Shock wave damage from the ventral side in primary blast injury: An experimental study in pigs.

Aim/purpose: This study aimed to apply a shock wave from the ventral side of a pig and examine its effect to use the results for new body armor production for humans.

Methods: Seven male hybrid pigs were used. Each pig was placed under general anesthesia on the experimental table in a blast tube in the left lateral position to expose the front chest area, and shock waves generated by compressed air at 3.0 MPa were applied. We examined changes in vital signs and arterial blood gas in the hyper-acute phase and computed tomography (CT) images, and autopsies were performed for organ damage after 3 h of observation. Pathological examination was performed for lung damage, which is considered a characteristic of shock wave injury.

Results: All seven pigs survived. Respiratory arrest occurred in two pigs; however, spontaneous breathing resumed promptly afterward. Hypotension occurred at a frequency of 4. No bradycardia or cardiac arrest was observed in any pig. In the arterial blood gas analysis before and immediately after shock wave exposure and 1 h later, PaO2 decreased immediately but tended to improve thereafter. CT revealed pulmonary contusions and multiple bulla-like lesions on the surface of the lungs. An autopsy showed lung injury in all pigs, particularly in five cases with bulla-like lesions of various sizes on the lung surface across all lobes. Pathological findings showed visceral pleural detachment with elastic fibers from the lung parenchyma, and the cavity lesion on the lung surface comprised bullae. The degree of intra-abdominal hemorrhage varied; however, all but one case showed splenic injury.

Conclusion: None of the pigs exposed to shock waves from the ventral side died; however, most showed multiple bullae on the lung surface with lung contusion and splenic injury, which may have been greater than those exposed from the dorsal side. This may be due to the direct impact of the shock wave proceeding from the epigastrium and subcostal region, which are not protected by the skeletal structure of the thorax. These characteristics should be considered when producing new body armor for humans to protect the body from shock waves.