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PubMed1989

Cybernetic model of psychophysiologic pathways: II. Consciousness of tension and kinesthesia.

This paper describes a series of experiments directed toward the following questions: a) do signals from musculotendinous receptors reach consciousness?, and b) does feed-forward information of muscular force and expected extent of voluntary movement exist? To answer these questions, data from voluntary compression of springs and strain-gauge have been analyzed in healthy young subjects. By successive elimination of information from other sources, it was possible to verify that receptors in muscles and tendons do signal movement magnitude and muscular tension to the cerebral cortex, and that this information does reach consciousness. There also exists a feed-forward mechanism signalling parameters of voluntary contraction. However, it is unclear whether peripheral, subcortical or intracortical loops are directly involved.

Biofeedback, Psychology↗
PubMed1989

Cybernetic model of psychophysiologic pathways: III. Clinical impairment of tension and kinesthesia.

It is unclear whether peripheral, subcortical or intracortical loops are directly involved between receptors in muscles and tendons and the cerebral cortex in signaling movement magnitude and muscular tension information. Previous experiments have indicated that this information does reach consciousness. Data from voluntary compression of springs and strain-gauge were analyzed in patients with unilateral focal lesions of the cerebral hemispheres. It was found that the perception of signals of muscular tension is abolished by lesions of the contralateral cortex near the central sulcus. It was concluded that the possibility exists of separate cortical projection areas for kinesthetic signals from muscles and from joints.

Brain Diseases↗
PubMed1983

[Continuous frequency analysis (spectral trend analysis) in the evaluation of long-term EEG recordings].

This study demonstrates the possibilities of continuous frequency analysis supporting the evaluation of long lasting EEG recordings which present problems in analysing large amount of data. Avoiding some disadvantages of the usual presentation of power spectra by compressed spectral array compression of the spectral data will be obtained in a more suitable way by sequential plots of the data on the abscissa as time axis. The spectra will be separated in only a few number of frequency bands. A special conversion procedure (linear multiplication of the data within each frequency band by logarithmic calculated factors) provides for the essential enhancement of low spectral power in the upper EEG frequency domain preserving the full dynamic of spectral variations. The efficiency of this spectral trend analysis is shown by two examples: (1) In the study of the variations of cerebral excitability in a patient with epileptic seizures depending on the waking-sleeping-cycle (Fig. 3), and (2) in the documentation of the EEG dynamics in the course of intensive care monitoring. Fig. 5 shows the development of a cerebral autorhythmicity representing reintegration of cerebral function in a patient with severe head injury.

Adolescent↗
PubMed1998

Lightning-associated deaths--United States, 1980-1995.

A lightning strike can cause death or various injuries to one or several persons. The mechanism of injury is unique, and the manifestations differ from those of other electrical injuries. In the United States, lightning causes more deaths than do most other natural hazards (e.g., hurricanes and tornadoes), although the incidence of lightning-related deaths has decreased since the 1950s. The cases described in this report illustrate diverse circumstances in which deaths attributable to lightning can occur. This report also summarizes data from the Compressed Mortality File of CDC's National Center for Health Statistics on lightning fatalities in the United States from 1980 through 1995, when 1318 deaths were attributed to lightning.

Adolescent↗
PubMed1998

Repositioning a slumped person in a wheelchair. A biomechanical analysis of three transfer techniques.

The purpose of this study was to determine the effect of three lifting techniques (unassisted lift, vertically assisted lift, and horizontally assisted lift) and two patient masses (65 kg and 75 kg) on loads acting on the lifter's spine when repositioning a wheelchair bound patient to a more upright sitting position. A static biomechanical model was used in conjunction with ground reaction force and videographic data to estimate compression and shear forces at the lumbosacral (L5/S1) joint. Results indicated that: L5/S1 compression forces associated with both unassisted and assisted transfers were of sufficient magnitude to warrant mechanical assistance; the two person technique with the assistant pushing the legs toward the back of the chair was associated with the lowest spinal loads; and L5/S1 compression forces were significantly greater for the vertically assisted lift compared to the unassisted lift. If a manual transfer is to be performed, the horizontally assisted lift is recommended to minimize loads on the lumbar spine of the lifter.

Adult↗
PubMed2002

Tolerance of the cervical spine to eccentric axial compression.

