Biomedical subjects

A Cliquet

Publications and source records attributed to A Cliquet.

12 recordsLinked to original sources

PubMed2006

Effect of treadmill gait on bone markers and bone mineral density of quadriplegic subjects.

Quadriplegic subjects present extensive muscle mass paralysis which is responsible for the dramatic decrease in bone mass, increasing the risk of bone fractures. There has been much effort to find an efficient treatment to prevent or reverse this significant bone loss. We used 21 male subjects, mean age 31.95 +/- 8.01 years, with chronic quadriplegia, between C4 and C8, to evaluate the effect of treadmill gait training using neuromuscular electrical stimulation, with 30-50% weight relief, on bone mass, comparing individual dual-energy X-ray absorptiometry responses and biochemical markers of bone metabolism. Subjects were divided into gait (N = 11) and control (N = 10) groups. The gait group underwent gait training for 6 months, twice a week, for 20 min, while the control group did not perform gait. Bone mineral density (BMD) of lumbar spine, femoral neck, trochanteric area, and total femur, and biochemical markers (osteocalcin, bone alkaline phosphatase, pyridinoline, and deoxypyridinoline) were measured at the beginning of the study and 6 months later. In the gait group, 81.8% of the subjects presented a significant increase in bone formation and 66.7% also presented a significant decrease of bone resorption markers, whereas 30% of the controls did not present any change in markers and 20% presented an increase in bone formation. Marker results did not always agree with BMD data. Indeed, many individuals with increased bone formation presented a decrease in BMD. Most individuals in the gait group presented an increase in bone formation markers and a decrease in bone resorption markers, suggesting that gait training, even with 30-50% body weight support, was efficient in improving the bone mass of chronic quadriplegics.

Absorptiometry, Photon↗

PubMed2005

Response of the arterial blood pressure of quadriplegic patients to treadmill gait training.

Blood pressure pattern was analyzed in 12 complete quadriplegics with chronic lesions after three months of treadmill gait training. Before training, blood pressure values were obtained at rest, during treadmill walking and during the recovery phase. Gait training was performed for 20 min twice a week for three months. Treadmill gait was achieved using neuromuscular electrical stimulation, assisted by partial body weight relief (30-50%). After training, blood pressure was evaluated at rest, during gait and during recovery phase. Before and after training, mean systolic blood pressures and heart rates increased significantly during gait compared to rest (94.16 +/- 5.15 to 105 +/- 5.22 mmHg and 74.27 +/- 10.09 to 106.23 +/- 17.31 bpm, respectively), and blood pressure decreased significantly in the recovery phase (86.66 +/- 9.84 and 57.5 +/- 8.66 mmHg, respectively). After three months of training, systolic blood pressure became higher at rest (94.16 +/- 5.15 mmHg before training and 100 +/- 8.52 mmHg after training; P < 0.05) and during gait exercise (105 +/- 5.22 mmHg before and 110 +/- 7.38 mmHg after training; P < 0.05) when compared to the initial values, with no changes in heart rate. No changes occurred in blood pressure during the recovery phase, with the lower values being maintained. A drop in systolic pressure from 105 +/- 5.22 to 86.66 +/- 9.84 mmHg before training and from 110 +/- 7.38 to 90 +/- 7.38 mmHg after training was noticed immediately after exercise, thus resulting in hypotensive symptoms when chronic quadriplegics reach the sitting position from the upright position.

Adult↗

PubMed2005

Metabolic and cardiorespiratory responses of tetraplegic subjects during treadmill walking using neuromuscular electrical stimulation and partial body weight support.

STUDY DESIGN: Determination of differences in the cardiorespiratory responses of tetraplegic subjects with incomplete and complete lesions during treadmill gait and endurance exercise provided by neuromuscular electrical stimulation (NMES). Differences between rest and exercise phases were also examined. OBJECTIVES: To compare the cardiorespiratory responses in tetraplegic individuals during endurance exercise in the sitting position and treadmill gait with 30-50% body weight relief, both provided by NMES. SETTING: Rehabilitation Ambulatory at University Hospital, Brazil. METHODS: A total of 31 tetraplegic subjects were evaluated. Individuals were separated into two groups: gait group and endurance exercise group. In the gait group (n=17), the exercise protocol consisted of three different phases: 8 min of rest, 10 min of treadmill walking using NMES and 10 min of recovery. In the endurance exercise group (n=14), the cardiorespiratory test consisted of 8 min of rest, 15 min of quadriceps endurance exercise in the sitting position by NMES and 10 min of recovery. Oxygen uptake (VO(2)), carbon dioxide production (VCO(2)), respiratory exchange ratio (RER), pulmonary ventilation (V(E)) and heart rate (HR) were measured. RESULTS: All parameters increased considerably in the gait group from rest to the walking phase, although individuals with incomplete lesions presented a more pronounced increase than those with complete lesion. In the gait group, for incomplete tetraplegics, the mean VO(2) peak was 0.816+/-0.314 l/min, corresponding to 11.41+/-3.11 ml/kg/min; the mean value for VCO(2) was 0.660+/-0.24 l/min, mean HR was 124.54+/-28.72 bpm and mean V(E) was 28.38+/-6.28 l/min. In the endurance exercise group, for incomplete tetraplegics, the mean VO(2) peak was 0.246+/-0.07 l/min, corresponding to 3.84+/-0.92 ml/kg/min; the mean value for VCO(2) was 0.205+/-0.06 l/min, mean HR was 71.45+/-15.51 bpm and mean V(E) was 11.83+/-2.72 l/min. In the endurance exercise group, smaller differences were observed in all variables from rest to the exercise phase, compared with the large increases observed in the gait group. CONCLUSIONS: These preliminary results have shown that gait training probably improves physical capacity in tetraplegic individuals more than the endurance exercise.

