Cerebral arterial air embolism: II. Effect of pressure and time on cortical evoked potential recovery.

In a dog model of cerebral arterial gas embolism we studied the relative merits of several different treatments: air breathing at 2.8, 6, 8, and 10 bar (60, 165, 230, and 300 ft), and oxygen breathing at 2.8 bar. The study was confined to the recovery of cortical evoked potentials (CEP) while at pressure. It was confirmed that this was a very severe model; few dogs achieved full recovery and three failed to show any recovery. Injecting 0.4 ml of air into the right internal carotid artery was seen to be as effective in suppressing function in the left hemisphere as in the right. The level of recovery with compression treatment as a percentage of control was directly related to the level to which CEP was suppressed. No other physiological correlates were found with either the degree of CEP suppression or the degree of recovery. Nor was any improvement observed in the rate or maximum amount of recovery at any time out to 20 min as a result of pressures greater than 2.8 bar. Overall, no treatment surpassed oxygen at 2.8 bar.