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At least 577 records · Page 32Linked to original sources

PubMed1998

Manual versus mechanical compression for femoral artery hemostasis after cardiac catheterization.

BACKGROUND: Most cardiac catheterizations are performed via femoral artery access. Reported rates of both peripheral vascular complications and success rates for the use of manual and mechanical compression techniques to achieve femoral artery hemostasis after cardiac catheterization vary. OBJECTIVE: To determine is use of a mechanical clamp is as effective as standard manual pressure for femoral artery hemostasis after cardiac catheterization. METHODS: Subjects consisted of 720 patients from 2 community hospitals who had elective diagnostic cardiac catheterization via the femoral artery. The control group (n=343) received manual compression for hemostasis; the study group (n=377) received mechanical compression. Standard protocols were used for the 2 compression techniques. Pressure was applied for a minimum of 10 minutes for 5F and 6F sheaths and catheters and for a minimum of 15 minutes for 7F and 8F sheaths and catheters. Prospective data were collected and analyzed for each patients, including sheath or catheter size, blood pressure, height, weight, age, time from administration of local anesthetic to successful cannulation of the femoral artery, anticoagulation status, total compression time, physician performing the catheterization procedure, nurse or technician who obtained hemostasis, and complications. In follow-up, patients were asked site-specific and functional status questions 1 to 2 days after the catheterization procedure and again 3 days after the catheterization procedure. RESULTS: Data were analyzed by using frequency distributions, measures of central tendency, and measures of variability. Only 1 difference between the 2 groups was significant: manual compression time was 14.93 +/- minutes, whereas mechanical compression time was 17.13 +/- minutes. CONCLUSION: Mechanical compression is as effective as manual compression for femoral artery hemostasis after cardiac catheterization.

Cardiac Catheterization↗

PubMed1986

Epidural cord compression in association with genitourinary neoplasms.

The epidural compression secondary to genitourinary malignancies is relatively uncommon. Of 2118 patients who were diagnosed as having a genitourinary malignancy at the Columbia-Presbyterian Medical Center from 1970-1979, 21 are known to have developed an epidural cord compression by June 30, 1985 (16 from prostate, 1 from urinary bladder, and 4 from renal origin). The following items were reviewed in these 21 patients: age of the patient at diagnosis of the primary tumor; primary site of the genitourinary primary; time in months from the date of diagnosis of the genitourinary primary to the data of diagnosis of the spinal cord compression; methods of diagnosis; presenting symptoms and signs; treatment methods; and survival following the date of diagnosis of the compression. The distribution of location of the epidural metastasis in the current series is as follows: cervical-thoracic, 7%; thoracic, 73%; and lumbosacral, 20%. Skip metastases to the epidural space was the initial sign of malignancy in six patients (31.5%). Five patients (26%) with epidural cord compression survived at least 24 months following the date of diagnosis of their compression. Only two patients in this series with paraplegia (secondary to their compression) had improvement in ambulation following treatment of their compression: of these two patients, one had a prostate primary and the other a renal primary. The indications and techniques for surgery and radiotherapy are briefly described and early diagnosis and treatment are stressed.

Aged↗

PubMed1997

Depth-dependent confined compression modulus of full-thickness bovine articular cartilage.

The objective of this study was to determine the equilibrium confined compression modulus of bovine articular cartilage as it varies with depth from the articular surface. Osteochondral samples were compressed by 8, 16, 24, and 32% of the cartilage thickness and allowed to equilibrate. Intratissue displacement within the cartilage was measured with use of fluorescently labeled chondrocyte nuclei as intrinsic, fiducial markers. Axial strain was then calculated in nine sequential 125 microns thick cartilage layers comprising the superficial 1,125 microns and in a 250 microns thick layer of cartilage adjacent to the cartilage-bone interface. Adjacent osteochondral cores were also tested in confined compression to determine the equilibrium stresses required to achieve the same levels of compression. Stress-strain data for each layer of each sample were fit to a finite deformation stress-strain relation to determine the equilibrium confined compression modulus in each tissue layer. The compressive modulus increased significantly with depth from the articular surface and ranged from 0.079 +/- 0.039 MPa in the superficial layer to 1.14 +/- 0.44 MPa in the ninth layer. The deepest layer 250 microns thick, had a modulus of 2.10 +/- 2.69 MPa. These moduli were markedly different from the apparent "homogeneous" modulus for full-thickness cartilage (0.38 +/- 0.12 MPa) and ranged from 21 to 560% of that value. The relatively low moduli and the compression-induced stiffening of the superficial layers suggest that these layers greatly affect the biomechanical behavior of cartilage, such as during confined compression testing. The delineation of the depth-dependent modulus provides a basis for detailed study of the relationship between the composition, structure, and function of cartilage in such processes as aging, repair, and degeneration.

