Acute effects of air blast on pulmonary function in dogs and sheep.

Abstract : Pulmonary function tests were conducted before and after exposure of animals to air blasts produced in shock tubes or by high explosives. Pressure- time measurements were made with piezoelectric pressure transducers during each air-blast exposure. Blood samples were obtained without anesthesia from an indwelling arterial catheter. The blood PO2, PCO2, and pH and the end-tidal and mixed expired CO2, O2, and N2 gas concentrations were measured for subjects breathing air and oxygen. There were increases in the alveolar-arterial O2 differences and venous admixture which generally correlated with the extent of blast-induced lung damage. The threshold for lung injury resulting in increased venous admixture in sheep was about 20 psi for reflected overpressures of 'long' duration. Pressures above 43 psi usually caused severe lung damage in which the venous-arterial shunt exceeded 30 percent of the cardiac output, a condition in which the arterial oxygen tension was below the level required for full saturation of the hemoglobin even with animals breathing pure oxygen.