Some effects of vibration on totally immersed cats

¹ Naval Medical Research Institute, Bethesda, Maryland

A survey has been made of the physiological and pathological changes occurring when anesthetized totally immersed cats are exposed to vertical sinusoidal vibration. Twenty-five of 55 cats survived exposure to 15 G peak acceleration for periods averaging 47 min. A decrease in peak acceleration from 15 to 10 G caused a large decrease in mortality. Time of exposure, within the limits of 5–120 min, also affected mortality, but much less strikingly than acceleration. The heart rate and mean respiratory rate are little changed during severe vibration. Respiration becomes irregular, and the tidal volume is greatly depressed. At 15 G peak acceleration, electrocardiographic changes of ischemia and injury occur, especially in those cats which die later. The most significant gross pathological findings are pulmonary collapse and hemorrhage, involving especially the peripheral parts of the lower lobes, and gastrointestinal hemorrhage. The major changes appear to be related to vascular change, either by rupture, leakage, or changes in tone. The resulting ischemia contributes to tissue damage and death. There is both clinical and pathological correlation between the intensity of the forces applied and the response.

Submitted on August 27, 1962