Cardiovascular response of individuals with spinal cord injury to dynamic functional electrical stimulation under orthostatic stress
date: 2013 Jan;21(1):37-46.
author: Yoshida T.
publication: IEEE Trans Neural Syst Rehabil Eng.
PubMed ID: 22899587
In this pilot study, we examined how effectively functional electrical stimulation (FES) and passive stepping mitigated orthostatic hypotension in participants with chronic spinal cord injury (SCI). While being tilted head-up to 70 (°) from the supine position, the participants underwent four 10-min conditions in a random sequence: 1) no intervention, 2) passive stepping, 3) isometric FES of leg muscles, and 4) FES of leg muscles combined with passive stepping. We found that FES and passive stepping independently mitigated a decrease in stroke volume and helped to maintain the mean blood pressure. The effects of FES on stroke volume and mean blood pressure were greater than those of passive stepping. When combined, FES and passive stepping did not interfere with each other, but they also did not synergistically increase stroke volume or mean blood pressure. Thus, the present study suggests that FES delivered to lower limbs can be used in individuals with SCI to help them withstand orthostatic stress. Additional studies are needed to confirm whether this use of FES is applicable to a larger population of individuals with SCI.
Electrically induced and voluntary activation of physiologic muscle pump: a comparison between spinal cord-injured and able-bodied individuals.
date: 2002 Dec;16(8):878-85.
author: Faghri PD.
publication: Clin Rehabil
To evaluate the central haemodynamic responses during position changes from supine to sitting and during 30 min of standing between able-bodied and spinal cord-injured subjects. Also to assess the effects of the physiologic muscle pump in both groups during 30 min of standing.
A repeated measure design. Both groups were tested on two different days under two conditions of 30 min of stationary standing and 30 min of dynamic standing (voluntary activation of the lower leg muscles in able-bodied and FES-induced activation of these muscles in spinal cord injured). The order of testing was random.
Fifteen healthy able-bodied and 14 healthy spinal cord-injured subjects.
MAIN OUTCOME MEASURED:
Stroke volume, cardiac output, heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure and total peripheral resistance during supine-pre sitting, sitting-pre standing and during 30 min of standing.
Significant reductions (p < 0.05) in systolic blood pressure, diastolic blood pressure and mean arterial pressure were found when spinal cord-injured subjects moved from sitting to standing during stationary standing; these values were maintained during dynamic standing. These values were maintained during both standing sessions in able-bodied subjects. During 30 min of stationary standing, there were significant reductions in stroke volume, cardiac output in both able-bodied and spinal cord-injured while their total peripheral resistance increased (p < 0.05). During 30 min of dynamic standing, both groups maintained their haemodynamics at pre-standing values with the exception of significant reduction in stroke volume at 30 min of standing.
FES-induced activation of the physiologic muscle pump during change in position from sitting to standing prevented orthostatic hypotension in spinal cord-injured subjects. During standing it had equal or even greater effect on improving blood circulation when compared with voluntary activation in able-bodied subjects. The use of FES during standing and tilting in spinal cord-injured individuals may prevent orthostatic hypotension and circulatory hypokinesis and improve tolerance to tilting and standing.
The effects of lower-extremity functional electric stimulation on the orthostatic responses of people with tetraplegia.
date: 2005 Jul;86(7):1427-33.
author: Chao CY.
publication: Arch Phys Med Rehabil
To determine whether application of functional electric stimulation (FES) to lower-limb muscles during postural tilting improves orthostatic tolerance in people with tetraplegia.
A crossover design.
A rehabilitation hospital.
Sixteen acute and chronic subjects with tetraplegia (15 men, 1 woman) with complete motor function loss at the C3-7 levels were recruited. Time since injury ranged from 2 to 324 months (mean, 118.9+/-104.2 mo).
Subjects were tested on a progressive head-up tilting maneuver with and without the application of FES at 0 degrees , 15 degrees , 30 degrees , 45 degrees , 60 degrees , 75 degrees , and 90 degrees continuously for up to 1 hour. FES was administered to 4 muscle groups including the quadriceps, hamstrings, tibialis anterior, and gastrocnemius muscles bilaterally at an intensity that provided a strong, visible, and palpable contraction. This was to produce a muscle pumping mechanism during the tilting maneuver.
