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PubMed1996

Ultrasound-guided compression closure of postcatheterization pseudoaneurysms during concurrent anticoagulation: a review of seventy-seven patients.

PURPOSE: Data from our institution and elsewhere have demonstrated that ultrasound-guided compression closure (UGCC) is an effective method of treating postcatheterization pseudoaneurysms. Whereas patients receiving anticoagulation do not have as high a success rate as those not receiving anticoagulants, there have been no large series evaluating the factors associated with success or failure in patients receiving anticoagulation. The purpose of this study is to determine whether uninterrupted anticoagulation interferes with successful UGCC of pseudoaneurysms and to identify factors associated with success or failure. METHODS: From May 1991 to September 1994, 238 cases of attempted UGCC of pseudoaneurysms were performed in our vascular laboratory. Only patients who received uninterrupted heparin, warfarin, or both at the time of pseudoaneurysm compression were eligible for inclusion into the study. Seventy-seven patients were identified who met the study criteria. RESULTS: Successful pseudoaneurysm compression was obtained in 56 (73%) patients, whereas 21 (27%) patients had a failed UGCC. In the successfully treated group, seven (12.5%) required between two to three compression attempts to induce sustained thrombosis. There was no statistical difference in age, sex, sheath size, days after procedure, location of pseudoaneurysm, or number of chambers in the pseudoaneurysm between those patients who had a successful repair and those who did not. If the pseudoaneurysm was less than 4 cm in diameter, 51 of 65 patients (78%) had a successful repair compared with 5 of 12 patients (42%) with a pseudoaneurysm of 4 cm or greater (p = 0.013). There was no statistical difference between success and failure in patients receiving warfarin alone (3.73 mean international normalized ratio, 72% success rate), heparin alone (mean activated partial thromboplastin time of 63 seconds, 92% success rate), or heparin and warfarin (mean activated partial thromboplastin time of 70 seconds, mean international normalized ratio of 4, success rate of 67%). No arterial or venous thrombosis occurred during pseudoaneurysm compression. CONCLUSION: Successful UGCC of pseudoaneurysms occurred in a large percentage of patients receiving full-dose, uninterrupted anticoagulation. The only factor influencing success was the size of the pseudoaneurysm.

Adult↗
PubMed1990

Outcome analysis of patients with normal compression US examinations.

Prior studies have documented the accuracy of compression ultrasound (US) for use in evaluating patients with clinically suspected deep venous thrombosis (DVT) of the lower extremity. A normal compression US examination is considered indicative of no thrombotic disease, and anticoagulant therapy is withheld. There are no long-term data supporting treatment decisions based solely on normal compression US results. The authors undertook a long-term (8-33-month) review of 1,111 normal compression US examinations performed on 1,022 patients. Outcome analysis obtained through review of imaging records, inpatient charts, and death certificates failed to document sequelae of untreated DVT in all but five patients with negative examinations. Three patients again presented with clinical symptoms of DVT that were subsequently documented with compression US, and two patients reportedly died of pulmonary embolism with no documentation of DVT several months after the initial negative study. Because of the clinical acceptance of this test and the subsequent increased demand for its use, compression US has quadrupled the yearly detection rate of DVT at the authors' institution. With the results of prior controlled studies and this favorable outcome analysis study, compression US is recommended as the diagnostic modality of choice for suspected DVT.

Adolescent↗
PubMed1988

Shape of forced expiratory flow-volume curves in infants.

An inflatable cuff was used to generate partial forced expiratory flow-volume (FEFV) curves in 36 infants with and without obstructive airway disease. Curves were recorded in each infant over a range of compression pressures as high as and exceeding the pressure required for the maximal partial FEFV curve. The maximal curves were quantitated and compared with passive compliance and conductance of the respiratory system and absolute lung volume measured by whole-body plethysmography. In some infants, the transmission of pressure between cuff and pleural space was determined. Partial FEFV curve shapes generated with a standardized compression pressure calculated from the transmission of pressure data to give an increase in pleural pressure at FRC of 10 cm H2O were compared between infants. For these standardized compressions, infants with convex curves tended to have better respiratory function than did those with concave curves. The combination of a concave curve and flow limitation during tidal expiration was associated with the worst function. Two parameters, the ratio of forced maximal expiratory flow (measured from the maximal partial FEFV curve) to tidal expiratory flow (measured from the expiratory flow-volume curve of tidal breathing) at midtidal volume (Vm1d(forced/tidal] and the minimal compression pressure required to generate maximal expiratory flow at FRC (Pmin), satisfactorily quantified respiratory function without the need for size correction with absolute lung volume. In addition, Vm1d(forced/tidal) provides an index of expiratory flow reserve. We conclude that useful information can be provided from the shape of a partial FEFV curve in an infant, provided that curves are generated by a standardized compression pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchiolitis↗
PubMed2006

Effect of humidity on lung surfactant films subjected to dynamic compression/expansion cycles.