Adult↗

PubMed2005

Energy expenditure during rest and treadmill gait training in quadriplegic subjects.

STUDY DESIGN: The analysis of oxygen uptake (VO(2)) and energy consumption in quadriplegics after 6 months of treadmill gait with neuromuscular electrical stimulation (NMES). OBJECTIVES: To compare metabolic responses in quadriplegics after 6 months of treadmill training, with NMES (30-50% body weight relief), with quadriplegics who did not perform gait. SETTING: Ambulatory of University Hospital, Brazil. METHODS: Quadriplegics were separated into gait and control groups (CGs). On inclusion, all subjects performed VO(2) test. In the gait group (GG) (n=11), the protocol consisted of 8 min of rest, 10 min of treadmill walking using NMES and 10 min of recovery. In the CG (n=10), testing consisted of 8 min rest, 15 min of quadriceps endurance exercise in sitting position with NMES and 10 min recovery. VO(2), carbon dioxide production (VCO(2)) and energy consumption were measured. The GG performed 6 months of treadmill training, using NMES, for 20 min, twice a week. The CG did not practice any activity with NMES, performing conventional physiotherapy only; the CG was stimulated only during the cardiorespiratory test. RESULTS: All parameters increased significantly for the GG: 36% for VO(2) (l/min), 43% for VCO(2) (l/min) and 32.5% for energy consumption (J/kg/s). For the CG, during knee extension exercise, VO(2) increased without changes in the energy consumption (P<0.05); smaller values were obtained for all parameters when compared to those obtained during gait. CONCLUSIONS: Quadriplegic gait was efficient towards increasing VO(2) and energy consumption, which can decrease the risk of cardiovascular diseases.

Adult↗

PubMed2004

Intraoperative localization of an osteoid-osteoma using a gamma probe.

The purpose of this study was to evaluate whether intraoperative nidus detection with a hand-held gamma probe was efficient enough for use as a routine procedure. Thirty-seven patients with osteoid-osteomas were submitted to surgical treatment. The first group consisted of 19 patients submitted to open nidus resection using a hand-held gamma probe as guide. The control group consisted of 18 patients operated on by conventional technique. The procedures were classified as successful if nidus resection could be confirmed by histology or postoperative imaging studies. Patients in the gamma group were followed for a mean of 13 months; patients in the control group for a mean of 39 months. In the gamma group, 17/19 procedures were successful; in the control group, only 12/18 procedures were successful. The gamma probe helped to locate the osteoid-osteoma nidus, and the same probe could be used in various hospitals.

Adolescent↗

PubMed2000

Artificial grasping system for the paralyzed hand.

Neuromuscular electrical stimulation has been used in upper limb rehabilitation towards restoring motor hand function. In this work, an 8 channel microcomputer controlled stimulator with monophasic square voltage output was used. Muscle activation sequences were defined to perform palmar and lateral prehension and power grip (index finger extension type). The sequences used allowed subjects to demonstrate their ability to hold and release objects that are encountered in daily living, permitting activities such as drinking, eating, writing, and typing.

Activities of Daily Living↗

PubMed2000

Artificial sensorimotor integration in spinal cord injured subjects through neuromuscular and electrotactile stimulation.

Spinal cord injured (SCI) subjects lack sensorimotor functions. Neuromuscular electrical stimulation (NMES) systems have been used to artificially restore motor functions, but without proprioceptive feedback, SCI subjects can control NMES systems only when they can see their limbs. In a gait restoration system, the subject looks down to the ground to be aware of where his foot is while in a grasping activity, maximum grip strength is employed regardless of the force that is required to perform tasks. This report focuses on artificial sensorimotor integration. Multichannel stimulation was used to restore motor functions while encoded tactile sensation (moving fused phantom images) relating to artificially generated movements was provided by electrotactile stimulation during walking and grasping activities. The results showed that the sensorimotor integration attained yielded both the recognition of artificial grasp force patterns and a technique to be used by paraplegics allowing spatial awareness of their limb while walking.

Adult↗

PubMed1998

Gait restoration in a spinal cord injured subject via neuromuscular electrical stimulation controlled by an artificial neural network.

