Kerry Bradley

Factors Affecting Impedance of Percutaneous Leads in Spinal Cord Stimulation

Objectives.u2002 Although the load impedance of a pulse generator has a significant effect on battery life, the electrical impedance of contact arrays in spinal cord stimulation (SCS) has not been extensively studied. We sought to characterize the typical impedance values measured from common quadripolar percutaneous SCS contact arrays.

Real-Time Paresthesia Steering Using ContinuousElectric Field Adjustment. Part I: IntraoperativePerformance

We present data collected from a multicenter study using a new neurostimulation system. This new system uses a current‐shifting programming technique for spinal cord stimulation. The system maintains a continuous, suprathreshold stimulation field while adjusting the distribution of anodic and cathodic current among contacts along a multi‐contact array. The changing distribution of current shifts the electric field along the spinal cord, resulting in real‐time, dynamic paresthesia steering. This process of adjusting the stimulation field has been termed continuous electric field adjustment (CEFA). This technique has been used to assess paresthesia coverage for patients undergoing implantation of stimulation contact arrays for chronic pain. This multicenter study evaluated the performance of the CEFA technique. The results of the study showed that paresthesia coverage could be shifted in real‐time to different regions on the patients body in a comfortable fashion, with the patient always feeling paresthesia during the adjustment process. The results of the study also show that the process was time‐efficient: intraoperatively, the median time to assess 71 combinations on a single 8‐contact lead across 18 patients was 4.1 (3.6–5.0) minutes.

Theoretical Investigation Into Longitudinal Cathodal Field Steering in Spinal Cord Stimulation

Objective.u2002 When using spinal cord stimulation (SCS) for chronic pain management, precise longitudinal positioning of the cathode is crucial to generate an electrical field capable of targeting the neural elements involved in pain relief. Presently used methods have a poor spatial resolution and lack postoperative flexibility needed for fine tuning and reprogramming the stimulation field after lead displacement or changes in pain pattern. We describe in this article a new method, “electrical field steering,” to control paresthesia in SCS. The method takes advantage of newer stimulator design and a programming technique allowing for “continuous” adjustment of contact combination while controlling stimulation current for each contact separately.

A Preliminary Feasibility Study of Different Implantable Pulse Generators Technologies for Diaphragm Pacing System

Diaphragm pacing stimulation (DPS) for ventilator‐dependent patients provides several advantages over conventional techniques such as phrenic nerve pacing or mechanical ventilator support. To date, the only existing system for DPS uses lead electrodes, percutaneously attached to an external pulse generator (PG). However, for a widespread use of this technique it would be more appropriate to eliminate the need for percutaneous wire and use a totally implantable system. The aim of this study was to determine if it were feasible to replace the external PG by an implantable system. We present here the results of a preliminary study of two different PG, currently used in other electrical stimulation (ES) clinical applications, which could be used as implantable DPS systems. One radio‐frequency‐powered PG, one rechargeable battery‐powered PG, and the current external PG were tested. Each was attached to the externalized part of the wires, connected to the diaphragm and tidal volume (TV) was measured in one ventilator‐dependent patient who has been using the current percutaneous stimulator for 3 years. Results indicated that both implantable PGs could achieve equivalent ventilatory requirements to the current external stimulator. No significant differences were observed between the three PG systems when stimulating the electrodes as used in the patients own chronically attached PG system. We found that TV increased with increases in charge and frequency as expected when stimulating the patients electrodes individually and in combination with each PG system. These results are a significant step toward developing a totally implantable DPS system for the ventilator‐dependant patients. Further clinical tests to demonstrate the safety and efficacy of a fully implanted DPS system are warranted.