Follow up Study of Diaphragm Pacing for Patients With High Tetraplegia

Overview

This is an observational longitudinal study designed to identify and describe long term outcomes for patients with high tetraplegia who use a Diaphragmatic Pacing System (DPS). As this is not a randomized or experimental study, no specific hypotheses are proposed. The data collected will enable us to answer the following research questions: 1. What are the patterns of long-term DPS use (hours per day using DPS, changes in DPS stimulus parameters, abandonment of DPS and related reasons). 2. What mechanical problems have DPS users encountered (system failure, repairs needed)? 3. What are the frequency of and reasons for rehospitalization following DPS implant? 4. What levels of care are needed at home to manage the DPS? 5. How do DPS users feel about the system (satisfaction, comfort, vocalization, taste, swallowing)?

Ventilatory dependent high tetraplegia is a relatively rare but devastating condition. Review of National Spinal Cord Injury Database statistics show that only 3.6% of patients with tetraplegia are ventilator dependent at one year post injury.1 A subset of individuals who are ventilatory dependent in the long term and have upper motor neuron paralysis of the diaphragm are candidates for electrophrenic respiration (EPR) which can create inspiratory function through electrical stimulation of the phrenic nerves, resulting in diaphragmatic contraction. The use of this technology in ventilatory dependent tetraplegia was first described almost 40 years ago with a pacing system using cuff electrodes surgically placed around the phrenic nerve in the neck.2 The concept of EPR via minimally invasive laparoscopically placed diaphragmatic electrodes was first reported in 2002.3 This new Diaphragmatic Pacing System (DPS) had the distinct advantage of requiring less invasive surgery for electrode implantation compared to the phrenic cuff electrode system which required surgical exploration of the neck. In some settings, the DPS system has been implanted as an outpatient surgery. The DPS had a potential disadvantage however in that, unlike the traditional EPR system, the stimulating electrode leads are externalized posing an infection risk and the electrodes are attached to a moving muscle creating a risk for dislodgement. Once the system achieved FDA Humanitarian Use Device (HUD) exemption status in 2008, there was adoption of the Diaphragm Pacing System (DPS) among a number of SCI centers as a treatment option for patients with ventilatory dependent high tetraplegia. Reporting of long-term outcomes of DPS in the SCI population is limited to a 2009 report authored by the system inventor on 50 patients with average follow-up of 2.0 ± 1.5 years (median 1.6 years, range 0.5-8.0 years).4 The six SCIMS centers participating in this module research propose to collect long-term follow-up data on DPS patients implanted and/or followed at their centers since 2007. This project will enable the reporting of independent long-term utilization, effectiveness, satisfaction, durability and safety outcomes of this innovative technology.