title: Safety of multi-channel stimulation implants: a single blocking capacitor per channel is not sufficient after single-fault failure.
abstract: One reason given for placing capacitors in series with stimulation electrodes is that they prevent direct current flow and therefore tissue damage under fault conditions. We show that this is not true for multiplexed multi-channel stimulators with one capacitor per channel. A test bench of two stimulation channels, two stimulation tripoles and a saline bath was used to measure the direct current flowing through the electrodes under two different single fault conditions. The electrodes were passively discharged between stimulation pulses. For the particular condition used (16 mA, 1 ms stimulation pulse at 20 Hz with electrodes placed 5 cm apart), the current ranged from 38 to 326 μA depending on the type of fault. The variation of the fault current with time, stimulation amplitude, stimulation frequency and distance between the electrodes is given. Possible additional methods to improve safety are discussed.
authors.affiliation: Biomedical Stimulation and Monitoring Research Group, Université Libre de Bruxelles, Avenue FD Roosevelt 50 CP165/51, 1050 Brussels, Belgium. anoncler@ulb.ac.be
authors.forename: Antoine
authors.initials: A
authors.lastname: Nonclercq
authors.forename: Laurent
authors.initials: L
authors.lastname: Lonys
authors.forename: Anne
authors.initials: A
authors.lastname: Vanhoestenberghe
authors.forename: Andreas
authors.initials: A
authors.lastname: Demosthenous
authors.forename: Nick
authors.initials: N
authors.lastname: Donaldson
mesh_terms: D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004582:Electronics, Medical / Q000295:instrumentation*; D004867:Equipment Design; D004868:Equipment Failure; D004869:Equipment Safety; D006801:Humans; D019736:Prostheses and Implants