Cervical spine injury resulting from compressive impact loading is a particularly devastating musculoskeletal injury due to the frequency of neurologic involvement. The objective of this research was to investigate the effect of axial eccentricity on the tolerance of the cervical spine. Two functional spinal unit segments (3 adjacent vertebra and their intervening discs and soft-tissues) were dissected from the lower cervical spine of twenty-four human cadaver cervical spines and randomly assigned to one of three loading groups. The eight specimens were tested to failure in compression, compression-flexion, and compression-extension under displacement control on a high-rate MTS load frame. The resulting six-axis loads were measured and evaluated by injury mechanism (group). Statistically distinct (p < 0.01) injury mechanisms, in terms of measured axial eccentricity, were produced by each of the eccentric axial compression inputs (compression-flexion, compression-extension, and compression). The axial force at failure for the compression and compression-extension loading environments were nearly equal and significantly (p < 0.01) larger (4-times) than their counterpart in the compression-flexion group. Failure data were compared with the neck injury criteria (Nij) recently proposed by the NHTSA using the 50th percentile male and 5th percentile female injury reference values. The compression and compression-extension mechanisms produced Nij values near 1.0. The compression-flexion series resulted in significantly lower Nij values at failure (approx. 0.3, p < 0.01). The results of this study provide tolerance data for the cervical spine subjected to different compressive loading environments and may be used to enhance injury reference computations facilitating neck injury prevention.

Journal Article↗
PubMed2005

Wavelet coding of volumetric medical images for high throughput and operability.

This paper presents a new three-dimensional (3-D) wavelet-based scalable lossless coding scheme for compression of volumetric medical images. Aiming to improve the productivity of radiologists and the cost-effectiveness of the system, we strive to achieve high decoder throughput, random access to coded data volume, progressive transmission, and high compression ratio in a balanced design approach. These desirable functionalities are realized by a modified 3-D dyadic wavelet transform tailored to volumetric medical images and an optimized Rice code of very low complexity.

Algorithms↗
PubMed2006

Octree indexing of DICOM images for voxel number reduction and improvement of Monte Carlo simulation computing efficiency.

The purpose of the present study is to introduce a compression algorithm for the CT (computed tomography) data used in Monte Carlo simulations. Performing simulations on the CT data implies large computational costs as well as large memory requirements since the number of voxels in such data reaches typically into hundreds of millions voxels. CT data, however, contain homogeneous regions which could be regrouped to form larger voxels without affecting the simulation's accuracy. Based on this property we propose a compression algorithm based on octrees: in homogeneous regions the algorithm replaces groups of voxels with a smaller number of larger voxels. This reduces the number of voxels while keeping the critical high-density gradient area. Results obtained using the present algorithm on both phantom and clinical data show that compression rates up to 75% are possible without losing the dosimetric accuracy of the simulation.

Algorithms↗
PubMed1998

Removal of dermal edema with class I and II compression stockings in patients with lipodermatosclerosis.

BACKGROUND: Lipodermatosclerosis is a sequela of deep venous insufficiency and a risk factor for the occurrence of venous leg ulceration. Medical compression stockings facilitate leg ulcer healing and prevent occurrence of ulcers resulting from removal of edema. Although the exact level of compression necessary for removal of dermal edema in patients with deep venous insufficiency has not been established, garments providing high compressive values of 30 to 40 mm Hg have been recommended. Dermal edema can be visualized by high-frequency ultrasonography. OBJECTIVE: We used ultrasound imaging to study whether a lower level of compression (class I 18 to 26 mm Hg vs class II 26 to 36 mm Hg) is effective in removal of dermal edema. This question is important because the use of hosiery with a lower compression class would enhance compliance and enable treatment of patients with mixed arteriovenous disease. METHODS: In 11 patients skin images were obtained with 20 MHz ultrasound from the malleolar region in lipodermatosclerotic skin and corresponding normal skin of the contralateral leg. The ratio of low echogenic pixel number to total pixel number (LEP/TP), which correlates with dermal water, was measured before and after 5 days of applied compression in two treatment courses where classes of compression were switched randomly. Ankle circumference was also measured. RESULTS: We found that LEP/TP was 33% higher in lipodermatosclerotic skin than in the matched normal skin indicating presence of skin edema. Application of class I and II compressive hosiery resulted in LEP/TP decrease by 17% (95% confidence interval, 0.07 to 0.26) and 14% (95% confidence interval, 0.04 to 0.21), respectively, suggestive of dermal edema reduction. No statistically significant difference in efficacy of dermal edema removal between class I and II was found. No changes in ankle circumference after application of both classes of compression was observed. CONCLUSION: Application of light and moderate compression results in a partial edema removal from the dermis in lipodermatosclerosis in the absence of measurable reduction in leg circumference. Class I compression is as effective as class II for elimination of dermal edema. These data indicate that light compression may be a useful modality for patients with deep venous insufficiency and lipodermatosclerosis who are not eligible for treatment with garments having higher compressive forces.