The surface activity of bovine lipid extracted surfactant (BLES) preparations used in surfactant replacement therapy is studied in dynamic film compression/expansion cycles as a function of relative humidity, surfactant concentration, compression rate, and compression periodicity. BLES droplets were formed in a constrained sessile droplet configuration (CSD). Images obtained during cycling were analyzed using axisymmetric drop shape analysis (ADSA) to yield surface tension, surface area, and drop volume data. The experiments were conducted in a chamber that allowed both humid (100% RH), and "dry" air (i.e. less than 20% RH) environments. It was observed that in humid environments BLES films are not stable and tend to have poor surface activity compared to BLES films exposed to dry air. Further analysis of the data reveal that if BLES films are compressed fast enough (i.e. at physiological conditions) to avoid film hydration, lower minimum surface tensions are achieved. A film hydration-relaxation mechanism is proposed to explain these observations.

Animals↗
PubMed2003

[Indications for the surgical treatment of the funnel chest].

AIM OF THE STUDY: to establish the indications for surgical treatment of the funnel chest. PATIENTS AND METHODS: There was a retrospective and prospective analysis performed of the methods of investigation and treatment of 504 patients operated for the funnel chest during the period of 35 years (1968-2002). In order to make a right diagnosis and to establish the indications for surgical treatment a standard algorithm of investigations was prepared: examination, collecting the detailed life history, establishing a type and a degree of deformation, chest and column radiological examination, ECG, spirography and heart ultrasound examination. RESULTS: On basis of physical examination and anamnestic data the most clinical signs and complaints were established. The heart compression was found in preoperative X-rays in 476 (94.4%) patients, the heart was rotated and dislocated in 441 (87.5%) patients. Postoperatively 96.1% of patients were free of the heart compression symptoms and for 71.8% the heart rotation has disappeared. The pathological ECG findings were recorded for 382 (71.8%) patients and abnormal spirograms were taken for 31 (8.5%) patients. CONCLUSIONS: The following indications for the funnel chest surgical treatment were established: - obvious funnel chest diagnozed by physical examination, - complaints and disturbances clear from anamnestic data, - heart rotation and compression established by radiological examination, - pathological findings in cardiorespiratory system (ECG, echocardiography, and spirography). An optimal age for operation was found out to be between 3 and 7 years.

Age Factors↗
PubMed2005

Axonal and extracellular matrix responses to experimental chronic nerve entrapment.

We have analyzed the ultrastructural and histopathological changes that occur during experimental chronic nerve entrapment, as well as the immunohistochemical expression of chondroitin sulfate proteoglycan (CSPG). Adult hamsters (n = 30) were anesthetized and received a cuff around the right sciatic nerve. Animals survived for varying times (5 to 15 weeks) being thereafter perfused transcardially with fixative solutions either for immunohistochemical or electron microscopic procedures. Experimental nerves were dissected based upon the site of compression (proximal, entrapment and distal). CSPG overexpression was detected in the compressed nerve segment and associated with an increase in perineurial and endoneurial cells. Ultrastructural changes and data from semithin sections were analyzed both in control and compressed nerves. We have observed endoneurial edema, perineurial and endoneurial thickening, and whorled cell-sparse pathological structures (Renaut bodies) in the compressed nerves. Morphometrical analyses of myelinated axons at the compression sites revealed: (a) a reduction both in axon sectional area (up to 30%) and in myelin sectional area (up to 80%); (b) an increase in number of small axons (up to 60%) comparatively to the control group. Distal segment of compressed nerves presented: (a) a reduction in axon sectional area (up to 60%) and in myelin sectional area (up to 90%); (b) a decrease in axon number (up to 40%) comparatively to the control data. In conclusion, we have shown that nerve entrapment is associated with a local intraneural increase in CSPG expression, segmental demyelination, perineurial and endoneurial fibrosis, and other histopathological findings.

Animals↗
PubMed2000

Long-range density fluctuations in orthoterphenyl as studied by means of ultrasmall-angle x-ray scattering.