MAIN OUTCOME MEASURES:
Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, perceived presyncope score, and the overall duration of orthostatic tolerance, that is, the time that subjects could tolerate the tilting maneuver without developing severe hypotension or other intolerance symptoms.
When the tilt angle was increased, the subjects’ SBP and DBP tended to decrease, whereas the heart rate tended to increase in both testing conditions. Adding FES to tilting significantly attenuated the drop in SBP by 3.7+/-1.1 mmHg (P = .005), the drop in DBP by 2.3+/-0.9 mmHg (P = .018), and the increase in heart rate by 1.0+/-0.5 beats/min (P = .039) for every 15 degrees increment in the angle of the tilt. FES increased the overall mean standing time by 14.3+/-3.9 min (P = .003).
An FES-induced leg muscle contraction is an effective adjunct treatment to delay orthostatic hypotension caused by tilting; it allows people with tetraplegia to stand up more frequently and for longer durations.
Early poststroke rehabilitation using a robotic tilt-table stepper and functional electrical stimulation
author: Kuznetsov AN,
publication: Stroke Res Treat.
Background. Stroke frequently leaves survivors with hemiparesis. To prevent persistent deficits, rehabilitation may be more effective if started early. Early training is often limited because of orthostatic reactions. Tilt-table stepping robots and functional electrical stimulation (FES) may prevent these reactions. Objective. This controlled convenience sample study compares safety and feasibility of robotic tilt-table training plus FES (ROBO-FES) and robotic tilt-table training (ROBO) against tilt-table training alone (control). A preliminary assessment of efficacy is performed. Methods. Hemiparetic ischemic stroke survivors (age 58.3 ± 1.2 years, 4.6 ± 1.2 days after stroke) were assigned to 30 days of ROBO-FES (n = 38), ROBO (n = 35), or control (n = 31) in addition to conventional physical therapy. Impedance cardiography and transcranial doppler sonography were performed before, during, and after training. Hemiparesis was assessed using the British Medical Research Council (MRC) strength scale. Results. No serious adverse events occurred; 8 patients in the tilt-table group prematurely quit the study because of orthostatic reactions. Blood pressure and CBFV dipped <10% during robot training. In 52% of controls mean arterial pressure decreased by ≥20%. ROBO-FES increased leg strength by 1.97 ± 0.88 points, ROBO by 1.50 ± 0.85 more than control (1.03 ± 0.61, P < 0.05). CBFV increased in both robotic groups more than in controls (P < 0.05). Conclusions. Robotic tilt-table exercise with or without FES is safe and may be more effective in improving leg strength and cerebral blood flow than tilt table alone.
date: 2007 Jun;86(6):499-506
author: Edwards LC, Layne CS.
publication: Am J Phys Med Rehabil
To determine whether individuals who have a spinal cord injury have neuromuscular and physiologic responses to a personalized exercise program during dynamic weight bearing (DWB).
Four subjects with spinal cord injuries (T6, T5-6, C2-5, and C5) completed a 12-wk exercise program that included DWB. Surface electromyography (EMG) was recorded from the right gastrocnemius, biceps femoris, rectus femoris, rectus abdominus, and external oblique. Heart rate (HR) and blood pressure (BP) were recorded throughout training. Descriptive statistics were used to analyze the data.
The results of this study indicate that the subjects actively responded to exercise during DWB, as measured by EMG, HR, and BP.
The results suggest that exercise during DWB can induce physiologic and neuromuscular responses in individuals who have a spinal cord injury, and that exercise during DWB may serve as a preparatory program for more advanced rehabilitation.
Physiologic responses to electrically assisted and frame-supported standing in persons with paraplegia
Systems of functional electrical stimulation (FES) have been demonstrated to enable some persons with paraplegia to stand and ambulate limited distances. However, the energy costs and acute physiologic responses associated with FES standing activities have not been well investigated.
To compare the physiologic responses of persons with paraplegia to active FES-assisted standing (AS) and frame-supported passive standing (PS).
