Pulmonary function testing in spinal cord injury: effects of abdominal muscle stimulation.

The purpose of this study was to assess the effects of applying transcutaneous electrical stimulation to paralyzed abdominal muscles during pulmonary function testing (PFT) of individuals with spinal cord injury (SCI). Ten male subjects with anatomical level of SCI between C5-T7 were studied. Subjects performed PFTs with and without electrical stimulation delivered to the abdominal muscles. Subjects with the lowest percentage of predicted expiratory volumes and flows demonstrated the greatest improvement when electrical stimulation was delivered during forced expiration. The overall increases seen in percent of predicted for the study sample were 23 percent for forced vital capacity (FVC), 16 percent for forced expiratory flow in 1 s (FEV1), and 22 percent for peak expiratory flow rate (PEF). Contractions of paralyzed expiratory muscles in response to electrical stimulation during the performance of PFT maneuvers can significantly improve FVC, FEV1, and PEF in some individuals with SCI.

Isotopic ratio analysis in residential lead-based paint and associated surficial dust.

OBJECTIVES: This investigation assessed the contribution of lead in lead-based paint (7 samples) to lead-laden dust (8 samples) in a single suburban vacant residence using isotopic ratio analysis. METHODS: Interior/exterior lead-based paint surface concentration was measured by X-ray fluorescence while dust and scrapings were analyzed chemically for total lead content and by mass spectrometry for the associated isotopic ratios. RESULTS: Four out of 5 comparisons of paint (7 samples) and dust (8 samples) for a given location did not match isotopically. In the one location where the isotopic ratio of the paint and dust samples matched closely, some portions of the paint were not intact. One explanation for the isotopic ratio match is that the dust sample may have actually been contaminated with paint flecks. This explanation appears likely since the isotopic ratio for the lead in the dust and paint sample were not in the modern average range of US environmental lead, strongly indicating a local point source of the lead in this dust sample, namely the paint at this location. Lead dust samples whose isotopic ratio lies in the modern average range for US environmental lead cannot be correlated to the paint which is beneath them, since the isotopic ratio of lead in the dust may actually be a composite of many sources of lead over time, as suggested by an isotopic ratio in the modern average range. CONCLUSIONS: From the samples from this one house, the data dispute the contention that intact lead-based paint chalks and creates lead-contaminated dust on its surface. While leaded household dust may contribute to children's lead exposure, intact paint need not contribute to surficial lead-laden dust. Isotopic ratio measurements can be useful for point-source determination by virtue of sample match and by placement of the ratio on the spectrum of isotopic ratio values for lead. Point-source assessment based on isotopic ratio was either strengthened or weakened by placement outside or within the average range for US environmental lead, respectively.

Cough in spinal cord injured patients: the relationship between motor level and peak expiratory flow.

Pulmonary complications remain a major cause of morbidity and mortality in patients with higher level spinal cord injury. Neurologically intact individuals can cough in order to clear their air passage of lung secretions and foreign material. Patients with higher level cord injuries, with paralysis of the trunk and abdominal muscles, may not have the ability to generate an effective cough. If coughing is dependent on a caregiver, these patients will cough with reduced frequency. Because the innervation to the muscles involved in cough consists of nerves that arise from varying levels of the spinal cord, some patients with spinal cord injury have partial control over these muscles and thus can cough, though with reduced efficacy. Two hundred patients with varying levels of spinal cord injury were studied to determine if motor level and cough ability are correlated. Cough efficacy was measured using a peak expiratory flowmeter while patients were seated at 90 degrees. We concluded that there is indeed a direct relationship between motor level and peak expiratory flow produced during coughing.

Electrical stimulation and biofeedback effect on recovery of tenodesis grasp: a controlled study.

