Development of a new experimental model of intramuscular electrical stimulation of the diaphragm in rabbits

To develop an animal model of diaphragmatic electrical stimulation able to generate an appropriate ventilatory support through the direct implantation of electrodes in the diaphragm (electroventilation).

Six New Zealand female rabbits (2-3 kg) were placed on mechanical ventilation. Then, a laparotomy was performed in order to identify the motor points in each hemidiaphragm, followed by the implantation of the electrodes for diaphragmatic stimulation. We tested two types of electrodes according to the conduction of electrical stimulation: unipolar and bipolar. The electrodes were placed on different occasions in the same animals and tested with current intensities of 20, 26 and 32 mA. Each current intensity was repeated three times for 10 respiratory cycles with 1 minute interval between each cycle, and 5 minutes for new current intensity. We recorded the relationship between current intensity and inspiratory volume.

The electrodes adequately stimulate the diaphragm and obtain inspired volumes using different intensity currents. The bipolar electrode generated inspiratory volumes as high as 4.5 times of baseline while the unipolar electrode reached up to 3.5 times of baseline.

This model has proved to be effective for studying the performance of the diaphragm under different electrical stimulations using different set of electrodes.