2. Department of Obstetrics/Gynecology, Urology, and Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA.
Background: The purpose of this study was to determine if ex vivo animal lungs could provide a method to investigate the etiology of ultrasonic B-lines ("lung comets"). B-lines are acoustic artifacts associated with the accumulation of extravascular lung water.
Methods: Transthoracic and epipleural sonograms were recorded in the endotracheally-intubated post mortem lapine and porcine lung specimens. Ultrasound imaging was performed using 6 MHz curved, 7.5 MHz or 14 MHz linear and 40 MHz transducers. To visualize subpleural gross pathomorphology, deep longitudinal cuts were made in the same areas of the lung that had been examined sonographically. Macroscopic digital photographs were obtained using gross specimen photography system.
Results: B-lines were detected within one hour after the animal's death and became dense and confluent in many areas within 2 to 6 hours. Florid pulmonary edema was evidenced by large amounts of pink frothy fluid in endotracheal tubes. Macroscopic crosssections revealed a subpleural mosaic of punctate red/purple hemorrhagic "microlesions" in the areas where B-lines were detected. Epipleural high frequency (40 MHz), three-dimensional (3D) ultrasound displayed B-lines as very dense, vertical, "stalactite"- like structures trailing down from the pleural surface. In the horizontal (transverse) plane B-line cross sections had oval shapes which were approximated by the Image J computational program to an ellipse with the major and the minor axes. The mean diameter of fifty two B-lines in one selected slice was 0.54 ± 0.2 mm (major axis) and 0.25 ± 0.08 mm (minor axis).
Conclusions: Ex vivo lung is a convenient and affordable model to study the mechanisms of B-line generation. The ex vivo model is stable enough to allow serial sonograms and monitoring of the lung epipleural and subpleural pathomorphology over several hours after the animal's death. High frequency 3D sonography may be a technology of choice to elucidate the etiology of B-lines.
Keywords: Lung ultrasound, B-lines, extravascular lung water, pulmonary edema, high-frequency three-dimensional ultrasound