The Effects of Shock Tube Generated, Step-rising Overpressures on Guinea Pigs Located in Shallow Chambers Oriented Side-on and End-on to the Incident Shock

A total of 308 guinea pigs were exposed to air blast in 4 close-fitting, shallow, rectangular chambers mounted on the top, bottom and sides of an air-driven shock tube. With a reflecting plate at the downstream edge of the chambers, the animals were exposed to long-duration shock overpressures that initially rose in a single step. The LD50-24-hr reflected pressure calculated from grouping all positions was 36.2! 0.8 psi. By moving the reflecting plate to various distances downstream of the chambers, shock overpressures that initially rose in two steps were applied. The results were that the animals' tolerances to overpressure rose as the time between pressure steps was increased. Comparison of the LD50's obtained with animals in each chamber revealed that there was not a significant statistical difference in their tolerances, whether they were loaded initially with the single-step pulse from their right, left, dorsal or ventral surfaces. (Author).