title: Threshold currents of platinum electrodes used for functional electrical stimulation of the phrenic nerves for treatment of central apnea.
abstract: BACKGROUND
  Stability of threshold currents during long-term use of phrenic nerve stimulation has been questioned.
  
  
  RESULTS
  Between January 5, 1988, and March 5, 2008, 49 patients with functional C2-tetraplegia received an Atrostim PNS (Atrotech Ltd., Tampere, Finland) as treatment of their respiratory insufficiency; a follow-up of 35 of such patients was carried out exclusively in our institution for 6.3 (4.44) 0.04-15.75 years (mean [standard deviation (SD)] range). The device employed four-pole sequential nerve stimulation, which provided four threshold currents subsequently evaluated for each phrenic nerve. Stimulation data were prospectively recorded. The differences between threshold currents recorded 1 year after implantation and the last recorded values were 0.33-0.43 (0.44-0.63) 0-2.9 mA. After having excluded the data of eight patients with values >1 mA (= mean + SD), we registered the differences for the remaining patients of 0.15-0.24 (0.14-0.24) 0-0.95 mA, which is just twice the adjustment accuracy of the device. Out of the eight problem cases one had, and two were suspected to have, surgical trauma; all three nerves recovered. In two cases the values steadily increasing over years might have been caused by unspecific foreign body reaction. Two cases with values >1 mA for different durations at different electrodes might be caused by biofilm, and one patient displaying steadily increasing values lived, unwilling to live, only 2 years after the implantation.
  
  
  CONCLUSIONS
  Thus, there was no permanent nerve injury and in 77% of the presented cases threshold currents remained stable.
authors.affiliation: Department of Spinal Cord Injuries, BG Trauma Hospital Hamburg, Hamburg, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Hirschfeld
authors.forename: Hendryk
authors.initials: H
authors.lastname: Vieweg
authors.forename: Arndt P
authors.initials: AP
authors.lastname: Schulz
authors.forename: Roland
authors.initials: R
authors.lastname: Thietje
authors.forename: Gerhard A
authors.initials: GA
authors.lastname: Baer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004056:Differential Threshold; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010791:Phrenic Nerve; D010984:Platinum / Q000737:chemistry; D011782:Quadriplegia / Q000150:complications* / Q000175:diagnosis / Q000534:rehabilitation*; D020182:Sleep Apnea, Central / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control*; D004561:Transcutaneous Electric Nerve Stimulation / Q000295:instrumentation*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D010984:Platinum