OBJECTIVE: Evaluate the effectiveness of electrical stimulation and biofeedback on the recovery of tenodesis grasp in tetraplegic individuals during the initial phase of acute rehabilitation. DESIGN: A 2 x 2 block design was used with subjects randomized to treatment groups. Forty-five subjects completed the study. SETTING: Inpatient occupational therapy department. SUBJECTS: Inpatients with tetraplegia, first admission for rehabilitation after an acute spinal cord injury. INTERVENTIONS: The four treatment groups were: conventional treatment, electrical stimulation, biofeedback, and combined electrical stimulation and biofeedback. The treatment period was between 5 and 6 weeks. MAIN OUTCOME MEASURES: Manual muscle testing and scoring of activities of daily living performance by a blinded evaluator. RESULTS: All four treatment groups showed improvements. No treatment group was superior to the others. CONCLUSIONS: Biofeedback and electrical stimulation alone or in combination offer no advantages over conventional rehabilitation treatment of wrist extensors in tetraplegic patients after spinal cord injury.

Ventilatory assistance using electrical stimulation of abdominal muscles.

Nine neurologically intact subjects were studied to demonstrate the feasibility of stimulating the muscles of expiration during, and in synchrony with, naturally occurring breathing. A breath-by-breath analysis showed that both tidal volume and the frequency of respiration could be increased during periods of electrical stimulation. A single subject with complete spinal cord injury was studied to eliminate the possibility that the results from the normal subjects could be attributed entirely to either subconscious or conscious volitional response to the stimulation. The results provide a basis for future studies with patients in borderline ventilatory failure.

Cough in spinal cord injured patients: comparison of three methods to produce cough.

Pulmonary complications are the major causes of morbidity and mortality for persons with cervical spinal cord injury. Diminished ability to cough constitutes a major contribution to the high incidence of pulmonary morbidity in this population. This article reports preliminary results for a new technique for providing assisted cough in this population. In this study, efficacy of cough (as measured by peak expiratory flow rate) was measured under three conditions: volitionally with no assistance, with manual assist of a therapist, and with electrical stimulation of abdominal muscles. Coughs produced by electrical stimulation were approximately as effective as manually assisted coughs. The results suggest this technique is worthy of more detailed study and may be a potentially effective new modality for assisting spinal cord injured persons to clear their airways.

Ground reaction forces during termination of human gait.

This is the first published report of the ground reaction forces during gait termination. Two mechanisms appear to be used to stop walking: increased braking forces and decreased push-off force. There appears to be a short interval of time during the gait cycle in which a decision to take an additional step is to be made.

Neuromuscular stimulation in spinal cord injury. II: Prevention of secondary complications.

The spinal cord injured patient has been the focus of clinical and research efforts to restore functional movement and to obtain therapeutic benefits by electric stimulation of upper motor neuron paralyzed muscles. This review article treats developments in this field from 1983 to 1990. Efforts have been directed to restoring ventilatory and bladder function, and to preventing secondary complications. Electric stimulation for improving ventilatory function has had reasonable success, and systems are commercially available. Electric stimulation for improving bladder function remains in the research stage in the US, although it has had some clinical success reported in Europe. Electric stimulation techniques to prevent or treat secondary complications have been applied to pressure ulcers, deep-venous thrombosis, contractures, spasticity, deconditioning due to lack of exercise, and muscle atrophy. Therapeutic electric stimulation techniques are largely research techniques. Much additional work remains to be done to solve the difficult problems associated with applying this technology in the treatment of patients with spinal cord injury.

Neuromuscular stimulation in spinal cord injury: I: Restoration of functional movement of the extremities.

The spinal cord injured patient has been the focus of clinical and research efforts to restore functional movement and obtain therapeutic benefits by electric stimulation of upper-motor-neuron paralyzed muscles. Our review articles treat developments in this field from 1983 to 1990. Efforts have been directed to restoring hand function, standing, and walking (covered in part I), as well as prevention of secondary complications through ventilatory function, bladder function, and achieving therapeutic effects of electric stimulation (covered in Part II). The technology for hand function, standing, and walking is used primarily in the research laboratory, as clinical applications are minimal. Much work remains to be done to solve the difficult problems associated with applying this promising technology to spinal cord injury.

