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PubMed1989

A comparative study of methods for establishing load handling capabilities.

There has been much effort in recent years to quantify manual handling capabilities. Four main techniques have been used to this end; biomechanical modelling; the measurement of intra-abdominal pressure; psychophysics; and metabolic/physiological criteria. The aim of this study was to compare quantitatively the data produced from the first three techniques. The comparisons were limited to bimanual, sagittal plane lifting, which of all manual handling activities has been studied the most comprehensively, except that pushing and pulling data were compared from the psychophysics and intra-abdominal pressure ('force limits') databases. It was found that the data from 'force limits' proposed weights for bimanual lifting in the sagittal plane which [corrected] are lower than those reported to be psychophysically acceptable except for lifting close to and around the shoulder. The closest agreement between the databases was for lifting from an origin above knuckle height. The 'force limits' data were found to propose weights of lift which are at a minimum when lifting with a freestyle posture from the floor whereas the psychophysical technique proposes weights which are at a maximum when lifting from the floor. The psychophysical data were found to generate compressive forces at L5/S1 according to a static sagittal plane biomechanical model about 10% in excess of the NIOSH action limit (NIOSH 1981) when lifting from the floor, although over other lifting ranges the compressive forces were less than the NIOSH action limit. Lifting the 'force limits' weights generated compressive forces which were on average 55% less than AL (range 45 to 60%) when lifting in an erect posture. The data for pushing according to the psychophysical and 'force limits' database showed good agreement, but for pulling the 'force limits' weights were considerably greater than those selected psychophysically. The implications of these findings are discussed.

Adult↗
PubMed2003

Novel clustering algorithm for microarray expression data in a truncated SVD space.

MOTIVATION: This paper introduces the application of a novel clustering method to microarray expression data. Its first stage involves compression of dimensions that can be achieved by applying SVD to the gene-sample matrix in microarray problems. Thus the data (samples or genes) can be represented by vectors in a truncated space of low dimensionality, 4 and 5 in the examples studied here. We find it preferable to project all vectors onto the unit sphere before applying a clustering algorithm. The clustering algorithm used here is the quantum clustering method that has one free scale parameter. Although the method is not hierarchical, it can be modified to allow hierarchy in terms of this scale parameter. RESULTS: We apply our method to three data sets. The results are very promising. On cancer cell data we obtain a dendrogram that reflects correct groupings of cells. In an AML/ALL data set we obtain very good clustering of samples into four classes of the data. Finally, in clustering of genes in yeast cell cycle data we obtain four groups in a problem that is estimated to contain five families. AVAILABILITY: Software is available as Matlab programs at http://neuron.tau.ac.il/~horn/QC.htm.

Algorithms↗
PubMed2006

Adaptive threshold-based block classification in medical image compression for teleradiology.

Telemedicine, among other things, involves storage and transmission of medical images, popularly known as teleradiology. Due to constraints on bandwidth and storage capacity, a medical image may be needed to be compressed before transmission/storage. Among various compression techniques, transform-based techniques that convert an image in spatial domain into the data in spectral domain are very effective. Discrete cosine transform (DCT) is possibly the most popular transform used in compression of images in standards like Joint Photographic Experts Group (JPEG). In DCT-based compression the image is split into smaller blocks for computational simplicity. The blocks are classified on the basis of information content to maximize compression ratio without sacrificing diagnostic information. The present paper presents a technique along with computational algorithm for classification of blocks on the basis of an adaptive threshold value of variance. The adaptive approach makes the classification technique applicable across the board to all medical images. Its efficacy is demonstrated by applying it to CT, X-ray and ultrasound images and by comparing the results against the JPEG in terms of various objective quality indices.

Algorithms↗
PubMed1999

Extraosseous extension of vertebral hemangioma, a rare cause of spinal cord compression.

