Electrical Impedance Tomography Versus Computed Tomography in a Translational Pediatric Model: A Comparative Analysis on Distribution of Ventilation

Abstract

Background: Electrical impedance tomography (EIT) is a noninvasive, radiation-free, portable imaging modality that may be useful for the quantification of lung disorders and titration of mechanical ventilation. The principle of operation is based on changes in electrical conductivity that occurs as a function of changes in lung volume during ventilation. EIT offers potential important benefits over stand imaging modalities since the system is small, can be used at the bedside, non-radiologic and can be applied to patients for long periods of time. We aim to compare relationship between EIT and computed tomography (CT) methods of distribution of ventilation in a pediatric model.

Methods: We conducted experiments using 10 NZW rabbits and 3 Berkshire swine weighing 1.2-10.5 kg to help simulate a wide ranges of pediatric chest sizes of the newly developed, but not FDA-cleared Sentec LuMon EIT with neonatal and pediatric belt range. All animals were anesthetized, mechanically ventilated, placed in the supine position and underwent 3 phases of study: 1) unilateral lung ventilation by right or left mainstem intubation, 2) overdistension by incremental PEEP exposure in the normal lung prior to injury, and 3) atelectasis and reversal of atelectasis following surfactant washout injury followed by incremental and decremental PEEP exposure. The three phases resulted in 13-15 data collection of EIT and CT images per animal. Identical breaths were selected, and corresponding quadrants and layers mean lung impedance (EIT) and Houndsfield units (CT) percent of total change were compared during PEEP titration events.

Results: To date we have processed and compared 81 EIT to CT ventral images. There is good correlation (R² 0.9819) and no statistic difference in mean % change between imaging techniques. The mean % change during PEEP increment and decrement were 32.4% (± 47.9) and 36.3% (± 47.9) change for CT and EIT respectfully.

Conclusions: There is good correlation and no significant difference in % changes of ventilation in the ventral regions of the lung during PEEP titration between EIT and CT imaging techniques. We will continue to explore the other regions of the lung for comparison to identify similarities and differences between the two lung imaging techniques.

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