The structure factor of a fragile glass-forming liquid orthoterphenyl was measured in the previously inaccessible intermediate q range between the conventional light scattering (LS) and small-angle x-ray scattering (SAXS) q ranges using the low-angle scattering beam line at the European Synchrotron Radiation Facility. At low q the structure factor exhibits an excess scattering and matches well the LS data. This excess scattering is due to long-range density fluctuations also observed in the isotropic component of scattered light. At high q the structure factor decays to a plateau corresponding to the isothermal compressibility in agreement with the conventional SAXS data. In the intermediate q range, the structure factor exhibits a power law q dependence which indicates that the excess scattering is due to fractal aggregates of denser domains.

Journal Article↗
PubMed1999

Mean-shape vector quantizer for ECG signal compression.

A direct waveform mean-shape vector quantization (MSVQ) is proposed here as an alternative for electrocardiographic (ECG) signal compression. In this method, the mean values for short ECG signal segments are quantized as scalars and compression of the single-lead ECG by average beat substraction and residual differencing their waveshapes coded through a vector quantizer. An entropy encoder is applied to both, mean and vector codes, to further increase compression without degrading the quality of the reconstructed signals. In this paper, the fundamentals of MSVQ are discussed, along with various parameters specifications such as duration of signal segments, the wordlength of the mean-value quantization and the size of the vector codebook. The method is assessed through percent-residual-difference measures on reconstructed signals, whereas its computational complexity is analyzed considering its real-time implementation. As a result, MSVQ has been found to be an efficient compression method, leading to high compression ratios (CR's) while maintaining a low level of waveform distortion and, consequently, preserving the main clinically interesting features of the ECG signals. CR's in excess of 39 have been achieved, yielding low data rates of about 140 bps. This compression factor makes this technique especially attractive in the area of ambulatory monitoring.

Electrocardiography↗
PubMed2001

[Lumbar nerve root compression--results of the quality assurance study 1993-1998].

Summary. This multicenter quality assurance study investigated 14 334 cases with lumbar nerv root compression between 1993 and 1998. Patient data, diagnostics, therapy and course as well as neurological status pre- and posttreatment have been investigated for each year. There was an obvious growing number of patients between 60 and 79 years of age, who have been operated. The rate raised from 20% to 28%. Age, comorbiditiy and complication rate as well as length of stay showed a positive correlation. Outpatient CTscan lost diagnostic importance (82% --> 65%) compared to MRI (16% --> 41%). Myelography regained interest in only conservatively treated patients due to difficult indication assessment (40% --> 64%). The rate of intraoperative antibiotics rose from 42% to 59% without change of infection rate. Intra- and postoperative complication rates came down from 5.6% to 2.1% and 6.9% to 1.8% respectively. Pre- and postoperative neurological findings remained unchanged.

Aged↗
PubMed2006

System for deep venous thrombosis detection using objective compression measures.

A system for objective vessel compression assessment for deep venous thrombosis characterization using ultrasound image data and a sensorized ultrasound probe is presented. Two new objective measures calculated from applied force and transverse vessel area are also presented and used to describe vessel compressibility. A modified star-Kalman algorithm is used for feature detection in acquired ultrasound images, and objective measures of vessel compressibility are calculated from the detected features and acquired force and location data from the sensorized probe. A three-dimensional shape model of the examined vessel that includes compressibility measures mapped as colors to its surface is presented on the user interface, as well as a virtual representation of the image plane. The compressibility measures were validated using expert segmentation of healthy and diseased vessels and compared using paired t-tests, which showed a significant difference between healthy and diseased cases for both measures. 100% sensitivity and specificity were obtained for both measures. The system was implemented in real-time (16 Hz) and evaluated using a tissue phantom and on healthy human subjects. Sensitivity was 100% and 60%, while specificity was 97% for both measures when implemented. The initial results for the system and its components are promising.

Algorithms↗
PubMed2005

Enhancing the rate of the Diels-Alder reaction using CO2 + ethanol and CO2 + n-hexane mixed solvents of different phase regions.

The reaction rate of the Diels-Alder reaction between N-ethylmaleimide and 9-hydroxymethylanthrance in CO2 + ethanol and CO2 + hexane mixed solvents of different compositions were determined by in situ UV/vis spectroscopy at 318.15 K and different pressures. The density of the mixed solvents at different pressures was also determined and the isothermal compressibility was calculated using the density data. The activation volume of the reaction was calculated based on the dependence of rate constant (kc) on pressure. It was demonstrated that the kc was very sensitive to the pressure in the mixed solvents near the critical region and the kc increased dramatically as pressure approached dew points, critical point, and bubble points of the mixed solvents. However, the kc in the mixed solvents outside the critical region or in pure CO2 was not sensitive to pressure. At suitable conditions, kc could be 40 times larger than that in acetonitrile. The activation volume of the reaction was nearly independent of pressure as the pressure was much higher than the phase separation pressure of the mixed solvents, while it increased considerably as pressure approached the bubble points, critical point, and dew points from high pressure. The clustering of the solvent molecules with the reactants and the activated complex in the reaction systems near the phase boundary in the critical region may be the main reason for the interesting phenomena observed. This work also shows that, using pure CO2 as the solvent, the reaction cannot be carried out in the critical region of the solvent due to the limitations of the reactants, while it can be conducted in the critical region of mixed solvents of suitable compositions, where the solvents are highly compressible and the reaction rate can be tuned effectively by pressure.