Attempts to restore gait in spinal cord injured subjects have stumbled on control difficulties associated to the neuromuscular system's non-linearity and time-variance. Thus, a simple autoadaptive artificial neural network has been devised to control gait swing generation by means of neuromuscular electrical stimulation. Both theoretical and experimental approaches were taken. The computer-based system consisted of a three-layer artificial neural network that read angular data from the hip, knee and ankle joints. The output signal consisted of variations on the applied stimulation pulse width. Surface electrical stimulation was applied to the femoral and peroneal nerves of one leg. Neural network training included off-line supervised learning schemes. The system was tested on a male subject with an incomplete C6-level lesion. Several tests were run to determine whether the off-line trained neural network could correctly control the motion. The effect of on-line learning upon the control performance was also evaluated. The system was found to control the motion with success only at times. Control performance was found to improve in response to the application of on-line learning. Learning stability following on-line learning was found to be satisfactory. In a final test, the artificial neural system had appropriate responses to an initial perturbation, which suggests that further research in this area should be pursued.

Algorithms↗

PubMed1997

Two artificial neural systems for generation of gait swing by means of neuromuscular electrical stimulation.

A three-layer artificial neural network was used for adaptive control of gait swing generated by neuromuscular electrical stimulation (NMES) in a spinal cord injured subject. Network inputs consisted of knee and ankle goniometer signals for System 1, and knee and hip angular data for System 2. Controller output was proportional to changes in applied NMES pulse width (PW). Stimulation was applied to the left femoral and common peroneal nerves. The neural networks were trained off-line and on-line. Network performance was assessed by applying a number of different stimulation PWs and later comparing the resulting motion to a sample good step observed during the same test session. On-line training consisted of negative and positive reinforcement applied at chosen times. Both on-line and off-line training algorithms consisted of an enhanced supervised backpropagation scheme. Performance evaluation results favour the use of System 1 over System 2. Also, a network trained off-line and later submitted to on-line punishment appears to be more reliable (in automatic mode) than the same network after it is submitted to on-line reward or to off-line training alone. Finally, the systems' immediate response to on-line learning was favourable in all cases. Based on the results, a version of System 1 was used to generate walking in the test subject. This test indicated that the system is promising.

Adult↗

PubMed1997

A methodology for definition of neuromuscular electrical stimulation sequences: an application toward overcoming small obstacles.

Neuromuscular electrical stimulation (NMES) is an important tool for research in the rehabilitation of lost movements in spinal cord injured patients. However, for NMES to be used outside the laboratory setup, the stimulation controller needs to be able to cope with challenging environmental conditions. A methodology to allow conversion of any specific motor task used to cope with one of these environmental conditions toward a control algorithm for NMES is proposed. The methodology was used in the definition of a stimulation sequence that allows overcoming small obstacles by the spinal cord injured patient. Simulations have proven the method feasibility, and clinical trials have confirmed these findings. Motor task conversion using the kinematic approach has shown better results than that of muscle activity.

Adolescent↗

PubMed1997

A low-cost instrumented glove for monitoring forces during object manipulation.

A rehabilitation program toward restoring upper limb movements based on neuromuscular electrical stimulation (NMES) depends on closed-loop control performance, which has been limited by the development of sensors for practical daily use. This work proposes a system to obtain force feedback. The system is comprised of a Lycra commercial glove with force sensing resistors (FSR's) attached to the distal phalanxes of the thumb, index and long fingers. After amplification and filtering, the signal is digitized through an analog-to-digital (A/D) converter. The polynomial fitting coefficients for the characteristic curves, obtained during the sensor calibration process, were inserted in the software thus enabling the reading of forces exerted during object manipulation. The system was applied to 30 normal subjects in order to verify its feasibility and to acquire knowledge of the normal hand function. Different ways of grasping have been detected according to the Force versus Time curve pattern and to the fingers predominantly used in grasping. Results have also shown the influence of parameters such as gender, age, hand size, and object weight in the normal function. The system did show efficacy. It was able to determine grasp forces during object manipulation for up to 73% of the studied sample. This is significant since a single glove was used in a wide range of subjects. For best results in medical applications, the glove should be tailored to the particular characteristics of an individual user.

Adolescent↗

PubMed1996

A solution for linearity, stability and frequency bandwidth in PAM electrocutaneous stimulators' isolation interface.

This paper introduces a novel method to isolate low-level from high-voltage circuits and/or channels of PAM electrocutaneous stimulators in neuromuscular electrical stimulation (NMES). The method avoids problems of linearity and polarization stability of optocouplers and narrow bandwidth of isolation amplifiers. Its main parameters are: carrier frequency of rectangular pulses up to 1 MHz and maximum modulating signal (elliptical or triangular envelopes) of 50 kHz. The circuit has low drift, high-voltage isolation, low-power consumption, requires few components, is battery-operated and ideal for microcomputer interface-based applications.

Analog-Digital Conversion↗