Electroventilation with monopolar and bipolar intratracheal electrodes.

UNLABELLED: Electroventilation is the technique of producing inspiration with stimuli applied to inspiratory muscles by using strategically placed electrodes on or within the body. We conducted studies using the dog to determine the efficacy of monopolar and bipolar intratracheal electrodes for electroventilation. Bipolar electrodes were able to produce an inspired volume greater than a spontaneous tidal volume in all seven dogs, but monopolar electrodes were able to in only three of seven dogs. The intratracheal electrode has the advantage over body-surface electrodes that less current is required to produce a single tidal volume, and it has the advantage over intraesophageal electrodes that anatomical placement of the electrode is simplified. These experiments demonstrated that a bipolar electrode can be used for electroventilation. IMPLICATIONS: This study demonstrates that electroventilation is possible with intratracheal electrodes, decreasing the current needed to electroventilate by using body-surface electrodes. Two different methods of intratracheal electroventilation can be used: monopolar, in which the return electrode is on the body surface; and bipolar, in which the return electrode is in the trachea.

Comparison of the threshold for peripheral nerve stimulation during gradient switching in whole body MR systems.

PURPOSE: To compare thresholds for peripheral nerve stimulation from gradient switching in whole body magnetic resonance (MR) equipment of different design. MATERIALS AND METHODS: Threshold data obtained in three experiments were reformatted into a single joint data set describing thresholds for anterio-posterior (AP) gradient orientation and Echo Planar Imaging (EPI) waveforms with bipolar ramp times between 0.07 and 1.2 ms. Reformatting included the use of: a) the rate of change of the maximum field in the patient space as a measure of gradient output, b) lowest observable thresholds, c) lognormal distribution of thresholds, and d) equal standard deviation (SD) of all samples. RESULTS: The joint data fit a hyperbolic threshold function. The residues were not significantly different between experiments. CONCLUSION: Then expressed in appropriate format, the thresholds for peripheral nerve stimulation in volunteers for whole body MR equipment can be described with a hyperbolic threshold curve with rheobase 18.8 +/- 0.6 Tesla/second and chronaxie 0.36 +/- 0.02 milliseconds.