Lower extremity applications of functional neuromuscular stimulation.

Functional electrical stimulation (FES) applications in the lower extremity are common in research laboratories, but clinical applications are minimal. This review summarizes current knowledge with respect to clinical application. When electrical stimulation is used in clinical applications for functional movement such as standing and walking, it is typically applied in an open-loop manner; a predetermined stimulus pattern is delivered regardless of the consequences of the actual movement. Few clinical applications of FES involve closed-loop control because of the numerous difficulties involved in its application. As with any volitional muscle contraction, electrically stimulated muscle contractions will exhibit fatigue. Although the dynamics of fatigue may differ, electrically stimulated muscle contractions cannot be continuously sustained, and if the duty cycle is too severe, even alternating periods of rest and contraction cannot be sustained at a constant force level. The exact nature of fatigue is highly specific to the past history of the individual muscle and to the individual subject. Despite their intricate detail, quantitative modeling studies have not yet been applied extensively to clinical applications. Present implantable systems are not yet a viable option for clinical application. It is not clear whether more success with surface or percutaneous systems must first be achieved to justify implantation or whether greater improvements in implantable technology and surgical protocols are needed before implantable systems will become practical. It is clear that almost any reasonably designed stimulation protocol will increase muscle bulk. The existence of other therapeutic benefits and their cost/benefit ratios remain to be fully established. It is possible to stand through bilateral stimulation of the quadriceps. Using surface electrodes, this technique is achievable in any physical therapy clinic having minimal expertise in neuromuscular stimulation. FES-aided standing must be conducted as a research project with a protocol approved by the local institutional review board, as there are currently no FDA-approved stimulation devices for standing. Multichannel FES systems are not currently available for clinical application in the United States. This may change if the "Parastep" system receives FDA approval. Percutaneous and implanted systems are years away from commercialization and clinical availability. Hybrid systems, based primarily on the reciprocating gait orthosis (RGO), are presently the only clinically available form of walking that includes some form of FES assistance. The costs and benefits of adding FES to the RGO and the long-term user acceptance rate for these systems remain to be determined.

Estimating the user population of a simple electrical stimulation system for standing.

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.

Functional neuromuscular stimulation for standing after spinal cord injury.

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.

Analysis of standing up and sitting down in humans: definitions and normative data presentation.

A formal definition of human standing up and sitting down movements based on sagittal plane goniometric and force plate data from 20 normal subjects is presented. This definition is comparable to the established gait cycle diagram, and consists of defined characteristic events and relative time intervals between them. The characteristic events are selected primarily on changes in ground reaction forces. The terminology proposed may be valuable for introducing more formalized and standardized reporting of both qualitative and quantitative studies in both normals and in patients. This presentation is directed toward the process of defining generally acceptable standards for human standing up and sitting down movements.

Coactivation of the hamstrings and quadriceps during extension of the knee.

The electromyographic activities of six muscles of the thigh were recorded, using bipolar surface electrodes, during active extension of the knee by six healthy men. The signal amplitudes were normalized to those recorded during isometric maximum voluntary contractions. Extension of the knee from 90 to 0 degrees (full extension) was performed at the rate of 10 degrees per second with the leg unimpeded and with weights of 1.8, 3.6, 5.4, or 7.2 kilograms attached to the ankle. The hamstrings were found to coactivate with the quadriceps during the terminal phase of extension. Coactivation of all three hamstrings was found to occur at joint angles of as much as 9 degrees, with the maximum at full extension of the knee and the strength of the signals ranging to as much as 20 per cent. The signals of all of the flexors and extensors increased with increasing loads on the ankle and, with the exception of the rectus femoris at 9 degrees of flexion, they also increased as the knee extended. The results of this study support the hypothesis that the hamstrings function synergistically with the anterior cruciate ligament to prevent the anterior tibial displacement that is produced by active contraction of the quadriceps in the terminal degrees of extension of the knee. This information is important for the physical conditioning of healthy individuals in preparation for athletic endeavors. Furthermore, if coactivation of the hamstrings with the quadriceps is mediated by sensors other than, or in addition to, those of the anterior cruciate ligament, then strengthening of the hamstrings appears to be an important adjunct to rehabilitation programs after repair or reconstruction of that ligament.