Animals↗

PubMed2007

Quantitative sensory testing of cold and vibration perception during compression of median nerve at the wrist.

We conducted a sequential study of quantitative sensory testing (QST) during compression-induced conduction block of the median nerve to determine relative vulnerability of the small and large myelinated nerve fibers. We tested cold (CPT) and vibratory perception thresholds (VPT) of the third digit in 15 healthy subjects during constant, localized compression for 30 min of the median nerve at the wrist. The orthodromic sensory nerve action potentials (SNAPs) recorded at wrist and elbow served to monitor the degree of associated conduction block. After the onset of nerve compression, it took 16 min for CPT to show the first change; VPT remained normal for 26 min. CPT recovered 2 min later than VPT after release of compression. The SNAP amplitude at the wrist diminished immediately at the start of compression and declined progressively, whereas the response at the elbow remained the same initially, showing no latency change for 20 min. A nearly identical time course of SNAP changes in the two experiments justified the comparison of separately tested CPT and VPT as a measure of modality-specific vulnerability. Contrary to the common belief, a focal compression sufficient to produce rapidly reversible conduction abnormalities affects the slow-conducting small myelinated fibers mediating cold perception before the fast-conducting large myelinated fibers transmitting vibration perception. The data document the order of modality-specific vulnerability of sensory nerve fibers to mild compression. The finding suggests that testing CPT, rather than VPT, provides a better QST to delineate rapidly reversible symptoms induced by compression.

Action Potentials↗

PubMed1996

Quantitative analysis of the spinal cord motoneuron under chronic compression: an experimental observation in the mouse.

We investigated quantitative changes in spinal cord motoneurons following chronic compression using a mouse model of cervical cord compression. Twenty-five tip-toe-walking Yoshimura (twy) mice with calcified mass lesions compressing the spinal cord posterolaterally at the C1-C2 vertebral levels were compared with five Institute of Cancer Research (ICR) mice that served as controls. Spinal cord motoneurons in the anterior grey horn between the C1 and C3 spinal cord segments were Nissl-stained and counted topographically and then analysed in relation to the extent of spinal cord compression. The number of motoneurons in C1-C3 spinal cord segments decreased significantly with a linear correlation with the transverse area of the spinal cord when the cord was compressed to 50-70% of control values. A significant reduction in the number of motoneurons occurred at the C2-C3 spinal cord segment compressed at the C1-C2 vertebral level. In contrast, at the level rostral to the C1 vertebra, the number of motoneurons increased significantly in proportion to the magnitude of compression. The current study demonstrates that a number of neurons, morphologically consistent with anterior horn cells, were observed at a rostral site absolutely free of external compression where no such cells normally exist.

Animals↗

PubMed1999

Measurement of forces associated with compression therapy.

Compression therapy is the principal treatment for leg ulcers associated with venous disease. The efficacy of compression therapy can be variable, which may in part be owing to the degree of compression applied. However, if the mechanism of action of this treatment could be better understood, it might be possible to improve its efficacy. It is not clear whether assessment of the degree of compression should be made under static or dynamic conditions, or both. A review of methods used previously suggests the need for a new method of assessment allowing continuous monitoring, even during movement. A system for continuous static and dynamic measurements of compression is described. Using an air chamber and manometer to test the system, agreement within +/- 3 mmHg is observed. The system is applied to investigate changes in forces, expressed as pressure, under bandages and compression stockings. Application of five bandage systems by experienced nurses to a volunteer shows a marked variation in applied pressure. During short periods of walking, rapid changes in pressure under compression stockings are observed, including some transients of less than 0.25 s. The method is simple to apply and may help to understand further the mechanism of action of compression therapy.

