Threshold Currents of Platinum Electrodes used for Functional Electrical Stimulation of the Phrenic Nerves for Treatment of Central Apnea

• Published in: Pacing and clinical electrophysiology 2013-06, Vol.36 (6), p.714-718
• Main Authors: HIRSCHFELD, SVEN, VIEWEG, HENDRYK, SCHULZ, ARNDT P., THIETJE, ROLAND, BAER, GERHARD A.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Child; Child, Preschool; current; diaphragm pacing; Differential Threshold; electrode; Electrodes; Equipment Design; Equipment Failure Analysis; Female; Humans; Infant; Male; Middle Aged; Phrenic Nerve; phrenic nerve stimulation; Platinum - chemistry; Quadriplegia - complications; Quadriplegia - diagnosis; Quadriplegia - rehabilitation; Sleep Apnea, Central - diagnosis; Sleep Apnea, Central - etiology; Sleep Apnea, Central - prevention & control; stimulation; threshold; Transcutaneous Electric Nerve Stimulation - instrumentation; Treatment Outcome; Young Adult
• ISSN: 0147-8389; 1540-8159
• DOI: 10.1111/pace.12073

Background Stability of threshold currents during long‐term use of phrenic nerve stimulation has been questioned. Methods and 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 >1mA 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. Conclusion Thus, there was no permanent nerve injury and in 77% of the presented cases threshold currents remained stable.