Efficacy of Body Armor in Protection against Blast Injuries using a Swine Model in a Confined Space with a Blast Tube

Background: Regarding blast injuries, fatal damage leading to immediate death is considered due to shock-lung, respiratory arrest, or circulatory failure induced by a neurological reflex, such as the severe vagal nerve reflex. It has not yet been determined whether a bulletproof vest protects against or aggravates shock-lung or the neurological reflexes considered to be fatal in the super-acute phase after an explosion. Purpose The purpose of this study was to clarify whether a bulletproof vest would protect the body in a pig blast model using a blast tube built at National Defense Medical College, which is the first such blast tube in Japan. Methods Seventeen pigs were divided into two groups: the body armor group (n = 6) and the non-body armor group (n = 11). Pigs underwent tracheal intubation with IV and A lines were secured to measure vital signs were checked and collect blood samples. Then, under intravenous anesthesia, the pigs were tightly fixed in the left lateral position on a table and exposed from the back neck to the upper lumbar back to the blast wave and wind with or without body armor, with the driving pressure of the blast tube set to 3.0 MPa. We checked the vital signs, collected blood samples, and observed the pigs for 3 hours after injury. Results When the surviving and dead pigs were compared, blood gas analyses revealed significant differences in PaO2, PaCO2, and pH in the super-early phase. In addition, all pigs injured by the blast wave and wind had lung hemorrhage, and 14 of 17 pigs had intra-abdominal hemorrhage with splenic injury. All 6 animals in the body armor group and 6 of the 11 animals in the control group survived for 3 hours after injury. Respiratory arrest immediately after exposure to the blast wave and wind was considered to influence the outcome in our pig model. Conclusions Respiratory arrest within several minutes after injury influenced the mortality of pigs. Body armor may have the beneficial effect in protecting against respiratory arrest immediately after an explosion.