Bandages↗

PubMed2003

Increased expression of neurotrophins and their receptors in the mechanically compressed spinal cord of the spinal hyperostotic mouse (twy/twy).

The purpose of the present study was to identify any compensatory changes at the site of chronic compression of the spinal cord and neighboring segments. For this purpose, serial immunohistochemical and immunoblot analyses were performed for the expression levels of endogenous brain-derived neurotrophic factor (BDNF), neurotrophin (NT)-3, and their receptors, trkB and trkC in 24 tip-toe walking Yoshimura mice (twy/twy) aged 12-24 weeks. The twy mouse exhibits spontaneous calcified deposits posteriorly at the C1-C2 level, compressing the spinal cord. Immunoreactivities for BDNF, NT-3, trkB and trkC were preferentially localized in the gray matter, particularly in the anterior horn cells. In 24-week-old twy mice with severe compression, expression levels of these neurotrophins at the site of maximal compression were significantly lower than at the less- or non-compressed sites. In contrast, the expression levels of BDNF, NT-3, trkB and trkC were significantly higher at the rostral and caudal sites immediately adjacent to the maximal compression site. No such changes were noted in 12-week-old twy mice or in control Institute of Cancer Research mice. Our results suggest that overexpression of BDNF, NT-3, trkB and trkC in motoneuron areas neighboring the site of mechanical compression may represent compensatory changes in response to the compromised neuronal function at the level of compression, and that these proteins possibly contribute to neuronal survival and plasticity.

Age Factors↗

PubMed2004

The effect of meniscus compression on the biomechanical properties of repaired meniscal lesions. Winner of the AGA-DonJoy Award 2003.

INTRODUCTION: The objective of the present study was to investigate the influence of meniscus compression, as it occurs with weight-bearing, on the biomechanical behavior of different repair types. MATERIALS AND METHODS: Young human meniscal tissue specimens were fitted with a single Bionx Arrow, a Innovasive Meniscal Screw, or a vertical suture (Ethibond 2-0) according to standard clinical practice. Test specimens then underwent repetitive loading with 10 N under 1 N pretension up to a maximum of 1182 cycles and were finally loaded to failure. Half of the cases in each group were additionally subjected to synchronized intermittent compression during the test. The main variables investigated were the number of cycles survived and ultimate failure load. To reduce the complexity, investigations were limited to the peripheral repair site. RESULTS: The number of cycles survived was significantly affected by compression and the type of repair. Arrows and Screws survived 311 and 52 cycles, respectively, without compression, while 983 and 1182 cycles were survived with added compression. In the suture group, no premature failure occurred either with or without compression. Both compression and the type of repair had a significant effect on the ultimate failure load. It increased about twofold in the Arrow and Screw group, while the suture group was not affected. CONCLUSIONS: Compression of the meniscus can substantially increase the pullout resistance of meniscal repair implants and thus seems not to be a factor negatively influencing the stability of the repair.

Adult↗

PubMed2002

Clinical features of the localized girdle sensation of mid-trunk (false localizing sign) appeared in cervical compressive myelopathy patients.

Cervical compressive myelopathy patients sometimes show localized girdle sensation in the mid trunk (so-called false localizing sign). This symptom often confuses physicians, but the clinical features and mechanism of this symptom are still unclear. We investigated the clinical features and possible mechanism. In each of five cases of cervical compressive myelopathy disease with and without mid-truncal girdle sensation, the clinical features, degree and shape of cord compression were analysed. The girdle sensation was expressed as a vague or burning sensation, and was localized with a width of 3 or 4 dermatomes from the T3 to T11 level. There was no correlation between the appearance of the girdle sensation and etiology and level of cervical cord compression. Pyramidal tract signs and disturbance of superficial sensation were observed in all cases. Furthermore, on axial MRI, the midline ventral surface of the cervical cord was remarkably compressed in cases with girdle sensation, as if the compressive lesion entered the anterior medial fissure of the cervical cord. From these findings, this false localizing sign may be caused by severe compression of midline ventral structure of the cervical cord. Ischemia of the thoracic watershed zone of the anterior spinal artery from the compression of the anterior spinal artery at the cervical level might also be considered to be a possible cause.