STUDY DESIGN: Case report. OBJECTIVE: To illustrate a rare cause of thoracic spinal cord compression, its diagnosis, and its management. SUMMARY OF BACKGROUND DATA: Asymptomatic vertebral hemangiomas are common, but extraosseous extension causing spinal cord compression with neurologic symptoms is rare, and few cases appear in the English-language literature. METHOD: A previously asymptomatic 63-year-old man sought medical attention for acute back pain and thoracic myelopathy of 6 week's duration. Magnetic resonance imaging confirmed the presence of a mass in the T10 vertebral body with paravertebral and intracanalicular extension contributing to cord compression. Decompression and reconstructive surgery were performed and radiotherapy administered after surgery. Preoperative angiography was not performed because of the patient's rapidly progressive neurologic deterioration and the consideration that the differential diagnosis of vertebral hemangioma was less likely. RESULTS: The diagnosis of benign capillary hemangioma was made histologically. Neurologic recovery was complete except for minor residual sensory changes in the legs. At follow-up 10 months after surgery the patient had returned to his usual active life and motor mower repairing business. CONCLUSION: Extraosseous extension of vertebral hemangiomas is a rare cause of thoracic spinal cord compression. As such, the available data are derived from reports based on series involving only a small number of cases, rather than on results of randomized controlled trials. Those causing progressive neurologic symptoms should be surgically decompressed, with the specific procedure determined by the extent and site of the lesion. Preoperative angiography is recommended, but embolization is not always necessary or even possible. Postoperative radiotherapy is recommended when tumor removal is subtotal.

Angiography↗
PubMed2003

Spatial-temporal display of colour-flow ultrasound for the assessment of the effects of intermittent pneumatic compression in limbs.

Colour-flow M-mode ultrasonography in three dimensions (two spatial, one temporal) was used to assess the effects of intermittent pneumatic compression on the blood flow velocities in the common femoral vein and artery. The linear array of a standard 3-D system was held in place over the vessels, to record while a calf and thigh cuff compressed to 60 mmHg. The data was reconstructed in 3-D and, subsequently, sliced in different planes. The technique effectively demonstrated the emptying of distal veins during compression, and hyperaemia in the artery on deflation, in the coronal and sagittal planes. Reconstructions of this type may be of use in visualising the distribution of flow changes within blood vessels.

Acute Disease↗
PubMedDate not supplied

Current issues in cardiopulmonary resuscitation.

Current Advanced Cardiac Life Support (ACLS) guidelines and emergency medical services (EMS) clinical protocols usually recommend immediate defibrillation for victims of out-of-hospital cardiac arrest who have ventricular fibrillation (VF). However, animal studies and results from a small number of clinical investigations now suggest that a short period of chest compressions or ACLS procedures delivered before defibrillation may improve the outcome of patients with prolonged VF. Although the basic science and clinical data supporting a chest-compression-first procedure are compelling, large, multicenter randomized trials are still necessary to determine whether such protocols do indeed improve outcome. In current EMS dispatch practice, traditional cardiopulmonary resuscitation (CPR) instructions are given when needed to bystanders who report a possible cardiac arrest. Recent literature has shown that in certain circumstances, CPR instructions involving chest compressions alone may be given more quickly and can yield an equivalent, if not better, chance of survival. Although this practice is controversial, the general consensus is that any CPR is better than none at all. Therefore, telephone CPR protocols that recommend the immediate initiation of chest compressions may be preferred, particularly for callers who have no previous training in CPR.

Advanced Cardiac Life Support↗
PubMed1989

An instrument for monitoring the force applied by breast compression devices on mammography x-ray sets.

Automatic breast compression devices are commonly fitted to mammographic x-ray sets. The force exerted by these compression devices should be limited and periodically checked. This article describes the design and construction of an instrument for the routine assessment of the force applied by breast compression devices on mammography x-ray sets. Results obtained on four different mammography x-ray units are presented. In addition, data on the effect of compression plate design on compression force is given for one unit. The instrument has proved to be a simple and quick method of monitoring the force applied by the compression plates on mammographic x-ray units.

Female↗
PubMed2001

A method to study lumbar spine response to axial compression during magnetic resonance imaging: technical note.

