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PubMed1985

[Postoperative deep venous thrombosis prevention with intermittent sequential compression].

The euglobulin lysis time (ELT) in antecubital vein and femoral vein was investigated in 35 patients before and after bilateral intermittent sequential leg compression for one hour. After compression, ELT in antecubital vein was shortened, and that in femoral vein was significantly shortened (p less than 0.05). beta-thromboglobulin, fibrinopeptide B beta 15-42 and alpha 2-plasmin inhibitor were also investigated, but no significant change was found after compression. The mean and peak blood velocity of the femoral vein before and during compression was measured using Doppler ultrasound in 20 patients. The mean blood velocity increased about 183% (p less than 0.001), and the peak blood velocity also increased 178% (p less than 0.001). ELT was measured pre- and post-operatively in 31 patients who had intermittent sequential compression during operation and succeeding two days and in 31 controls which had no compression. Both in antecubiltal vein and in femoral vein, ELT in the compression group was significantly shorter than that of control group in the first postoperative day. This study demonstrates that intermittent sequential compression of the legs increased fibrinolytic activity, and this effect may contribute to the prevention of deep venous thrombosis.

Adult↗

PubMed1988

Transformation of the female breast during compression at mammography with special reference to the importance for localization of a lesion.

The effects of compression during mammography were studied in 187 breasts. The aims of this study were to investigate: 1) How the skin moves, 2) how the gland tissue is transformed, 3) if there is a relationship between outer and inner alterations and 4) the practical implications for aspiration biopsy. In this study, several experiments were carried out to investigate the effects of compression during clinical mammography in adult female breasts. The transformation of the breast during compression was investigated by means of external skin markings and internal markings using the biopsy needle and the hookwire at preoperative localization. The extent of the mammary gland was measured in the different standard projections during mammography. The calculation of the depth of a lesion during cranio-caudal compression was performed on the latero-medial radiographs. The result was checked with water-soluble radiographic contrast medium. The mean value of differences between observed and calculated depth was 3.7 mm. 1. The breast transforms during compression. 2. The biopsy needle in the breast and the barium markings on the skin incline ventrally in 96 per cent during latero-medial compression. The preoperative hookwire inclines ventrally in 92 per cent. 3. The extension of the gland parenchyma (the longest diagonal) is almost equal in all standard projections, including the medio-lateral oblique one. 4. The skin in the inframammary sulcus is firmly attached to the thoracic wall. This form of fixation determines principally the movements of the breast and limits the transformation during compression. 5. The movements of the skin are connected to the movements of the dense tissue, gland parenchyma. There is a connection between the ventral and descending inclination. These inclinations are caused by the same transformation of the breast. 6. Due to the regular movements of the breast during different compression directions, it is possible to predict the location of a lesion in three dimensions from standard mammograms.

Adult↗

PubMed1987

Multichannel compression processing for profound deafness.

Three-channel amplitude compression followed by frequency shaping was used to process test sentences for five profoundly deaf subjects, and the recognition scores were compared to scores achieved with frequency shaping only. At preferred levels, the scores of three of the five subjects showed a statistically significant but not dramatic advantage for compression; the averages of the scores for these three subjects were 29.2 percent for the uncompressed speech and 39.5 percent for the compressed speech. The preferred-level scores of the other two subjects did not show a statistically significant advantage for compression; averages were 33.7 percent for uncompressed speech and 36.1 percent for compressed speech. Tests at input levels 10 dB and 15 dB below preferred levels were also given to four of the subjects (the fifth had to leave the experiment early). In the reduced-level tests all four subjects showed a statistically significant advantage for compression. The averages of reduced-level uncompressed scores for the four subjects were 10.7 percent and 15.2 percent at -15 dB and -10 dB levels, compared to compressed scores at these levels of 31.7 percent and 32.5 percent. When visual cues were added to the auditory presentation in an exploratory experiment with one subject, the benefit of compression carried over into the higher scores.

Acoustics↗

PubMed1986

Multichannel syllabic compression for severely impaired listeners.

Two listeners with congenital hearing losses characterized by flat audiograms and dynamic ranges of 18-33 dB were tested with three compression systems and one (reference) linear amplification system. The compression systems placed progressively larger amounts of speech energy within the listener's residual dynamic range, by raising to audibility and compressing 25, 50, and 90 percent of the short-term input amplitude distribution in each of 16 frequency bands. The comparison linear system was defined by adjusting six octave-wide bands of speech to comfortable levels. System performance was evaluated with nonsence CVC syllables presented at a constant input level and spoken by two talkers. Extensive training was provided to ensure stable performance. The results were notably speaker-dependent, with compression consistently providing better performance for one speaker, linear amplification for the other. Averaged over speakers, however, there was no net advantage for any of the compression systems for any listener. The use of high compression ratios and large input ranges tended to degrade perception of initial consonants and vowels. Under some conditions, however, final consonant scores were higher with compression than with linear amplification. Compression generally enhanced the distinction between stops and fricatives, but degraded spectral-concentration and relative-intensity cues required to identify place of articulation.