Adult↗
PubMed2004

Evidence-based compression: prevention of stasis and deep vein thrombosis.

OBJECTIVE: To summarize the currently published scientific evidence for the venous flow effects of mechanical devices, particularly intermittent pneumatic compression, and the relation to prevention of deep vein thrombosis (DVT). SUMMARY BACKGROUND DATA: While intermittent pneumatic compression is an established method of DVT prophylaxis, the variety of systems that are available can use very different compression techniques and sequences. In order for appropriate choices to be made to provide the optimum protection for patients, the general performance of systems, and physiological effects of particular properties, must be analyzed objectively. METHODS: Medline was searched from 1970 to 2002, and all relevant papers were searched for further appropriate references. Papers were selected for inclusion when they addressed specifically the questions posed in this review. RESULTS: All the major types of intermittent compression systems are successful in emptying deep veins of the lower limb and preventing stasis in a variety of subject groups. Compression stockings appear to function more by preventing distension of veins. Rapid inflation, high pressures, and graded sequential intermittent compression systems will have particular augmentation profiles, but there is no evidence that such features improve the prophylactic ability of the system. CONCLUSIONS: The most important factors in selecting a mechanical prophylactic system, particularly during and after surgery, are patient compliance and the appropriateness of the site of compression. There is no evidence that the peak venous velocity produced by a system is a valid measure of medical performance.

Bandages↗
PubMed2002

Neuropeptide Y inhibits the hyperexcitability of type A neurons in chronically compressed dorsal root ganglion of the rat.

Our recent data revealed adrenergic sensitivity in chronically compressed dorsal root ganglion (DRG) of rats. As neuropeptide Y (NPY) is a common sympathetic co-transmitter, we investigated the effect of NPY on injured DRG neurons. The expression of NPY Y1 and Y2 receptors and the effect of NPY on chronically compressed DRG neurons were studied using in situ hybridization and extracellular single fiber recording in vitro, respectively. After DRG compression, the expression of Y1 receptor was distinctly increased in large and medium-sized DRG neurons, while Y2 receptor was increased in small DRG neurons. NPY inhibited both the spontaneous activity and the excitatory effect of norepinephrine in injured DRG A-neurons. The results suggest a possibility that NPY may inhibit the hyperexcitability of injured DRG A-neurons via increased Y1 receptor following chronic compression.

Action Potentials↗
PubMed1997

Composition- and history-dependent radial compressive behavior of human atherosclerotic plaque.

Invasive procedures to revascularize occluded blood vessels rely on the mechanical response of the diseased tissue. Failure rates associated with such procedures show the need for improvement. to understand the associated mechanics, the material properties of atherosclerotic plaque should be known; yet data are scant. The purpose of this study was to investigate the different mechanical responses exhibited by plaques with different compositions, focusing specifically on radial compressive behavior. A custom-built experimental system was developed that was fully computer controlled with a broad range of loading capabilities. A temperature-controlled, physiologic specimen bath allowed testing at 37 degrees C. Monotonically loaded specimens showed that plaque behavior was nonlinear under finite deformations. A multiple cycle protocol, executed in two phases, distinguished three types of mechanical response of different plaques. The differences in behavior were associated with histologic differences in plaque composition, and mechanically characterized by different "repeatability" (the stabilization of the cyclic response) and "recoverability" (the second loading phase retracing the first loading phase behavior). Type 1 behavior was categorized by repeatability and recoverability. Type 2 behavior displayed repeatability but only partial recovery during the second loading phase. Recovery was absent in type 3 behavior. The histologic observations demonstrated that calcified tissue was present only in specimens displaying type 1 behavior. Fibrous tissue and part of a modified media (due to disease) were present in specimens displaying type 2 behavior. An atheroma, along with a relatively thin modified media, was present in specimens displaying type 3 behavior. The differences in the maximum stretches attained at the end of phase I loading, the stretch offset from the first to the 15th cycle of phase I loading, and the hysteresis in the first and 15th cycles of phase I loading distinguished the specimen behaviors with statistical significance. These compression data showed that plaques exhibit composition- and history-dependent nonlinear and inelastic responses under finite deformations.

Aged↗
PubMed2001

A compressive gammachirp auditory filter for both physiological and psychophysical data.