STUDY DESIGN: A magnetic resonance imaging (MRI)-compatible device was developed to apply calibrated compression loads to the lumbar spine during imaging. Experiments were performed to establish a protocol to measure lumbar load-response and estimate muscle-force contribution to spinal load. OBJECTIVE: To develop experimental methodology for direct study of lumbar spine response to compression load. SUMMARY OF BACKGROUND DATA: Most lumbar MRI scans require subjects to lie relaxed and supine, but spinal stenosis has been demonstrated to increase during moderate compressive loading. Several devices have been used to load the spine during MRI, but they could not maintain and/or change calibrated loads during MRI experiments. Furthermore, artifact from viscoelastic creep during imaging was not considered. METHODS: An MRI-compatible spine compression unit with pneumatic load elements was developed to produce calibrated compression loads. Young healthy men were loaded with 140% body weight for up to 10 minutes to establish an appropriate test protocol. Muscle force contribution to spinal load was estimated from electromyography experiments. RESULTS: The spine compression unit produced specified loads +/- 29 N (standard deviation). Spine viscoelastic creep reached steady state by 6.5 minutes, leaving 3.5 minutes for image acquisition. The subjects could support 1.0 body weight for the requisite 10 minutes. Muscle compressive force estimates were only 135 N during application of 1.4 x body weight external compression load; thus, internal muscle forces during supine spine compression could be neglected. CONCLUSIONS: The lumbar load/image protocol fits within the time constraints of creep deformation and subject endurance. These methods allow acute lumbar mechanical response measurements during loading.

Adult↗
PubMed2006

Knee joint position sense in compressive myelopathy.

STUDY DESIGN: The knee joint position sense (JPS) and kinesthesia were measured in patients with compressive myelopathy. OBJECTIVES: To find out how the knee JPS and kinesthesia are useful to evaluate lower limb function in patients with compressive myelopathy. SUMMARY OF BACKGROUND DATA: No previous reports have been written on the quantitative analysis of knee joint proprioception in myelopathy patients. METHODS: Twenty-one compressive myelopathy patients with a mean age of 64 years were studied. The measured values of JPS and kinesthesia were examined in relation to the following: lower limb function and central motor conduction time (CMCT). RESULTS: Inaccurate angles of the knee JPS in patients with severe walking disability were significantly larger than those in patients with mild disability. Inaccurate angles of the knee JPS in patients with severe sensory disturbance were significantly larger than those in patients with mild disturbance. CMCT showed a significant correlation to the knee JPS. CONCLUSIONS: The knee JPS was useful to evaluate lower limb function in patients with compressive myelopathy.

Adult↗
PubMed1998

Clinical Validation of Digital Image Compression Levels for Fetal Echocardiograms for Telemedicine.

BACKGROUND: Digital telephone transmission of dynamic fetal echocardiographic sequences requires wide bandwidths. To reduce the transmission of nonessential information present in echocardiographic images, compression algorithms have been used and validated for adult echocardiography. The level of compression that retains all diagnostic clinical information must be determined and validated for fetal echocardiographic studies. The purpose of this study was to validate levels of image compression that are diagnostic for fetal echocardiography. METHODS: Twenty previously recorded fetal echocardiograms representing two normal and 18 congenitally abnormal hearts were looped, digitized, and compressed at differing ratios. Images were reviewed in a blinded manner by four experts. Images were scored for diagnosis, diagnostic quality, and technical quality. RESULTS: Forty-four images were viewed. Experts correctly diagnosed 87% of images. There were no images of unacceptable diagnostic quality at a compression ratio of 300 (0%) and 2% at compression ratio of 600:1. CONCLUSIONS: Digital image compression of 300:1 was diagnostic for fetal congenital heart diseases with a variety of defects using cine-looped images. These data support the use of compressed fetal images for telephone transmission with a low bandwidth.

Journal Article↗
PubMed1977

Carpal tunnel syndrome: report of 430 operations.

Analyzed are data on 430 operations in 326 patients for median nerve compression at the wrist. Follow-up data from a patient self-evaluation questionnaire were available for 71% of patients. Incidence was highest in the fifth and sixth decades of life, and 65% of patients were female. For most patients, symptoms were worse at night or with excessive hand use or both. Self-evaluation questionnaires showed total relief of symptoms after operation in 51% of cases, 75% or greater improvement in 31%, and 50% or greater improvement in 10%. The dominant hand was more severely involved in two thirds of the patients and 78% of patients had occupations involving considerable use of their hands, suggesting that an occupational factor might be involved in the genesis or aggravation of median nerve compression.

Adolescent↗
PubMed2003

Enhanced umbilical blood flow during acute hypoxemia after chronic umbilical cord compression: a role for nitric oxide.