Adult↗

PubMed1998

Prediction of vertebral artery compression in patients with hemifacial spasm using oblique sagittal MR imaging.

To discriminate between the various compressing vessels of the facial nerves in patients with hemifacial spasm, pre-operative oblique sagittal gradient-echo MR imaging was performed. Forty-two patients underwent pre-operative MR imaging and microvascular decompression. The MR images were divided according to findings into three groups as follows: Group A, a thick and/or long high-intensity line along the root exit zone (REZ) of the facial nerve; Group B, a thin and/or short high-intensity line along the REZ; and Group C, an unreliable image around the REZ. Fifteen images were classified as Group A, 19 as Group B, and 8 as Group C. In Group A, vertebral artery (VA) compression was confirmed intra-operatively in 12 cases and posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA) compression in 3. In Group B, PICA or AICA compression was confirmed intra-operatively in all cases. In Group C, PICA or AICA compression was confirmed intra-operatively in 7 cases and no compression in one. In all cases of VA compression of the facial nerve, the oblique sagittal gradient-echo images demonstrated a thick and/or long high intensity line along the REZ. Oblique sagittal gradient-echo MR imaging is a useful preoperative planning aid, which can predict the possibility of VA compression prior to microvascular decompression for hemifacial spasm.

Facial Nerve↗

PubMed1991

Effects of compression and devascularisation on ulnar nerve function. A quantitative study of regional blood flow and nerve conduction in monkeys.

This study investigated the effects of compression, devascularisation and ischaemia with compression on blood flow and function of the ulnar nerve in monkeys. The hydrogen washout technique assessed blood flow; nerve conduction tests determined nerve function. 100 g of external compression produced a significant but incomplete reduction of intraneural blood flow, when conduction velocity decreased significantly and response amplitude deteriorated to zero 28 minutes after the onset of compression. Short-segment devascularisation stopped blood flow but did not influence response latency or velocity. Amplitude was diminished significantly 44 minutes after devascularisation. Tourniquet ischaemia followed by compression produced temporary variability in latency and velocity, while amplitude was diminished only during the compression phase following ischaemia. The overall results suggested that compression and ischaemia influence the nerve conduction response differently and that the effects of compression are potentiated by previous ischaemia, even if this was of short duration.

Animals↗

PubMed1977

Mechanosensitivity of dorsal root ganglia and chronically injured axons: a physiological basis for the radicular pain of nerve root compression.

The radicular pain of sciatica was ascribed by Mixter and Barr to compression of the spinal root by a herniated intervertebral disc. It was assumed that root compression produced prolonged firing in the injured sensory fibers and led to pain perceived in the peripheral distribution of those fibers. This concept has been challenged on the basis that acute peripheral nerve compression neuropathies are usually painless. Furthermore, animal experiments have rarely shown more than several seconds of repetitive firing in acutely compressed nerves or nerve roots. It has been suggested that "radicular pain" is actually pain referred to the extremity through activation of deep spinal and paraspinal nociceptors. Our experiments on cat lumbar dorsal roots and rabbit sural nerves have confirmed that acute compression of the root or nerve does not produce more than several seconds of repetitive firing. However, long periods of repetitive firing (5-25 min) follow minimal acute compression of the normal dorsal root ganglion. Chronic injury of dorsal roots or sural nerve produces a marked increase in mechanical sensitivity; several minutes of repetitive firing may follow acute compression of such chronically injured sites. Such prolonged responses could be evoked repeatedly in a population of both rapidly and slowly conducting fibers. Since mechanical compression of either the dorsal root ganglion or of chronically injured roots can induce prolonged repetitive firing in sensory axons, we conclude that radicular pain is due to activity in the fibers appropriate to the area of perceived pain.

