Electroventilation in the baboon.

The optimum sites for chest-surface electrodes and the relationship between the inspired volume of air and stimulus intensity were determined in six pentobarbital-anesthetized baboons. The optimum stimulation sites were identified using hand-held, trans-chest stimulating electrodes. Thereafter, conducting adhesive electrodes 4 cm in diameter were placed over each of the optimal sites. The relationship between inspired volume and stimulus intensity was determined with the forelimbs restrained and unrestrained using an 800-msec burst of 60/sec stimuli with a pulse duration of 20 microseconds. Two optimum stimulation sites were identified, one in the anterior axillary region, and another just lateral to the xiphoid process. The maximum volume of inspired air was obtained when the stimulating electrodes were placed at the anterior axillary sites. With the forelimbs restrained or unrestrained, an increased stimulus intensity resulted in an inspired volume well in excess of the spontaneous tidal volume of the animal. These studies indicate that, with chest-surface electrodes at the optimal locations, electroventilation can produce inspired volumes greater than spontaneous tidal volume in anesthetized baboons. With electrodes in the xiphoid region a smaller maximum inspired volume was obtained because of the stimulation of expiratory (abdominal) muscles.