A laboratory model for studying blast overpressure injury

Blast injury remains an important source of trauma in both civilian and military settings. We have studied a recently developed blast wave generator to evaluate its effectiveness for laboratory study of blast injury. In order to determine the reliability of the device and the pathology of the lesions caused by the short duration (0.5-1.0 msec), and high intensity (60-375 psi) pressure wave, laboratory rats were exposed to the pressure waves generated by the machine. The animals were divided into three groups: the first exposed to midthoracic blasts, the second to abdominal blasts, and a group of controls exposed to a gentle stream of gas. Group I showed gross and microscopic evidence of lung blast injury of "rib imprint" hemorrhages, intra-alveolar hemorrhage, marked increase in lung weight, prolonged apnea, and bradycardia. Group II showed typical blunt abdominal trauma at the closest ranges, but characteristic submucosal hemorrhages up to 4.0 cm from the blast nozzle. In both groups, a protective effect was seen in heavier animals. The blast wave generator permits reproducible blast injury in the laboratory that is safer and faster than current methods. The lung and bowel lesions induced are grossly and microscopically similar to injuries of blast exposure seen in clinical patients.