Action Potentials↗

PubMed2005

A comparative study between axial compression and lateral fall configuration tested in a rat proximal femur model.

BACKGROUND: Conventional testing method for evaluation of rat hip failure force is based on an axial compression approach. However, as the most osteoporotic hip fractures are a result of a lateral fall, it is necessary to establish mechanical testing methods more close to clinical conditions. This study was therefore designed to evaluate the differences in hip mechanical failure force to be tested between 'axial compression' and 'lateral fall configuration' in a rat proximal femur model. METHODS: Eighteen 10-month-old female Wistar rats were body-weight matched and divided into ovariectomized group (n = 9) and sham group (n = 9). All rats were euthanized 3 months after surgery. The bilateral proximal femora of each rat were excised. The left femur served for testing to failure in a fall configuration fashion while the right femur was tested using axial compression approach. After mechanical testing, the anterior-posterior radiographs were taken to identify the fracture mode and measure the Pauwel's angle between the fracture line and the line perpendicular to the femoral shaft long axis. FINDINGS: The failure force in fall configuration was significantly correlated with but lower than that tested in axial compression. A comparison between the ovariectomized and sham group showed that the failure force in both fall configuration and axial compression was found significantly higher in the sham group than that in the ovariectomized group. However, the logistic regression analysis revealed that the fall configuration approach had larger discrimination power. Radiographs showed that almost all samples fractured at the base of the femur neck. The Pauwel's angle in fall configuration group was significantly larger than that in axial compression group. INTERPRETATION: In comparison with the characteristics of axial compression test, the fall configuration approach generated higher shearing stress with larger bending moment to the bone and induced susceptibility to fracture at lower mechanical load. Although the failure force obtained from the two testing configurations revealed significant correlation, the mechanical testing in fall configuration demonstrated higher sensitivity in identifying the estrogen-deficiency induced deterioration of hip mechanical failure force as compared with that in axial compression. These findings suggested the potential application of lateral fall configuration in evaluation of improvement effects of intervention stratagems on hip mechanical failure force involving an ovariectomized rat model.

Accidental Falls↗

PubMed2006

The Gurnham equation in characterizing the compressibility of pharmaceutical materials.

Limitations of the Heckel equation in characterizing material compression behavior have been well reported. In this work, the Gurnham equation, which was first introduced in chemical engineering, is proposed as an alternate method of evaluating the compressibility of pharmaceutical powders. The Gurnham equation was adapted for tablet compression and the estimated slope parameter c was proposed to represent material compressibility. Data from the compression of four commonly used excipients (microcrystalline cellulose, corn starch, lactose monohydrate, and dibasic calcium phosphate dihydrate) and one drug (acetaminophen) were evaluated using the Gurnham equation. Using compression data at different peak pressures, linear relationships between porosity and lnPressure of the five materials were obtained. The determined parameter c expresses the compressibility of materials. The analysis of previous experimental data, including granulations, mixtures and co-processed materials also indicates that c might be a representative parameter for material compressibility.

Acetaminophen↗

PubMed2006

Analysis of large compression loads on lumbar spine in flexion and in torsion using a novel wrapping element.

Axial compression on the spine could reach large values especially in lifting tasks which also involve large rotations. Experimental and numerical investigations on the spinal multi motion segments in presence of physiological compression loads cannot adequately be carried out due to the structural instability and artefact loads. To circumvent these problems, a novel wrapping cable element is used in a nonlinear finite element model of the lumbosacral spine (L1-S1) to investigate the role of moderate to large compression loads on the lumbar stiffness in flexion and axial moments/rotations. The compression loads up to 2,700 N was applied with no instability or artefact loads. The lumbar stiffness substantially increased under compression force, flexion moment, and axial torque when applied alone. The presence of compression preloads significantly stiffened the load-displacement response under flexion and axial moments/rotations. This stiffening effect was much more pronounced under larger preloads and smaller moments/rotations. Compression preloads also increased intradiscal pressure, facet contact forces, and maximum disc fibre strain at different levels. Forces in posterior ligaments were, however, diminished with compression preload. The significant increase in spinal stiffness, hence, should be considered in biomechanical studies for accurate investigation of the load partitioning, system stability, and fixation systems/disc prostheses.