Adult↗

PubMed1977

8. Self-compressing implants in the management of fractures.

Internal fixation of fractures has become increasingly important since the introduction of self-compressing implants. Rigidity of fixation thus ensured permits primary bone healing. Two types of self-compressing implants are available--screws and plates. The former produces compression between fracture fragments, the latter, along the long axis of the bone. Two common types of plates are the dynamic compression plate and the Osteo self-compressing plate. Use of self-compressing implants requires familiarity with the technique, a definite plan of operation, and strict asepsis and lack of infection in the patient. Indications for the technique include failure or unsuitability of closed reduction of fractures, care of associated serious soft-tissue injuries, and displaced intra-articular fractures. Use of self-compressing plates hastens rehabilitation, lessens joint stiffness and reduces the duration of hospitalization. The incidence of nonunion with self-compression techniques is lower than with traditional methods of fracture management.

Bone Plates↗

PubMed1981

Effect of intermittent pneumatic and graduated static compression on factor VIII and the fibrinolytic system.

Intermittent pneumatic compression (IPC) or graduated static compression stockings, both effective mechanical methods in the prophylaxis of postoperative deep venous thrombosis, have been investigated in 50 patients regarding the effect of compression on the fibrinolytic system and factor VIII activators. All the patients were subjected to one of the two methods before operation upon varicose veins. In 38 patients IPC with a pressure of 40 mmHg was applied on one leg or arm for at least two hours. In 23 of these patients the compression pattern was slow, two minutes' inflation and two minutes' deflation period. In the remaining 15 patients the compression pattern was quick, three seconds' inflation, followed by 20 seconds' deflation, three cycles a minute. Twelve patients were treated with a compression stocking on one leg for about 24 hours before the operation. Blood samples for determination of fibrinolytic activity and factor VIII in plasma were obtained before and immediately after the end of compression and application of a stocking, respectively. Also the level of plasminogen activator activity (PA) in the vein wall was determined. Neither IPC nor the application of an elastic stocking had any demonstrable effect on the variables studied. In addition, the results did not vary with the rate (slow or quick) or with the duration of IPC, sex or site of application (arm or leg) of IPC. Blood samples from the compressed leg were also uninfluenced.

Adult↗

PubMed1980

[Studies on the dynamic durability of dental restorative materials. (Part 2) Properties for the repeated impact compressive load ot composite resins (author's transl)].

Based on the fracture energy form the compression test of composite resins under the repeated impact loads in compression after stored for a period in water at 37 degrees C, the dynamic durability of commercially used composite resins was evaluated. The results obtained were summarized as follows. (1) The fracture energy of composite resins under the repeated impact compressive loads after stored in water at 37 degrees C is clearly lower than the initial fracture energy. Particularly the decrement of the initial fracture energy for Concise, Epolite 100 and Superlux after stored for 30 days in water at 37 degrees C is influenced considerably both by the physicochemical degradation caused by water and the mechanical deterioration caused by the repeated impact compressive loads, but Clearfil is superior to the mechanical deterioration. (2) In each composite resins, there is a close correlation between fracture energy and compressive strain. In composite resins without Superlux, also a correlation is in fracture energy and compressive strength. (3) In clearfil, concise and Epolite 100, the morphology of fracture in compression test of composite resins which are subjected to and are subjected to the repeated impact loads in compression is classified in a mode of shear fracture, but in Superlux, a mode of crack fracture.

Composite Resins↗

PubMed1994

Duplex-guided compression of iatrogenic femoral artery pseudoaneurysms.

