Muscular Activity and Bubble Formation in Animals Decompressed to Simulated Altitudes

1. Muscular activity during decompression causes bubble formation in the blood of intact bullfrogs. The amount of gas liberated depends on the degrees of muscular activity and supersaturation (as influenced by altitude). In decompressed dissected bullfrogs, bubbles appear in veins leading from active but not from inactive muscles. 2. Muscular activity during decompression similarly causes bubble formation in rats. Bubbles appear in veins coming from muscles, and often in the lymphatic system. Quiescent rats do not form bubbles. 3. Violent muscular activity before decompression favors bubble formation in bullfrogs during ensuing decompression, but it is less effective than exercise during decompression. The effect persists in large frogs for about an hour. 4. Pre-oxygenation for 2 to 4 hours before decompression reduces the incidence of bubble formation in decompressed bullfrogs. It thus has the same effect on bubble formation in bullfrogs as it does on the "bends" in man. The effect is presumably due to removal of nitrogen. 5. Possible mechanisms by which muscular activity causes bubble formation are discussed. The effects of mechanical agitation and of metabolic CO(2) are considered to be the dominant factors.