A gammachirp auditory filter was developed by Irino and Patterson [J. Acoust. Soc. Am. 101, 412-419 (1997)] to provide a level-dependent version of the linear, gammatone auditory filter, with which to explain the level-dependent changes in cochlear filtering observed in psychophysical masking experiments. In this 'analytical' gammachirp filter, the chirp varied with level and there was no explicit representation of the change in filter gain or compression with level. Subsequently, Carney et al. [J. Acoust. Soc. Am. 105, 2384-2391 (1999)] reviewed Carney and Yin's [J. Neurophysiol. 60, 1653-1677 (1988)] reverse-correlation (revcor) data and showed that the frequency glide of the chirp does not vary with level in their data. In this article, the architecture of the analytical gammachirp is reviewed with respect to cochlear physiology and a new form of gammachirp filter is described in which the magnitude response, the gain, and the compression vary with level but the chirp does not. This new 'compressive' gammachirp filter is used to fit the level-dependent revcor data reported by Carney et al. (1999) and the level-dependent masking data reported by Rosen and Baker [Hear. Res. 73, 231-243 (1994)].

Auditory Perception↗
PubMed2001

Spinal radiation before surgical decompression adversely affects outcomes of surgery for symptomatic metastatic spinal cord compression.

STUDY DESIGN: A retrospective chart review was performed. OBJECTIVE: To determine whether preoperative spinal radiation increases the number of major wound complications in patients with cancer who have symptomatic spinal cord compression. SUMMARY OF BACKGROUND DATA: Many factors have increased the number of patients hospitalized with symptomatic spinal cord compression after spinal irradiation. The surgical management of metastatic spinal cord compression may be complicated by preoperative radiation. METHODS: A retrospective review of 123 patients admitted with symptomatic metastatic spinal cord compression from 1970 through 1996 was conducted. The final study population of 85 patients was separated into three treatment groups: 1) radiation only, 2) radiation followed by surgery, and 3) de novo surgery followed by radiation. RESULTS: The major wound complication rate for patients who had radiation before surgical decompression and stabilization was 32%, or threefold, higher than the 12% observed in patients who had de novo surgery (P < 0.05). No other clinical factor or condition predicted the development of a major wound complication. Patients treated initially with surgery had superior functional outcomes in an analysis stratified by Frankel grade (P < 0.05). Of the ambulatory patients who underwent de novo surgery, 75% remained ambulatory and continent 30 days after treatment, whereas only 50% of those treated with radiation before surgery had similar outcomes. CONCLUSIONS: Spinal radiation before surgical decompression for metastatic spinal cord compression is associated with a significantly higher major wound complication rate. In addition, preoperative spinal irradiation might adversely affect the surgical outcome.

Adult↗
PubMed2001

New technologies in spine: kyphoplasty and vertebroplasty for the treatment of painful osteoporotic compression fractures.

STUDY DESIGN: Literature review. OBJECTIVES: To describe new treatments for painful osteoporotic compression fractures in light of available scientific literature and clinical experience. SUMMARY OF BACKGROUND DATA: Painful vertebral osteoporotic compression fractures lead to significant morbidity and mortality. This relates to pulmonary dysfunction, eating disorders (nutritional deficits), pain, loss of independence, and mental status change (related to pain and medications). Medications to treat osteoporosis (primarily antiresorptive) do not effectively treat the pain or the fracture, and require over 1 year to reduce the degree of osteoporosis. Kyphoplasty and vertebroplasty are new techniques that help decrease the pain and improve function in fractured vertebrae. METHODS: This is a descriptive review of the background leading to vertebroplasty and kyphoplasty, a description of the techniques, a review of the literature, as well as current ongoing studies evaluating kyphoplasty. RESULTS: Both techniques have had a very high acceptance and use rate. There is 95% improvement in pain and significant improvement in function following treatment by either of these percutaneous techniques. Kyphoplasty improves height of the fractured vertebra, and improves kyphosis by over 50%, if performed within 3 months from the onset of the fracture (onset of pain). There is some height improvement, though not as marked, along with 95% clinical improvement, if the procedure is performed after 3 months. Complications occur with both and relate to cement leakage in both, and cement emboli with vertebroplasty. CONCLUSION: Kyphoplasty and vertebroplasty are safe and effective, and have a useful role in the treatment of painful osteoporotic vertebral compression fractures that do not respond to conventional treatments. Kyphoplasty offers the additional advantage of realigning the spinal column and regaining height of the fractured vertebra, which may help decrease the pulmonary, GI, and early morbidity consequences related to these fractures. Both procedures are technically demanding.

Aged↗
PubMedDate not supplied

Activity of enzymes of adenyline compounds metabolism during crush and decompression of muscle tissue. Part II. Adenosine deaminase activity at experimental crush syndrome.

