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.
Investigation of robotic-assisted tilt-table therapy for early-stage spinal cord injury rehabilitation.
author: Craven CTD.
publication: J Rehabil Res Dev
PubMed ID: 23881763
Damage to the spinal cord compromises motor function and sensation below the level of injury, resulting in paralysis and progressive secondary health complications. Inactivity and reduced energy requirements result in reduced cardiopulmonary fitness and an increased risk of coronary heart disease and cardiovascular complications. These risks may be minimized through regular physical activity. It is proposed that such activity should begin at the earliest possible time point after injury, before extensive neuromuscular degeneration has occurred. Robotic-assisted tilt-table therapy may be used during early-stage spinal cord injury (SCI) to facilitate stepping training, before orthostatic stability has been achieved. This study investigates whether such a stimulus may be used to maintain pulmonary and coronary health by describing the acute responses of patients with early-stage (<1 yr) motor-complete SCI (cSCI) and motor-incomplete SCI (iSCI) to passive, active, and electrically stimulated robotic-assisted stepping. Active participation was found to elicit an increased response from iSCI patients. The addition of electrical stimulation did not consistently elicit further increases. Extensive muscle atrophy was found to have occurred in those patients with cSCI, thereby limiting the potential effectiveness of electrical stimulation. Active participation in robotic-assisted tilt-table therapy may be used to improve cardiopulmonary fitness in iSCI patients if implemented as part of a regular training program.
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.
author: Chelvarajah R.
Upright posture confers numerous medical and social benefits to a spinal cord injured (SCI) patient. Doing so is limited by symptoms of orthostatic hypotension. This is a common secondary impairment among tetraplegic sufferers.
Establish the proportion of SCI patients who are restricted from using standing apparatus, such as standing frames and standing wheelchairs, because of inducing symptomatic orthostatic hypotension or the fear of developing these disabling symptoms.
Survey conducted by Internet-accessible electronic questionnaire. Questionnaire validated for reliability and accuracy.
293 respondents. Mean age 44.6; 76% male. Median time from injury: 7 years. 38% suffered with orthostatic hypotension; majority were complete injuries and all (except one – T12) were T5 or above level. 52% replied that they were using standing wheelchairs or frames. Of these, 59 (20% of total) stated that orthostatic hypotension symptoms were limiting the use of their upright apparatus. Of those who did not use standing wheelchairs or frames, 16 (5.5% of total) reported that this was because of the fear of worsening their orthostatic hypotension.
Orthostatic hypotension restricts standing apparatus use in a large proportion (a total of 25.5% of respondents in this survey) of SCI patients.
date: 2015 Jun;38(2):162-6.
author: Taveggia G.
publication: Int. J Rhabil Res.
The aim of this study is to evaluate the effects of verticalization with or without combined movement of the lower limbs in patients in a vegetative state or a minimally conscious state. In particular, we aimed to study whether, in the group with combined movement, there was better tolerance to verticalization. This was a randomized trial conducted in a neurorehabilitation hospital. Twelve patients with vegetative state and minimally conscious state 3-18 months after acute acquired brain injuries were included. Patients were randomized into A and B treatment groups. Study group A underwent verticalization with a tilt table at 65° and movimentation of the lower limbs with a robotic system for 30 min three times a week for 24 sessions. Control group B underwent the same rehabilitation treatment, with a robotic verticalization system, but an inactive lower-limb movement system. Systolic and diastolic blood pressure and heart rate were determined. Robotic movement of the lower limbs can reduce the occurrence of orthostatic hypotension in hemodynamically unstable patients. Despite the small number of patients involved (only eight patients completed the trial), our results indicate that blood pressures and heart rate can be stabilized better (with) by treatment with passive leg movements in hemodynamically unstable patients.
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.
Use of a device to support standing during a physical activity program to improve function of individuals with disabilities who reside in a nursing home.
To demonstrate the feasibility of an innovative program of physical activity using a standing–support device targeted towards adult residents of a nursing home who are unable to transfer or stand independently.
Thirteen residents, age 82 +/- 11 years, at the Beit Bayer Nursing Home, Jerusalem, Israel, who were unable to transfer or stand independently.
Eight-week observational period followed by 12-week physical activity performed while standing in a Standing–Support Device.
Manual Muscle Testing, joint range of motion, forward and lateral reach, time to stand independently, distance walked with a walker, Functional Independence Measure.
Compared to the observational period, significant post-intervention improvements were noted particularly in lower extremity muscle strength. Improvements in the Functional Independence Measure were noted in sphincter control, locomotion, mobility, motor score, and total score. Over 60% of those previously requiring assistance in standing became able to stand for an average of 1 min unassisted and walk an average of 14 m with a walker.
A pilot program of physical activity using a Standing–Support Device is feasible in selected stance-disabled older adult nursing home residents. Participants showed evidence of muscle strength and functional improvement. Future studies of the device with a concurrent examination of healthcare costs, functional improvement, and staff burden, are recommended.
Cardiovascular and haemodynamic responses to tilting and to standing in tetraplegic patients: a review
This paper has reviewed the acute and long-term responses to changes in vertical posture in normal and tetraplegic subjects. It has discussed physiological mechanisms causing orthostatic hypotension in acute cervical spinal cord injured patients, and subsequent factors contributing to its amelioration over time. The long-term adaptive mechanisms are still controversial, probably involving multiple neurological, endocrine, renal, cardiovascular and haemodynamic factors. These factors include inhibition of vagal tone, plasma catecholamine levels, sensitivity of vascular beds to catecholamines, stretch reflexes in blood vessels, spinal BP reflexes, renin-angiotensin system, aldosterone and plasma volume changes. Individual differences may also interact with these various mechanisms, further complicating the issues. Although the fact that most tetraplegics do improve their orthostatic tolerance over time with repeated tilting is manifest, the precise mechanisms allowing this improvement are not. Research is needed to clarify these adaptive mechanisms, as well as to investigate the physiological effects of long-term therapeutic standing in devices such as standing frames.
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.