Studies on lung injuries caused by blast underpressure

This study was designed to determine the effects of underpressure on the lungs of rats and rabbits. An underpressure generator was made to simulate reliably the underpressure parameters at various levels. The peak level and duration ranged from -45.5 kPa to -86.5 kPa and from 21.3 milliseconds to 1,900 milliseconds, respectively. The time to peak negative pressure ranged from 3.5 milliseconds to 7.4 milliseconds. The results showed that underpressure at a certain level could inflict injuries on rats and rabbits. The severity of injury ranged from mild to extremely severe, even to death. These injury patterns were similar to those induced by blast overpressure. The lungs were the organs most vulnerable to underpressure. The pulmonary pathological changes included hemorrhage and edema. The typical hemorrhagic stripes on the lung surfaces resulted from the interfacial impacts of the lungs on the chest wall. The severity of lung injury increased with increased peak pressure and duration levels. This relationship can be expressed with linear regressive equations and the physical parameters of the underpressure can be used to indicate the severity of injury to lungs.