THE EFFECTS OF AMBIENT PRESSURE ON THE TOLERANCE OF MICE TO AIR BLAST

Mice were exposed to overpressures of 'long' duration in the expansion chamber of an air-driven shock tube inside which the initial, pre- blast pressures were varied over sixfold. When the animals were held at the initial pressure for one hour following the blast before being returned to the ambient pressure of the laboratory, tolerance values, expressed as LD50-l-hour gauge pressures, increased fourfold; they were 20.3, 31.0, 44.5, 55.4, and 91.8 psi for initial pressures of 7, l2, 18, 24, and 42 psia, respectively. When animals were returned to ambient level soon after blast exposure, the LD50 pressures were lower than the above values for initial pressures greater than ambient and higher for initial pressures lower than ambient. The feasibility of scaling biological blast effects as a function of altitude is discussed and one approach suggested by available empirical data is regarded as a promising, but tentative procedure. Presented before the Symposium on the Biological Effects of Blast and Shock. Headquarters Field Command Defense Atomic Support Agency, Sandia Base, Albuquerque, New Mexico, April 20, l963.