Electrical impedance tomography is able to track changes in respiratory function in endotoxin‐challenged rodents

Background and objective:  In order to assess and optimize the effect of new therapies for acute lung injury (ALI) in rodent models, a monitoring technique that continuously assesses the functional state of the lung is mandatory. Electrical impedance tomography (EIT) has been suggested as a technique for quantifying lung inflammation in ALI. However, EIT has not been evaluated in a rodent model of ALI. Methods:  EIT measurements were compared in ventilated Sprague–Dawley rats (n = 14), randomly subjected to intratracheal administration of endotoxin (LPS) or saline (control). Lung mechanics, lung weight wet/dry ratio and inflammatory markers in bronchoalveolar lavage fluid were also evaluated. Results:  LPS caused a significant decrease in lung compliance and TLC as compared with control (−42.0%, P = 0.04, and −27.9%, P = 0.02, respectively). These changes were paralleled by differences in mean impedance changes as detected by EIT (Spearman's rank correlation coefficient: ρ = 0.66 and 0.73, respectively, P < 0.01). LPS increased the lung weight wet/dry ratio (6.35 ± 0.42 vs 5.15 ± 0.07, P = 0.003), and the bronchoalveolar lavage total WCC (8.96 ± 1.87 vs 1.16 ± 0.10 × 109/L, P = 0.002) as compared with control. The lung weight wet/dry ratio was inversely related to the mean impedance change (ρ = −0.76, P < 0.01). Conclusions:  This study has demonstrated for the first time that eight-electrode EIT readily tracks the inflammatory response of lung tissue in a rodent model of ALI. EIT may thus provide a promising, non-invasive technique for monitoring the time-course of ALI in rodent models, and for testing novel pharmacological strategies to counter it.