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.
Effect of weight-bearing activities on bone mineral density in spinal cord injured patients during the period of the first two years.
author: Alekna V, Tamulaitiene M, Sinevicius T, Juocevicius A.
publication: Spinal Cord. 2008 Nov;46(11):727-32. Epub 2008 Apr 29.
STUDY DESIGN: Prospective study on patients with spinal cord injuries. OBJECTIVES: To evaluate the loss of bone mineral density (BMD) in various body regions of patients with spinal cord injury (SCI) and its dependence on weight bearing activities during 2 years post injury. METHODS: BMD of the whole body was measured in patients with SCI. Baseline measurement was performed in 6-16 weeks after SCI, the second and the third-respectively 12 and 24 months after injury. Fifty-four subjects were selected and divided into two groups: standing and non-standing. From these groups 27 pairs were made according to gender, age and height. RESULTS: There was found to be a well-marked decrease in BMD values for lower extremities, but there was no significant difference between paraplegic and tetraplegic patients 1 and 2 year after injury. Leg BMD reduced by 19.62% (95% CI, 17-22%) in the standing group and by 24% (95% CI, 21-27%) in non-standing group during the first year. Two years after SCI patients in standing group had significantly higher leg BMD-1.018 g/cm(2) (95% CI, 0.971-1.055 g/cm(2)) than in the non-standing group-0.91 g/cm(2) (95% CI, 0.872-0.958 g/cm(2)) (P<or=0.0001). CONCLUSION: SCI patients who performed daily standing >or=1 h and not less than 5 days per week, had significantly higher BMD in the lower extremities after 2 years in comparison to those patients who did not perform standing.
Randomised trial of the effects of four weeks of daily stretch on extensibility of hamstring muscles in people with spinal cord injuries.
author: Harvey LA, Byak AJ, Ostrovskaya M, Glinsky J, Katte L, Herbert RD.
publication: Aust J Physiother. 2003;49(3):176-81.
The aim of this assessor-blind randomised controlled trial was to determine the effect of four weeks of 30 minute stretches each weekday on extensibility of the hamstring muscles in people with recent spinal cord injuries. A consecutive sample of 16 spinal cord-injured patients with no or minimal voluntary motor power in the lower limbs and insufficient hamstring muscle extensibility to enable optimal long sitting were recruited. Subjects’ legs were randomly allocated to experimental and control conditions. The hamstring muscles of the experimental leg of each subject were stretched with a 30 Nm torque at the hip for 30 minutes each weekday for four weeks. The hamstring muscles of the contralateral leg were not stretched during this period. Extensibility of the hamstring muscles (hip flexion range of motion with knee extended, measured with a 48 Nm torque at the hip) of both legs was measured by a blinded assessor at the commencement of the study and one day after the completion of the four-week stretch period. Changes in hamstring muscle extensibility from initial to final measurements were calculated. The effect of stretching was expressed as the mean difference in these changes between stretched and non-stretched legs. The mean effect of stretching was 1 degree (95% CI -2 to 5 degrees). Four weeks of 30 minute stretches each weekday does not affect the extensibility of the hamstring muscle in people with spinal cord injuries.
author: Ferguson-Pell MW, Wilkie IC, Reswick JB, Barbenel JC.
publication: Paraplegia. 1980 Feb;18(1):42-51.
The concept of a wheelchair cushion fitting clinic for the prevention of pressure sores is reviewed in the light of recent estimates of the cost of pressure sores in the U.K. A method for measuring the pressure beneath the ischial tuberosities is discussed and techniques for measuring a patient’s habitual exercise frequency and seated posture are described. Results from the records of 600 spinal injury patients including Rancho Los Amigos Hospital are reported and used to demonstrate the importance of low pressure beneath the ischial tuberosities as an indicator of wheelchair cushion suitability.
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: Garber SL, Rintala DH.
publication: J Rehabil Res Dev. 2003 Sep-Oct;40(5):433-41.
Pressure ulcers are a major complication of spinal cord injury (SCI) and have a significant effect on general health and quality of life. The objectives of this retrospective chart review were to determine prevalence, duration, and severity of pressure ulcers in veterans with SCI and to identify predictors of (1) outcome in terms of healing without surgery, not healing, or referral for surgery; (2) number of visits veterans made to the SCI outpatient clinic or received from home care services for pressure ulcer treatment; and (3) number of hospital admissions and days hospitalized for pressure ulcer treatment. From a sampling frame of 553 veterans on the Houston Veterans Affairs Medical Center SCI roster, 215 (39%) were reported to have visited the clinic or received home care for pressure ulcers (ICD-9 code 707.0 = decubitus, any site) during the 3 years studied (1997, 1998, and 1999). From this sample, 102 veterans met the inclusion criteria for further analyses, 56% of whom had paraplegia. The duration of ulcers varied greatly from 1 week to the entire 3-year time-frame. Overall, Stage IV pressure ulcers were the most prevalent as the worst ulcer documented. Number and severity of ulcers predicted outcome and healthcare utilization. This study illustrates the magnitude of the pressure ulcer problem among veterans with SCI living in the community. Reducing the prevalence of pressure ulcers among veterans with SCI will have a significant impact on the Department of Veterans Affairs’ financial and social resources. Innovative approaches are needed to reduce pressure ulcer risk in veterans with SCI.
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.