Lung ultrasound is a reliable method for evaluating extravascular lung water volume in rodents

Lung ultrasound (LUS) can diagnose extravacular lung water (EVLW) through the visualization of B lines in both humans and large animals. However, there are no published data on the use of ultrasound to detect EVLW in rats, the gold standard to evaluate of EVLW in rats is post-mortem gravimetric analysis. The present study was designed to determine the similarity between lung sonography and gravimetric measurements of EVLW in rats in an acute lung injury (ALI) model.

Thirty male Sprague-Dawley rats were randomized into control and experimental groups. The B lines were measured byLUS at baseline. ALI was induced by the intravenous administration of oleic acid (OA) at a dose of 9 ul/100 mg, and controls were injected the same amount of isotonic saline. After 1 h, B-lines were measured by LUS in each rat following the induction of ALI. At the end of each experiment, both lungs were dissected, weighed and dried to determine wet/dry weight ratio according to the standard gravimetric methodology. Lung samples from three rats in each group were examined histologically.

B-lines were present in all rats from experimental group at 1 h point after OA injection. The statistical correlation between the two methods of assessing EVLW provided an r = 0.834 (p < 0.001). Repeatability studies of the LUS technique (Bland-Altman plots) showed good intra-observer and inter-observer reproducibility.

The data suggest that, in an experimental rat model of ALI, B lines score as assessed by LUS can provide an easy, semi-quantitative, noninvasive. Real-time index of EVLW which is strongly correlated to experimental gravimetric assessments.