Anthracenes↗
PubMed2005

Nanomechanics of opposing glycosaminoglycan macromolecules.

In this study, the net intermolecular interaction force between a chondroitin sulfate glycosaminoglycan (GAG)-functionalized probe tip and an opposing GAG-functionalized planar substrate was measured as a function of probe tip-substrate separation distance in aqueous electrolyte solutions using the technique of high resolution force spectroscopy. A range of GAG grafting densities as near as possible to native cartilage was used. A long-range repulsive force between GAGs on the probe tip and substrate was observed, which increased nonlinearly with decreasing separation distance between probe tip and substrate. Data obtained in 0.1 M NaCl was well predicted by a recently developed Poisson-Boltzmann-based theoretical model that describes normal electrostatic double layer interaction forces between two opposing surfaces of end-grafted, cylindrical rods of constant volume charge density and finite length, which interdigitate upon compression. Based on these results, the nanomechanical data and interdigitated rod model were used together to estimate the electrostatic component of the equilibrium modulus of cartilage tissue, which was then compared to that of normal adult human ankle cartilage measured in uniaxial confined compression.

Biomechanical Phenomena↗
PubMed2006

Group delay of acoustic emissions in the ear.

It is commonly accepted that the cochlea emits sound by a backward traveling wave along the cochlear partition. This belief is mainly based on an observation that the group delay of the otoacoustic emission measured in the ear canal is twice as long as the forward delay. In this study, the otoacoustic emission was measured in the gerbil under anesthesia not only in the ear canal but also at the stapes, eliminating measurement errors arising from unknown external- and middle-ear delays. The emission group delay measured at the stapes was compared with the group delay of basilar membrane vibration at the putative emission-generation site, the forward delay. The results show that the total intracochlear delay of the emission is equal to or smaller than the forward delay. For emissions with an f2/f1 ratio <1.2, the data indicate that the reverse propagation of the emission from its generation site to the stapes is much faster than a forward traveling wave to the f2 location. In addition, that the round-trip delays are smaller than the forward delay implies a basal shift of the emission generation site, likely explained by the basal shift of primary-tone response peaks with increasing intensity. However, for emissions with an f1 << f2, the data cannot distinguish backward traveling waves from compression waves because of a very small f1 delay at the f2 site.

Algorithms↗
PubMed2002

Thoracolumbar spine mechanics contrasted under compression and shear loading.

The mechanical properties of the human spine have been studied extensively in compression, but there remains a lack of fundamental data in shear. The overall goal of this study was to contrast the mechanics of the thoracolumbar functional spinal unit (FSU) under compression and shear-type loads by evaluating endplate deformation, disc pressures, and kinematics between the different loading types. Eleven T12-L1 and one L1-L2 human FSUs were tested. Compression loads consisted of pure compression, extension-compression, flexion-compression, lateral left and right compression applied individually to a maximum of 500 N. Shear loading consisted of posterior, anterior, left, and right shear to a maximum of 500 N. Intervertebral motions, disc pressure, and vertebral body deformations were recorded for all loads. The deformations were measured using strain gauge rosettes at three points on the inferior vertebral body and one on the superior endplate of the inferior vertebra. The disc pressures and endplate deformations measured were significantly less in shear loading compared to compression and did not change significantly with the type of compression load. Vertebral rim strains were generally greater under shear loading compared with compression. The mechanics of load transfer in compression was the production of high disc pressures which were not linearly correlated with the central endplate deformation. In shear, the mechanism appears to be via the annulus fibrosus without the development of significant disc pressure. These differences between compression and shear loading may have implications for injury mechanisms in the thoracolumbar spine.

Adult↗
PubMed2003

Cauda equina compression after trauma: an unusual presentation of spinal epidural lipoma.