The purpose of this report is to review our experience with duplex-guided compression in the management of iatrogenic femoral artery pseudoaneurysms. From February 1991 to July 1992, 13 consecutive asymptomatic femoral artery pseudoaneurysms were managed initially with duplex-guided compression. Twelve of these complications followed interventional cardiac procedures; the remaining case followed lysis of a femoral to tibial bypass. A Quantum Angiodynograph I duplex imager with a 5-MHz probe was used during this study. After the origin of the pseudoaneurysm was identified, compression was applied with the transducer head to obliterate flow in the pseudoaneurysm, while maintaining flow in the parent artery. Successful thrombosis was accomplished in 12 patients. The mean interval between the original femoral puncture and duplex-guided compression was 9.0 days (range, 1-22 days). The mean compression time was 30 minutes (range, 15-45 minutes). Pseudoaneurysm size ranged from 1.0 to 5.0 cm. Follow-up imaging, performed within 72 hours after compression, demonstrated sustained pseudoaneurysm thrombosis and patent femoral artery segments. Four patients were managed as out-patients, without the need for anesthesia or sedation. Eight patients were managed in the hospital, seven following interventional cardiac procedures, and one following bypass revision. Duplex-guided compression failed in one case. This patient was successfully treated operatively, at which time repair of both the profunda and superficial femoral artery was required. Asymptomatic iatrogenic femoral artery pseudoaneurysms can be successfully managed with duplex-guided compression. This maneuver appears to be a simple and cost-effective approach for initial management of these lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1993

Hemodynamic alterations in venous blood flow produced by external pneumatic compression.

Venous stasis associated with prolonged bed rest can enhance the risk of deep venous thrombosis (DVT). Pneumatic compression of the lower extremities can reduce this risk by preventing venous stasis. When selecting a method of leg compression for their patients, physicians must chose between two distinctly different types of compression devices. One device applies pressure with a single-chambered sleeve to the below knee region while the other applies pressure in a sequential gradient fashion from the ankle to the thigh. The current prospective study was designed to evaluated the ability of two such devices to increase blood flow in the profunda femoral vein. Venous blood flow velocity, compression time, and vein diameter were measured in nine normal experimental subjects using an Accuson duplex-Doppler before, during and after leg compression. Compression with the single-chambered device produced a significant rise in venous blood flow velocity; however, this could not be maintained and our results indicate a higher average velocity was achieved with the sequential gradient device. The sequential gradient device also moved a greater volume of blood and achieved a higher average blood flow rate. The time between deflation of the sleeve and return of a phasic respiratory signal was greater after compression with the sequential gradient device. These results suggest that sequential gradient compression produces the type of hemodynamic alterations needed to reduce the risk of DVT by achieving a sustained increase in venous blood flow and more completely emptying of the veins in the leg.

Analysis of Variance↗

PubMed1993

A device for measuring compression force in mammography.

Compression in mammography is an accepted technique for improving image quality and reducing dose, but excessive compression can cause pain and other undesirable effects. Therefore, maximum compression force should be measured in a quality assurance programme. A compression force meter, based on a load cell design, has been constructed and used to make compression force measurements on three GE Senographe 600T mammography machines. These measurements show that the conversion from pneumatic pressure (as indicated on the machine) to applied compression force is given by Compression Force (N) = (79.0 +/- 0.9) x Pneumatic Pressure (bars) + (12.2 +/- 4.0). Using this equation and pneumatic pressure settings on nine GE Senographe 600T units in our quality assurance programme, the maximum compression force in clinical use ranges from 102 to 150 N with a mean of 126 N. This is lower than guidelines used in the United States and the United Kingdom.

Female↗

PubMed2000

Tenascin-C in tendon regions subjected to compression.

Tendon regions subjected almost exclusively to tension differ from regions subjected to high levels of compression as well as tension. Regions not exposed to compression consist primarily of spindle-shaped fibroblasts surrounded by densely packed longitudinally oriented collagen fibrils formed principally from type-I collagen. In contrast, regions subjected to compression have a fibrocartilagenous structure and composition: they consist of spherical cells surrounded by a matrix containing hyaline cartilage proteoglycans (aggrecan) and type-II collagen as well as type-I collagen. Reducing their adhesion to the matrix may help cells in the latter regions establish and maintain a spherical shape and minimize their deformation when the tissue is subjected to mechanical stress. We hypothesized that expression of tenascin-C, an anti-adhesive protein, is part of the adaptation of tendon cells to compression that helps establish and maintain fibrocartilagenous regions. To test this hypothesis, we compared segments of bovine flexor tendons subjected to repetitive compression (distal) with segments that are not subjected to compression (proximal) to determine whether they differed in tenascin-C content and expression. RNA and protein analyses showed that tenascin-C expression was elevated in the distal tendon. Tendon cells from the distal segment expressed more tenascin-C mRNA than did cells from the proximal segments for as long as 4 days in cell culture, indicating that increased tenascin-C expression is a relatively stable feature of the distal cells. Moreover, purified tenascin-C inhibited the attachment of cultured tendon cells to fibronectin. These observations support the hypothesis that tenascin-C expression is a cellular adaptation to compression that helps establish and maintain fibrocartilagenous regions of tendons by decreasing cell-matrix adhesion.

