Lisa Riedy

Follow-up assessment of standing mobility device users.

The use of standing devices by spinal cord-injured subjects was investigated through a national survey of a sample of individuals who returned their manufacturers warranty card to two companies. We obtained a 32% response rate (99/310). The majority of respondents were male (87%) with a median age between 41 and 50 years. Seventy-seven percent were paraplegic and 21% were quadriplegic. Forty percent had between 1 and 5 years experience with their device, and 84% of those responding were currently using their standing device. Forty-one percent used their standing device one to six times a week; two-thirds stood between 30 minutes and 1 hour for each use. Less than 10% of subjects experienced any side effects, such as nausea or headaches, from standing. Twenty-one percent of subjects reported being able to empty their bladder more completely. There was also a favorable response by some individuals on the effects of the standing devices on bowel regularity, reduction of urinary tract infections, leg spasticity, and number of bed sores. Finally, 79% of subjects highly recommended use of standing devices to other people with spinal cord injury. The positive responses of individuals using standing devices is a strong recommendation for the assistive technology community to make these devices more available to individuals with spinal cord injury.

The effect of electrical stimulation on colonic transit following spinal cord injury in cats.

The effect of direct electrical stimulation on colinic transit and manometric recordings following spinal cord injury were assessed in five adult male cats. Intra-colonic catheters were surgically placed, stimulating electrodes were sutured to the colonic serosa and a laminectomy with spinal cord clamping at a T4 level was done to induce spinal cord injury (SCI). Twenty radiopaque markers were inserted through an intra-colonic catheter located 1 cm distal to the cecum and were monitored with daily fluoroscopy as a measure of colonic transit. Transit measurements were compared before SCI, after SCI and after SCI with electrical stimulation of 40 pps, 1 ms, and 0–50 mA. Colonic transit following SCI was significantly prolonged (P<0.05) when compared to the transit before SCI. Electrical stimulation following SCI improved colonic transit to values not significantly different from those before SCI. Spontaneous colonic phasic motor activity was similar both before and after SCI. Manometric defection patterns were also observed to be similar before SCI and after SCI with electrical stimulation. Based on our scoring criteria, the most frequent response to electrical stimulation was an abdominal contraction. These findings demonstrate that colonic transit is prolonged following SCI and that direct electrical stimulation of the colon following SCI improves colonic transit in an animal model.

Evaluation of direct bladder stimulation with stainless steel woven eye electrodes

Encouraged by recent clinical reports of micturition induced in patients by direct bladder stimulation, we conducted a study of optimum methods of direct bladder stimulation. During surgery six male cats received eight large surface-area woven eye electrodes sutured to the bladder wall serosa, four on the bladder dome and four adjacent to the trigone area. Two additional small surface-area single knot electrodes were sutured in the trigone area. Suprapubic and intraperitoneal tubes were placed for pressure recording and bladder filling. Leg and pelvic floor EMG electrodes were also used for tethered recordings. One to eight weeks after surgery, optimum stimulation methods were evaluated as the animal freely moved about a urodynamic recording cage. Electrodes in the trigone region were more effective than electrodes on the dome and induced bladder contractions and voiding similar to spontaneously induced voiding with bladder filing. Large surface area, woven eye electrodes, composed of multistranded 316LVM stainless steel wire, were more effective than smaller surface area single knot electrodes. High stimulating frequencies (40 Hz) were better than lower frequencies (10 to 20 Hz), and a 1 millisecond pulse duration was optimal. Pulsing with stimulating currents from 10 to 25 mA induced effective bladder contractions with voiding when applied for 3 seconds. However, lower currents using longer stimulation periods were also effective. Bipolar electrodes with both electrodes on the bladder wall were superior to monopolar arrangements with the positive ground electrode along the animals back. We concluded that in the able-bodied cat model, bladder contractile activity for micturition can be induced with direct bladder stimulation and with little discomfort. An effective stimulation protocol consists of capacitor-coupled monophasic pulses with large surface area bipolar electrodes in the trigone region. Stimulating parameters of 40 Hz, 1 msec., 10 to 25 mA applied for 3 seconds were optimal. In addition, based on corrosion resistance observations, the electrodes are quite suitable for long-term studies.

Short-term bladder-wall response to implantation of microstimulators.

This study examined the histological response of the bladder wall serosa to the implantation of wireless microstimulators secured with a single polypropylene suture. Two to three microstimulators were implanted in each of three casts for an eight week implantation period to allow sufficient time for a bladder-wall injury-response to develop. Gross observation revealed encapsulation of the microstimulators with no perforation to the bladder lumen or migration from the bladder wall. Histological evaluation confirmed that all the microstimutators were encapsulated with a thin connective tissue sheath and a thickened subserosal layer. There was no remarkable difference in tissue morphology compared with normal bladder wall sections for five of seven stimulators. Two microstimulators in one cat revealed a moderate to severe inflammatory response confined to a small area around the stimulator. In a second cat, a suture extended through the bladder wall. The microstimulators were observed with a scanning electron microscope after explantation. The electrode surfaces, bonding interface between silicon and glass and insulating films that were exposed to biological fluids were carefully inspected. All these observations indicate that the glass capsule reliably protected the sealed cavity of the microstimulators from moisture. These results indicate the microstimulator should be considered for further studies such as effects of stimulation and long-term implantation.

Direct bladder stimulation with percutaneous electrodes and impedance monitoring of volume in an SCI animal model.

Bladder responses to percutaneous electrodes were investigated with stimulation in three male spinal cats. The animals had been spinalized (T1 level lesion) 10 weeks prior to these studies and had been instrumented with chronic bladder had been spinalized (T1 level lesion) 10 weeks prior to these studies and had been instrumented with chronic bladder wall electrodes and suprapubic bladder catheters for filling and pressure recording. percutaneous stimulation in tethered animals was conducted wit hook electrodes inserted with a needle in the abdomen bilaterally adjacent to the bladder trigone. Stimulation was conducted with 40 Hz pulse trains of 10 to 30 mA for three seconds. Stimulation with both percutaneous and chronic electrodes induced high bladder pressures and voiding. In addition, with chronically implanted electrodes, impedance monitoring of bladder volume was found to be an effective recording technique.

Histological response to implantation of microstimulators on the bladder wall: short term results

Small wireless microstimulators were implanted on the bladder wall serosa in three cats. The microstimulators were secured with a single polypropylene suture. Two to three microstimulators were implanted in each animal. The stimulators were implanted for eight weeks, and gross observation revealed encapsulation of the microstimulators with no perforation into the bladder lumen or migration from the bladder wall. Histological evaluation confirmed that all the microstimulators were encapsulated with a thin connective tissue sheath and a thickened subserosal layer. Only two microstimulators in one cat revealed a moderate to severe inflammatory response confined to a small area around the stimulator. These results indicate that the microstimulator can be further evaluated for implantation and stimulation of the urinary bladder.

Reduced corrosion of pulsed 316LVM stainless steel electrodes by short time constant discharge circuits

The electrochemical charge injection characteristics and corrosion response of single strand 316 LVM stainless steel electrodes were evaluated in vitro using capacitor and coil coupled monophasic charge injection protocols with varying discharge time constants. Positive-first charge injection was used at 44 µC/cm2, stimulating wave forms with short time constants exhibited a less positive potential transients and less corrosion. Multistranded 316LVM electrodes were evaluated with positive and negative-first charge injection with short time constant discharges for more than 300 hours. For both protocols, the potential transients remained fairly constant over the test period and no corrosion was apparent from optical and electron microscopy.