated breaths.
• Analysis focused on agreement between EIT and CT in detecting right-left and gravitational ventilation imbalances.

Main Results:

• EIT demonstrated acceptable reproducibility over repeated breaths.
• There was good agreement between EIT and CT in detecting right-left ventilation imbalances (bias = 0%, limits of agreement = -10% to +10%).
• EIT precisely assessed relative ventilation distribution in thoracic layers and showed strong correlation with CT-derived absolute air content (r² ≥ 0.92).

Conclusions:

• EIT is a reliable tool for assessing regional ventilation distribution in mechanically ventilated patients.
• EIT measurements correlate well with dynamic CT, supporting its use in clinical settings.
• EIT can help identify ventilation imbalances, potentially guiding mechanical ventilation to reduce VILI.