Standing the spinal cord injured patient by electrical stimulation: refinement of a protocol for clinical use.

Standing by functional neuromuscular stimulation can be obtained in a select subpopulation of spinal cord injured individuals. This technology has not yet been made available to patients on a clinical basis. The methodology for a simple two-channel protocol is described in detail, including biomechanics, stimulator design, and muscle response to stimulation. This protocol shows reasonable promise of successful clinical implementation in the future. Results over a five-year period are presented which include data on 21 patients. Estimates of the potential user population of this protocol is 10 percent of the paraplegic population.

Rehabilitation technology for standing and walking after spinal cord injury.

The purpose of this paper is to review the rehabilitation technology available for standing and walking by the spinal-cord injured. Existing aids for standing and walking and those aids under development in research laboratories are discussed. One conclusion is that therapeutic and perhaps functional standing could be achieved in a greater number of individuals using existing technology; however it must also be realized that some barriers still exist which prevent various technologies from being more widely used. Studies which measure the benefits of standing, and more fully establish minimum standing times to achieve these benefits, are needed. Standing is a necessary component of many tasks, and it is unlikely single type of standing aid is likely to perform adequately in every situation that requires standing. Therefore it may be prudent to have a variety of standing aids available to patients.

Time-course studies of the distribution of [1-14C]acrylonitrile in rats after intravenous administration.

Intravenous injection of acrylonitrile (ACN) causes adrenal hemorrhagic necrosis. ACN and its metabolites react with glutathione and bind covalently with macromolecules. Hence the purpose of this investigation was to measure the distribution and covalent binding of radiolabel derived from [1-14C]ACN in order to determine whether binding of ACN or its metabolites may be implicated in the pathogenesis of ACN-induced adrenal injury. Following intravenous injections of ACN, concentrations of total radiolabel were highest in the blood, liver, duodenum, kidneys, and adrenals. Except for blood, there was a time-dependent decrease in total radiolabel in these tissues. Compared with other major organ systems, the levels of covalently bound radiolabel were lower in the adrenal glands. These results do not support a role of covalent binding of ACN or its metabolites in the adrenal toxicity of ACN, but suggest that the initial high concentrations of total radiolabelled compounds derived from ACN could play a role in the action of ACN on the adrenal glands.

Characterization and control of muscle response to electrical stimulation.

The maintenance of upright posture in neurologically intact human subjects is mediated by two major nervous pathways. The first, leading from the cerebral cortex through the spinal cord to motor neurons, activates muscles which produce postural movements. The second, leading from various sensory organs to higher centers, provides sensory feedback regarding the postural state. The path through the spinal cord is no longer intact in victims of spinal cord injury and loss of normal control of muscle activity results. Functional neuromuscular stimulation (FNS) has been shown as a feasible method for obtaining muscle contraction in paraplegics and has been proposed as a means for control of antero-posterior sway to make upright posture possible for these individuals. Before muscle can be controlled through the use of FNS, the response of muscle to electrical stimulation must be understood. In past studies, linear control theory has been applied to the analysis of this response and to the testing of various controllers. The aim of this study was to demonstrate some control issues in FNS using linear control theory, as it applies to electrical stimulation of muscle for stabilization of posture. The linearity of the muscle response was improved through closed-loop control using pole compensation techniques. The excess phase shift of the system due to the time delay in the muscle response, however, limits the ability to increase the open-loop gain in order to obtain improved performance. A suggestion for further study is the application of this methodology for uses in posture control.