Fifteen persons with paraplegia (T6-T11) previously habituated to FES ambulation, completed physiologic testing of PS and AS. The AS assessments were performed using a commercial FES system (Parastep-1; Altimed, Fresno, Calif); the PS tests used a commercial standing frame (Easy Stand 5000; Altimed, Fresno, Calif). Participants also performed a peak arm-cranking exercise (ACE) test using a progressive graded protocol in 3-minute stages and 10-watt power output increments to exhaustion. During all assessments, metabolic activity and heart rate (HR) were measured via open-circuit spirometry and 12-lead electrocardiography, respectively. Absolute physiologic responses to PS and AS were averaged over 1-minute periods at 5-minute intervals (5, 10, 15, 20, 25, and 30 minutes) and adjusted relative to peak values displayed during ACE to determine percentage of peak (%pk) values. Absolute and relative responses were compared between test conditions (AS and PS) and across time using two-way analysis of variance.
The AS produced significantly greater values of VO2 (43%pk) than did PS (20%pk). The mean HR responses to PS (100-102 beats per minute [bpm] throughout) were significantly lower than during AS, which ranged from 108 bpm at 5 minutes to 132 bpm at test termination.
Standing with FES requires significantly more energy than does AS and may provide a cardiorespiratory stress sufficient to meet minimal requirements for exercise conditioning.
author: Cybulski GR, Penn RD, Jaeger RJ.
publication: Neurosurgery. 1984 Jul;15(1):132-46.
Functional neuromuscular stimulation (FNS) provides a mechanism for the activation of muscles paralyzed by injury to the spinal cord. Although this technique was first used to treat patients with spinal cord injury over 20 years ago, only recent advances in electronics and biomechanics have made it a promising aid for the rehabilitation of these patients. Thus far, restoration of palmar prehension and lateral prehension in quadriplegics and of standing and biped gait in paraplegics has been achieved under carefully controlled laboratory conditions. This article reviews the current status of FNS and its potential as a practical tool to aid spinal cord-injured patients. Neurosurgeons who care for these patients might be expected to be involved in the future use of FNS if implantable systems are developed and tested.
author: Jaeger RJ, Yarkony GM, Roth EJ, Lovell L.
publication: Paraplegia. 1990 Oct;28(8):505-11
Many laboratory demonstrations have been reported on standing or walking with the aid of electrical stimulation. These demonstrations have typically been in small numbers of selected spinal cord injured individuals. The extent to which this technology might ultimately be applicable to the spinal cord injured population at large is not presently known. This study reports estimates of the size of the potential user population of a specific surface electrical stimulation device and protocol. The medical records were reviewed of 192 patients with traumatic thoracic, lumbar, or sacral spinal cord injury resulting in paraplegia. Based on the inclusionary criteria, between 20 and 48 patients (10.4% and 25%) of this sample population could be considered eligible for this surface stimulation protocol. As approximately 45% of the USA population of spinal cord injured individuals have paraplegia, the results suggest that between 4.7% and 11.25% of all spinal cord injured persons in the USA might be potential users of this particular electrical stimulation technology.
author: Yarkony GM, Jaeger RJ, Roth E, Kralj AR, Quintern J.
publication: Arch Phys Med Rehabil. 1990 Mar;71(3):201-6.
A study was undertaken to determine if functional neuromuscular stimulation could be used to obtain standing in patients with traumatic spinal cord injury. Twenty-five subjects were selected during the study, and standing was accomplished in 21 using bilateral quadriceps stimulation with the hips in hyperextension. Four subjects elected not to continue participation to the point of standing. Stimulation parameters were 0 to 120V pulse amplitude, frequency 13Hz or 20Hz, and pulse width of 0.4msec. Confirmation of standing with support of 95% of the body weight by the legs was verified by quantitative measurements with a dual-scale force platform or a biomechanics force platform. Subjects initially selected had injury levels between C7 and T11 and ranged in age from 22 to 47 years, with duration of injury from one to 13 years. The subjects had complete lesions, with no active motor function below the last normal level, and absent sensation or partial sparing of sensation with vague perception of pinprick, but no position sense. Six subjects stood at home and 15 stood only in the laboratory. This five-year experience indicates that paraplegic individuals may obtain standing with functional neuromuscular stimulation.