INTRODUCTION: Publications on investigation of crush syndrome pathogenesis, particularly of enzymatic systems upon traumatic toxicosis are rather limited. Such investigations are necessary for opportune diagnosis and definition of a treatment tactic. To replenish this deficiency, the adenosine deaminase level was studied in 12 rat tissues at experimental crush syndrome in vivo. RESULTS: The experimental model of crush syndrome on white rats was induced by crush and decompression of femoral muscle tissue. The crush syndrome influence on activity of adenosine deaminase isoenzymes was investigated in hemisphere, cerebellum, hypothalamus, pituitary body, heart, lung, liver, spleen, kidney, adrenal, as well as in crushed and native muscles. In 2 and 5 hours after compression, the enzyme activity decreased in muscles, lung and heart; increased in hypothalamus; remains near the control value in kidney and spleen. In cerebellum the parameter practically does not vary during 2 hours compression, while increased in 5 hours. In adrenal, liver, pituitary body and hemisphere the data after 5 hours compression approximated the level of control value in account of compensating mechanism. In 48 hours decompression after 2 hours crush, the adenosine deaminase activity becomes higher than control value in hemisphere, hypothalamus, cerebellum, liver, heart, adrenal, intact muscle, lung and kidney; in the crushed muscle and spleen the activity is reduced down to 60% of control value. In 48 hours decompression after 5 hours compression, the enzyme activity is higher than control value in hypothalamus, pituitary body, hemisphere, cerebellum, kidney, adrenal, heart and lung. The activity is reduced in muscles, spleen and liver. CONCLUSION: The level of adenosine deaminase in most of studied tissues differs from the control value depending on compression and decompression time. It is worthy of note that namely during decompression, the enzyme level deviates from the control in the majority of tissues.

Adenosine Deaminase↗
PubMed2003

Standardized 3D documentation for neurosurgery.

OBJECTIVE: Although direct volume visualization is now a standard tool for diagnosis and therapy planning for medical conditions in the brain, its application is normally restricted to radiological workstations. We propose the use of standardized digital video sequences which can be easily ported to mobile computing platforms and thereby to diverse clinical environments. The effectiveness of this approach is demonstrated in the operating room. MATERIALS AND METHODS: Segmented MR data corresponding to neurovascular compression syndrome pathologies was examined with 3D visualization based on tagged volumes. CT-angiography data containing aneurysms close to the skull base was analyzed with volume visualization based on bidimensional transfer functions. Furthermore, automatic adjustment of bidimensional transfer function templates was implemented. An extension of the applied volume visualization tool made it possible to standardize the creation of pathology-specific digital video sequences. RESULTS: Five cases of neurovascular compression syndromes and 4 cases of aneurysms close to the skull base were examined. One-dimensional transfer function templates were successfully applied for the visualization of neurovascular compression syndromes. Automatic adjustment of transfer function templates made it possible to achieve good-quality results for visualization of aneurysms without external adjustment. The resulting digital video sequences were successfully used in the operating room. CONCLUSION: The portability of the 3D video sequences broadens their application spectrum, making them adequate not only for database purposes, but also for surgical support and cooperative environments. Furthermore, the required technical knowledge is encapsulated, making this approach more suitable for clinical applications.

Humans↗
PubMed1988

Selected concepts and controversies in pediatric cardiopulmonary resuscitation.

Although more than 80 years of research in cardiac resuscitation produced many important findings and greatly enhanced our understanding of the arrest state, outcome following pediatric cardiac arrest remains poor. Resuscitation guidelines have recently been published, but they may not reflect optimal therapy. Closed-chest compression-induced cardiac output may be higher in pediatric patients, particularly infants, than that previously reported in adults. To achieve higher cardiac outputs, direct cardiac compression is important; the recommended compression location has therefore been changed based on recent data. The optimal rate of compression, however, is uncertain, so further research is needed. Alternative vascular access sites, such as the endotracheal and intraosseous route for drug administration may permit more rapid drug delivery, but data suggest that a larger epinephrine dose than currently recommended should be used. It may also be helpful to dilute the drug in normal saline before endotracheal administration. Although experimental data suggest that a pure alpha-adrenergic agonist may be beneficial in a cardiac arrest, recent data show that epinephrine remains the drug of choice. Finally, the role of sodium bicarbonate in both the arrest and postarrest setting has become controversial. Recent data suggest that bicarbonate may be detrimental and that therapy of acidosis is best directed at improving perfusion, oxygenation, and ventilation. Alternative forms of therapy for acidosis, such as THAM and dichloroacetate may prove beneficial in the postarrest setting.

Acidosis↗