BACKGROUND: The continuing incidence of intrapartum morbidity may be partly due to antenatal compromise, which influences the fetal defense to labor and delivery. We have shown that antenatal exposure of the ovine fetus to partial compression of the umbilical cord suppresses femoral vasoconstriction during subsequent acute hypoxemia through elevated nitric oxide (NO) activity. This study investigated whether elevated NO activity in cord-compressed fetuses enhanced the vasodilator response to hypoxemia in circulations in which blood flow is known to increase during acute hypoxemia, such as the umbilical vascular bed. METHODS AND RESULTS: Fifteen fetal sheep were chronically instrumented between 117 and 120 days of gestation with vascular catheters and an umbilical flow probe. In 8 of these fetuses, umbilical blood flow was reduced by 30% for 3 days between 125 and 128 days. The remaining 7 fetuses acted as sham-operated controls. Between 2 and 7 days after umbilical cord/sham compression, fetuses were exposed to 2 episodes of acute hypoxemia, on separate days, during infusion with either saline or treatment with a combination of NG-nitro-l-arginine methyl ester and sodium nitroprusside. The data show that umbilical cord compression significantly enhances the umbilical hyperemia through NO-dependent mechanisms during a subsequent episode of acute hypoxemia. CONCLUSIONS: Increased fetal NO activity after chronic cord compression has opposing effects in circulations that either constrict or dilate during subsequent acute hypoxemia. The data imply that antenatal compromise switches the fetal strategy to withstand episodes of subsequent acute hypoxemia of the type that may occur during labor and delivery from a reliance on vasoconstrictor mechanisms to those promoting NO-dependent vasodilation.

Acute Disease↗
PubMed1993

Hydrational and intrinsic compressibilities of globular proteins.

Partial compressibilities of globular proteins in water are reviewed. Contribution of hydrational and of intrinsic compressibilities to experimental partial quantity have been evaluated from ultrasonic data using two independent methods: (a) additive calculation of the hydrational contributions of the surface atomic groups and (b) an analysis of correlation between partial compressibility and molecular surface area. The value (14 +/- 3) X 10(-6) bar(-1) for the isothermal compressibility coefficient of the protein interior at 25 degrees C was obtained as an average value for variety of globular proteins. This value is similar to that of solid organic polymers. Possible relaxation contribution to partial compressibility is roughly estimated from comparison of thermodynamic with x-ray data on protein compressibility. The average compressibility of water in the hydration shell of proteins was found to be 35 X 10(-6) bar(-1), which is 20% less than that of pure water.

Animals↗
PubMed1996

Identification of sequence motifs causing band compressions on human cDNA sequencing.

In order to characterize DNA sequences leading to band compressions in an automated dideoxy-DNA sequencing system which uses fluorescent dye primers, we compiled DNA sequences at compression sites from accumulated sequence data of human cDNAs (about 205 kb in total length). The results clearly showed that almost all the 3'-end regions at the compression sites (> 98%) carried two types of common sequence motifs. The predominant one (about 68%) contained a sequence of 5'-Y'GN1-2AR'-3' (Y' and R': pyrimidine and purine residues capable of base pairing). The remainder (about 32%) carried a hairpin motif with a relatively stable GC-rich stem (> or = 3 bp) connected by a loop consisting of 3 or 4 nucleotides. The occurrence of compressions at these motif sites was further confirmed by using synthetic DNAs with random sequences (about 58 kb in total length). Since DNA sequences at compression sites analyzed so far shared either of the type of motifs in the sequencing system employed here, it was possible to predict the nucleotide residue to be located at a compression site by carefully checking the sequence preceding the site.

Artifacts↗
PubMed1999

Vertebral synovial osteochondromatosis with compressive myelopathy.

STUDY DESIGN: A case report of vertebral synovial osteochondromatosis with compressive myelopathy. OBJECTIVES: To describe the clinical, radiologic, and histopathologic features of vertebral facet synovial osteochondromatosis with compressive myelopathy. SUMMARY OF BACKGROUND DATA: There has been only one previously reported case of synovial osteochondromatosis affecting the vertebral facet joint and no previous report of associated compressive myelopathy. METHODS: The case history, radiology, surgical findings, and histopathology are reviewed. RESULTS: Vertebral facet synovial osteochondromatosis is a potential and readily manageable cause of spinal cord compression. CONCLUSIONS: Synovial osteochondromatosis of the vertebral facet joint should be considered as a cause of compressive myelopathy.

Chondromatosis, Synovial↗
PubMed2003

[Experimental study on the viscoelastic properties of cancellous bone of the os calcaneus, os lunatum and os capitalum].