STUDY DESIGN: A case report is presented. OBJECTIVE: To describe a case of a spinal epidural lipoma presenting as a cauda equina compression syndrome secondary to trauma. SUMMARY OF BACKGROUND DATA: Epidural lipomas are rare lesions that present as back pain with progressive neurologic symptoms. METHODS: A patient presenting with cauda equina compression after an injury was investigated and treated surgically. The clinical follow-up period was 3 years. RESULTS: Imaging of the lumbar spine showed an extradural mass compressing the cauda equina. The patient underwent emergency surgery, and an adipose mass was removed. Neurologic recovery was observed and maintained 3 years after surgery. CONCLUSIONS: Previously asymptomatic epidural masses such as lipomas can present with neurologic deficit after trauma. Appropriate imaging can help in the diagnosis and management of such cases.

Aged↗
PubMed2006

[Metastatic spinal cord compression syndrome. A retrospective analysis of 297 patients].

INTRODUCTION: The purpose of this study was to look at the prognostic factors and the effects (regression of symptoms and survival rate) of the treatment given to patients with metastatic spinal cord compression syndrome (MSCCS). MATERIALS AND METHODS: Data from 297 patients who were treated at Odense University Hospital from 1989 to 2003 were collected through a retrospective evaluation of medical records. RESULTS: The patients' median age was 67 years. The most common primary diagnoses were prostate cancer, breast cancer and lung cancer. The patients' motor function at the time of diagnosis, the primary cancer diagnosis, the time from primary diagnosis to development of MSCCS and the treatment given were all significant prognostic factors. The patients receiving surgery (whether or not also receiving radiotherapy) had a significantly higher survival rate (4.8 months) than those who received only radiotherapy (3.3 months). CONCLUSION: Primary diagnosis, the degree of symptoms and the time from primary diagnosis to development of MSCCS are important prognostic factors that should be considered when choosing the treatment for a given patient. With an active attitude, it is possible to retain walking skills during the remaining and often short lifetime. Patients whose general condition allows for it should receive acute surgery followed by radiotherapy.

Aged↗
PubMed2001

Dynamic compression inhibits the synthesis of nitric oxide and PGE(2) by IL-1beta-stimulated chondrocytes cultured in agarose constructs.

Both mechanical loading and interleukin-1beta (IL-1beta) are known to regulate metabolic processes in articular cartilage through pathways mediated by nitric oxide ((*)NO) and PGE(2). This study uses a well-characterized model system involving isolated chondrocytes cultured in agarose constructs to test the hypothesis that dynamic compression alters the synthesis of (*)NO and PGE(2) by IL-1beta-stimulated articular chondrocytes. The data presented demonstrate for the first time that dynamic compression counteracts the effects of IL-1beta on articular chondrocytes by suppressing both (*)NO and PGE(2) synthesis. Inhibitor experiments indicated that the dynamic compression-induced inhibition of PGE(2) synthesis and stimulation of proteoglycan synthesis were (*)NO mediated, while compression-induced stimulation of cell proliferation was (*)NO independent. The inhibition of (*)NO and PGE(2) by dynamic compression is a finding of major significance that could contribute to the development of novel strategies for the treatment of cartilage-degenerative disorders.

Animals↗
PubMed2004

Presymptomatic spondylotic cervical cord compression.

STUDY DESIGN: We conducted a cohort study of clinically asymptomatic spondylotic cervical cord compression cases with the primary end point of the development of clinical signs of cervical myelopathy. OBJECTIVES: To investigate whether various demographic, clinical, radiologic, and electrophysiological parameters could predict progression from clinically asymptomatic (preclinical) spondylotic cervical cord compression to symptomatic myelopathy. SUMMARY OF BACKGROUND DATA: The data available on the prediction of the outcome in surgical and conservative treatment of spondylotic cervical myelopathy are controversial. Little is known about the clinical natural history of asymptomatic magnetic resonance image-detected spondylotic cervical cord compression and/or changes of signal intensity. METHODS: A group of 66 patients (32 women, 34 men, median age 50 years) with magnetic resonance signs of spondylotic cervical cord compression but without clear clinical signs of myelopathy was followed prospectively for at least 2 years (range, 2-8 years; median, 4 years). Various demographic, clinical, imaging, and electrophysiological parameters were correlated with clinical outcome. RESULTS: Clinical signs of myelopathy during the follow-up period were detected in 13 patients (19.7%). The only variables significantly associated with the development of clinically symptomatic spondylotic cervical myelopathy (SCM) were the presence of symptomatic cervical radiculopathy, electromyographic signs of anterior horn lesion, and abnormal somatosensory-evoked potentials. A multivariate logistic regression model based on these variables correctly classified 90% of cases into 2 subgroups: a group with development of symptomatic SCM and that without clinical manifestation of subclinical cervical cord compression. CONCLUSIONS: Electrophysiological abnormalities together with clinical signs of cervical radiculopathy could predict clinical manifestation of preclinical spondylotic cervical cord compression.

Adult↗