Lower Thoracic Spinal Cord Stimulation to Restore Cough in Patients With Spinal Cord Injury: Results of a National Institutes of Health–Sponsored Clinical Trial. Part I: Methodology and Effectiveness of Expiratory Muscle Activation
Presented in part to the Congress of Neurological Surgeons, October 7–12, 2006, Chicago, IL; the American Spinal Injury Association, May 30–June 2, 2007, Tampa, FL; the International Spinal Cord Society, June 27–July 1, 2007, Reykjavik, Iceland; the American Paraplegia Society, August 27–29, 2007, Orlando, FL; the American Academy of Physical Medicine and Rehabilitation, September 27–30, 2007, Boston, MA; the American Thoracic Society, May 16–21, 2008, Toronto, ON, Canada; and the American Spinal Injury Association, August 8–11, 2008, Orlando, FL.
Abstract
DiMarco AF, Kowalski KE, Geertman RT, Hromyak DR. Lower thoracic spinal cord stimulation to restore cough in patients with spinal cord injury: results of a National Institutes of Health–sponsored clinical trial. Part I: methodology and effectiveness of expiratory muscle activation.
Objective
Evaluation of the capacity of lower thoracic spinal cord stimulation (SCS) to activate the expiratory muscles and generate large airway pressures and high peak airflows characteristic of cough, in subjects with tetraplegia.
Design
Clinical trial.
Setting
Inpatient hospital setting for electrode insertion; outpatient setting for measurement of respiratory pressures; home setting for application of SCS.
Participants
Subjects (N=9; 8 men, 1 woman) with cervical spinal cord injury and weak cough.
Interventions
A fully implantable electrical stimulation system was surgically placed in each subject. Partial hemilaminectomies were made to place single-disk electrodes in the epidural space at the T9, T11, and L1 spinal levels. A radiofrequency receiver was placed in a subcutaneous pocket over the anterior portion of the chest wall. Electrode wires were tunneled subcutaneously and connected to the receiver. Stimulation was applied by activating a small portable external stimulus controller box powered by a rechargeable battery to each electrode lead alone and in combination.
Main Outcome Measures
Peak airflow and airway pressure generation achieved with SCS.
Results
Supramaximal SCS resulted in high peak airflow rates and large airway pressures during stimulation at each electrode lead. Maximum peak airflow rates and airway pressures were achieved with combined stimulation of any 2 leads. At total lung capacity, mean maximum peak airflow rates and airway pressure generation were 8.6±1.8 (mean ± SE) L/s and 137±30 cmH2O (mean ± SE), respectively.
Conclusions
Lower thoracic SCS results in near maximum activation of the expiratory muscles and the generation of high peak airflow rates and positive airway pressures in the range of those observed with maximum cough efforts in healthy persons.
aDepartment of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH
bDepartment of Neurological Surgery, Case Western Reserve University, Cleveland, OH
cDivision of Neurological Surgery, MetroHealth Medical Center, Cleveland, OH
Correspondence to Anthony F. DiMarco, MD, MetroHealth Medical Center, Rammelkamp Center for Education and Research, 2500 MetroHealth Dr, Cleveland, OH 44109
Supported by the National Institute of Neurological Disorders and Stroke (grant no. R01 NS049516) and the National Center for Research Resources (grant no. M01 RR 00080 and UL1 RR024989). Clinical Trial Registration Number:NCT00116337.
We certify that we have affiliations with or financial involvement (eg, employment, consultancies, honoraria, stock ownership or options, expert testimony, grants and patents received or pending, royalties) with an organization or entity with a financial interest in, or financial conflict with, the subject matter or materials discussed in the article. Dr. DiMarco is a founder of and has a significant financial interest in Synapse BioMedical, Inc, a manufacturer of diaphragm pacing systems.
ABSTRACT