We have researched the viscoelastic properties of the cancellous bones of the os calcaneus, os lunatum and os capitalum. The compressing stress relaxation experiment and the creep experiment in the vertical, horizontal and 45 degree directions on the os calcaneus were performed. The data and curve of the compressing stress relaxation and creep were obtained. By masing regression analysis we worked out the compressing reduced stress relaxation and creep functions and curves. The results show that the quantities of compressing stress relaxation and creep of the calcaneus in the vertical direction are larger than those in the other two directions. The initial quantities of creep of the os capitalum are larger than those of the os lunatum, and there are no significant different between the quantities of stress relaxation of the cancellous bones of the os lunatum and os capitalum.

Adult↗
PubMed2000

Effects of increased renal parenchymal pressure on renal function.

OBJECTIVE: Acute renal failure is seen with the acute abdominal compartment syndrome (AACS). The cause of acute renal failure in AACS is thought to be multifactorial, including increased renal venous pressure, renal parenchymal pressure (RPP), and decreased cardiac output. Previous studies have established the role of renal venous pressure as an important mediator of this renal derangement. In this study, we evaluate the role of renal parenchymal compression on renal function. METHODS: Two groups of swine (20-26 kg) were studied after left nephrectomy and placement of a renal artery flow probe and ureteral cannula. Two hours were allowed for equilibration, and an inulin infusion was begun to calculate inulin clearance as a measurement of glomerular filtration. In group 1 animals (n = 6), RPP was elevated by 30 mm Hg for 2 hours with renal parenchymal compression. RPP then returned to baseline for 1 hour. In group 2 (n = 6), the RPP was not elevated. The cardiac index, preload, and mean arterial pressure remained stable. Blood samples for plasma renin activity and plasma aldosterone were taken at baseline and at hourly intervals. RESULTS: Elevation of RPP in the experimental group showed no significant decrease in renal blood flow index or glomerular filtration when compared with control animals. There were no significant elevations of plasma aldosterone or plasma renin activity in the experimental animals when compared with control. CONCLUSION: Elevated renal compression alone did not create the pathophysiologic derangements seen in AACS. However, prior data from this laboratory found that renal vein compression alone caused a decreased renal blood flow and glomerular filtration and an increased plasma renin activity, plasma aldosterone, and urinary protein leak. These changes are partially or completely reversed by decreasing renal venous pressure as occurs with abdominal decompression for AACS. These data strengthen the proposal that renal vein compression, and not renal parenchymal compression, is the primary mediator of the renal derangements seen in AACS.

Abdomen↗
PubMed2004

Pathology of lumbar nerve root compression. Part 1: Intraradicular inflammatory changes induced by mechanical compression.

STUDY DESIGN: This study is to investigate the intraradicular inflammation induced by mechanical compression using in vivo model. OBJECTIVES: The relationship between the intraradicular edema and nerve fiber degeneration induced by mechanical compression was determined in the nerve root. SUMMARY OF BACKGROUND DATA: Recently some studies reported that mechanical compression increased microvascular permeability of the endoneurial capillaries and resulted in an intraradicular inflammation. These changes may be an important factor of the pathogenesis of radiculopathy. However, the natural courses of the intraradicular inflammation after mechanical compression are still poorly understood. METHODS: In dogs, laminectomy was performed at L7 and the seventh nerve root was exposed to compression at 7.5 gram force (gf) clipping power. The animals were evaluated at 1 and 3 weeks after clipping. After the appropriate period of nerve root compression, Evans blue albumin (EBA) was injected intravenously. The nerve root sections were divided into two groups. The sections were used to investigate the status of the blood-nerve barrier function under the fluorescence microscope. The other sections were used for light and transmission electron microscopic study. RESULTS: After 1 and 3 weeks, intraradicular edema was observed not only at the site of compression but also in the peripheral zone of a compressed anterior root and in the central zone of a compressed posterior root. The evidence of active Wallerian degeneration was also seen in the area of intraradicular edema. In addition, the nerve roots showing Wallerian degeneration were infiltrated by inflammatory cells, such as macrophages and mast cells. CONCLUSIONS: Inflammatory reaction, such as Wallerian degeneration, breakdown of blood-nerve barrier and appearance of macrophage, may be deeply involved in radiculitis arising from mechanical compression, and these factors seem to be important in the manifestation of radiculopathy.

Animals↗