Animals↗

PubMedDate not supplied

Radiological follow-up of new compression fractures following percutaneous vertebroplasty.

The purpose of the present study was to ascertain chronological changes in the analgesic effects of percutaneous vertebroplasty (PVP) on osteoporotic vertebral compression fractures and to radiologically follow new compression fractures after PVP. Seventy-six patients (206 vertebral bodies) were followed radiologically for a mean of 11.5 months. A visual analog scale (VAS; 0-10) was used to assess pain severity, and frontal and lateral plain radiographs of the thoracic and lumbar vertebrae were taken 1-3 days and 1, 4, 10, and 22 months after PVP. The average VAS score was 7.2 +/- 2.0 (mean pain score +/- standard deviation) before PVP, 2.5 +/- 2.3 at 1-3 days after PVP, 2.2 +/- 2.3 at 1 month, 1.9 +/- 2.2 at 4 months, 1.8 +/- 2.4 at 10 months, and 1.0 +/- 0.2 at 22 months. A new compression fracture was confirmed in 56 vertebral bodies in 28 patients (36.8%), affecting 38 adjacent vertebral bodies (67.8%), 17 nonadjacent vertebral bodies (30.4%), and 1 treated vertebral body (1.8%). A new compression fracture occurred within 1 week of PVP in 2 vertebral bodies (3.6%), between 1 week and 1 month after PVP in 22 (39.3%), between 1 and 3 months in 12 (21.4%), between 3 and 6 months in 12 (21.4%), and after more than 6 months in 8 (14.3%). PVP was highly effective in relieving the pain associated with osteoporosis-induced vertebral compression fractures, and this analgesia was long lasting. Radiological follow-up observation revealed new compression fractures in about one-third of patients. More than half of these new compression fractures occurred in adjacent vertebral bodies within 3 months of PVP.

Contrast Media↗

PubMed1997

Three-dimensional topographic analysis of spinal accessory motoneurons under chronic mechanical compression: an experimental study in the mouse.

We investigated the effect of chronic mechanical compression of the cervical spinal cord on the number of spinal accessory motoneurons in 25 tiptoe-walking Yoshimura mice. The animals had calcified deposits in the atlantoaxial membrane at the C1-C2 vertebral level, compressing the spinal cord posterolaterally. Motoneurons of the spinal accessory nerve between C1 and C5 segments were labelled using wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injected into the sternocleidomastoid muscles. The counted cells were processed into a three-dimensional computer display to analyse the cytoarchitectonic changes caused by external cord compression. The number of WGA-HRP-labelled spinal accessory motoneurons was significantly reduced on the affected side. The number of motoneurons in compromised C2 and C3 cord segments correlated linearly with the extent of mechanical compression, but no such relationship was present on the contralateral side. There was an increase in the number of WGA-HRP-labelled spinal accessory motoneurons in the medial cell pools of the anterior grey horn at a level most rostral to the compression, and in the ventrolateral cell pools at levels immediately rostral to the compression. Our findings suggest that the spinal accessory motoneurons translocate rostral to the area of external compression in order to avoid mechanical injury.

Animals↗

PubMed2004

Functional and morphological changes of lumbar nerve roots induced by mechanical compression or the nucleus pulposus in contact with the root: analysis of fiber size-dependent vulnerability in rabbits.

The variation in symptoms of spinal nerve root damage may be caused by the difference of the size of damaged nerve fiber or difference between the mechanical influence and some chemical factors. We studied the relative vulnerability of small versus large myelinated fibers to a focal compression and/or an application of nucleus pulposus. We prepared the mechanical compression model by clipping the nerve root and the nucleus pulposus model by applying autologous nucleus pulposus on the nerve root in a rabbit and evaluated nerve root damage with respect to its fiber diameter. Nerve conduction velocity (NCV) of large myelinated nerve fiber was reduced significantly in every group compared with a sham operation group (sham) after 1 day in compression, but in the nucleus pulposus group (NP) the velocity was reduced significantly compared with sham only after 7 days. Histologic examination revealed that the number of damaged large fibers increased significantly in the compression group compared with sham after 3 days, but there was no difference in NP. NCV of small myelinated nerve fibers was reduced significantly in both the compression and NP groups compared with sham after 7 days. Histologic study showed the number of damaged small fibers increased significantly in the compression group compared with sham after 7 days. However, in the NP group the number of damaged fibers did not increase compared with sham. In conclusion, large myelinated nerve fiber was damaged earlier than small myelinated nerve fiber by compression, while nerve fiber damage caused by only the nucleus pulposus had no relation to nerve fiber size.