Compressive Strength↗

PubMed1997

Optic nerve contact and compression by the carotid artery in asymptomatic patients.

PURPOSE: To estimate the frequency and clinical correlates of contact and compression of the intracranial optic nerve by the supraclinoid carotid artery in asymptomatic patients. METHODS: In a retrospective study, we identified asymptomatic patients who had undergone magnetic resonance imaging with sequences that could be used to evaluate the relation between the intracranial optic nerve and the carotid artery. These patients underwent neuroimaging evaluations for reasons unrelated to loss of vision, optic neuropathy, or carotid artery disorders. The relation between the optic nerve and carotid artery was graded in a standardized manner. The effect of a number of clinical covariates on the risk of compression was evaluated using multiple logistic regression. RESULTS: The frequencies of some of the artery-nerve relationships included contact of one or both optic nerves in 70 (70%) of 100 patients; bilateral compression in 12 (12%) of 100 patients; and unilateral compression with no arterial contact or compression on the opposite side in five (5%) of 100 patients. The estimated odds of compression were significantly increased as the diameter of the carotid artery increased. CONCLUSIONS: Among asymptomatic patients, supraclinoid carotid artery contact with the intracranial optic nerve occurs frequently. Anatomic compression, on the other hand, especially when unilateral, occurs infrequently. The risk of anatomic compression of the optic nerve is directly proportional to the diameter of the carotid artery.

Adolescent↗

PubMed2003

Temporal regulation of chondrocyte metabolism in agarose constructs subjected to dynamic compression.

The temporal response of chondrocyte metabolism in agarose constructs subjected to different dynamic compression regimes was investigated. The current study explored the effects of continuous or intermittent compression using various duty cycles of dynamic compressive loading, over a 48 h culture period. For the continuous compression experiments, duty cycles ranged from 5400 to 172,800 and intermittent compression delivered a total of 86,400 cycles. Large numbers of duty cycles significantly stimulated proteoglycan synthesis with maximal levels obtained for constructs subjected to 12h of intermittent compression. The shortest duration of intermittent compression suggested that further cycles are inhibitory for cell proliferation. Nitrite release was independent of the length or type of compressive regime applied. The uncoupled nature of the metabolic response determined in this study suggests that mechanical conditioning regimes may be fine tuned to selectively stimulate key metabolic parameters of relevance to cartilage tissue engineering.

Animals↗

PubMed1993

Spinal cord compression secondary to prostate carcinoma: treatment and prognosis.

Of 35 patients with prostate carcinoma and suspected spinal cord compression 26 (74%) had myelograms and/or magnetic resonance imaging studies demonstrating epidural spinal cord compression. In 5 of 26 patients (19%) spinal cord compression was the first indication of prostate cancer. All patients were initially treated with radiation, steroids and androgen deprivation therapy. Three patients underwent laminectomy. Of 12 patients (100%) ambulatory at presentation 12 remained ambulatory. Of 12 patients (83%) who were paraparetic at presentation 10 were ambulatory after treatment. However, 2 of these patients subsequently had recurrent compression and became paraplegic. Overall, 7 of 26 patients (27%) had recurrent compression. Of 5 patients who either presented with paraplegia or in whom paraplegia developed secondary to recurrent spinal cord compression 4 remained paraplegic despite treatment. The average survival of these 5 patients after treatment was 3.9 months versus 18 months for the group as a whole. In ambulatory or paraparetic patients radiation, androgen deprivation therapy and steroids are effective palliative therapy. However, patients who present with paraplegia or in whom paraplegia developed secondary to recurrent compression are often not palliated by this combination therapy. Prophylactic radiation of vertebral metastases discovered concurrently with compressive metastases may be valuable in preventing paraplegia.

Aged↗