Conduction block in mammalian nerve produced by O₂ at high pressure

¹ Neurophysiology Branch, U.S. Naval Medical Research Institute, Bethesda, Maryland

Oxygen at high pressure causes a block of conduction in the peripheral nerves of mammals. The interval between initiation of exposure to high oxygen pressure and the onset of block is inversely related to the partial pressure of the oxygen. If the block is not maintained for more than a few minutes, recovery of the ability to conduct returns to the nerve upon decompression. The sensitivity of mammalian nerve to the toxic effects of oxygen at high pressure is decreased when the partial pressure of carbon dioxide in the atmosphere is high, whereas if the partial pressure of carbon dioxide in the atmosphere is lower than normal, the sensitivity of the nerve to the effects of high pressure oxygen increases. This is contrary to the effect carbon dioxide has on oxygen toxicity in frog peripheral nerves. Increased metabolic activity, as occurs at high stimulation frequencies, shortens the time required for block; decreased metabolic activity, as occurs when nerves are cooled, delays the onset of block.