Action Potentials↗

PubMed2006

Context based error modeling for lossless compression of EEG signals using neural networks.

Two-stage lossless data compression methods involving predictors and encoders are well known. This paper discusses the application of context based error modeling techniques for neural network predictors used for the compression of EEG signals. Error modeling improves the performance of a compression algorithm by removing the statistical redundancy that exists among the error signals after the prediction stage. In this paper experiments are carried out by using human EEG signals recorded under various physiological conditions to evaluate the effect of context based error modeling in the EEG compression. It is found that the compression efficiency of the neural network based predictive techniques is significantly improved by using the error modeling schemes. It is shown that the bits per sample required for EEG compression with error modeling and entropy coding lie in the range of 2.92 to 6.62 which indicates a saving of 0.3 to 0.7 bits compared to the compression scheme without error modeling.

Data Compression↗

PubMed1984

Changes in fast axonal transport during experimental nerve compression at low pressures.

The minimal pressure for impairment of fast anterograde axonal transport was determined in rabbit vagus nerve. Proteins, transported by fast anterograde axonal transport, were labeled by a microinjection of [3H]leucine into the nodose ganglion, and a small compression chamber was applied around the cervical vagus nerve. In this way the nerve was subjected to acute, graded compression. Compression at 20 mm Hg for 2 h as well as sham compression did not induce accumulation of axonally transported proteins at the level of compression. However, a pressure of 30 mm Hg for 2 h induced a block of axonal transport at the site of compression. The causes of the axonal transport block are discussed as well as the minimal pressure level in relation to pressures found in clinical nerve compression lesions.

Animals↗

PubMed1993

Malignant epidural spinal cord compression associated with a paravertebral mass: its radiotherapeutic outcome on radiosensitivity.

PURPOSE: To evaluate clinical characteristics and functional outcome of malignant epidural spinal cord compression associated with a paravertebral mass. METHODS AND MATERIALS: Between 1987 and 1990, 136 patients with epidural spinal cord compression were treated with irradiation. Of these, 25 patients (18%) had epidural spinal cord compression associated with a paravertebral mass. This report is based on analysis of these 25 patients. Fourteen patients received 3000 cGy in 10 fractions. Seven received 4000 cGy in 16 fractions. Four received 2000 cGy in 5 fractions. Motor function was evaluated by five grades. RESULTS: Lung cancer accounted for the majority of epidural spinal cord compression with a paravertebral mass (60%) followed by lymphoma (8%) and kidney tumor (8%). This pattern of epidural spinal cord compression has a longer duration of pain before developing neurologic symptoms and has a high propensity of the upper thoracic spine involvement by an apical lung cancers. The functional outcome of radiation treatment reveals a significant difference between moderately radiosensitive tumors (lung, prostate, cervix, esophagus) and very radiosensitive tumor (lymphoma). None of the nonambulatory patients became ambulatory following radiotherapy except for the very radiosensitive tumors. Higher doses of radiation treatment (4000 cGy in 16 fractions) did not improve functional outcome. CONCLUSION: Due to the larger tumor burden, radiation treatment for epidural spinal cord compression associated with a paravertebral mass is not as effective as treatment of epidural spinal cord compression without a paravertebral mass except for the very radiosensitive tumor. Therefore, combined treatment modality might be beneficial for improving functional outcome.

Female↗

PubMed2005

Detection of unsuspected spinal cord compression in melanoma patients by 18F-fluorodeoxyglucose-positron emission tomography.

AIM: Positron emission tomography (PET) using (18)F-fluorodeoxyglucose can detect early or small metastatic deposits of melanoma and guide subsequent correlative anatomical imaging and treatment. The aim of this study was to assess the value of PET in demonstrating spinal cord compression by otherwise unsuspected metastatic disease. METHODS: Reports of 1365 PET studies performed on patients with melanoma were reviewed. Fifty patients considered to be at risk of spinal cord compression on the basis of PET were identified and 35 patients were analysed. Magnetic resonance imaging and computed tomography were used to confirm or refute the diagnosis. The symptoms and signs at the time of PET and follow-up status were compared between patients with and without confirmed spinal cord compression. RESULTS: In nine patients (26%) compression of the spinal cord or adjacent neurological structures was confirmed and eight of these patients had immediate treatment. Survival was poor in both patient groups, but three patients with confirmed compression maintained good neurological functional status following treatment. CONCLUSION: PET can detect imminent, unsuspected spinal cord compression in patients with metastatic melanoma. Immediate anatomical imaging of the spine is recommended in patients who have evidence of spinal cord compression on PET.

Adult↗