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PubMed1995

Relationship between viscosity and determined injection pressure in angiography catheters for common roentgen contrast media.

The viscosity of 8 commercially available contrast media (CM) at 2 or 3 concentrations were measured as a function of concentration and temperature, using a rotational viscosmeter. Further on, by use of an automated injector, injection pressures were measured for 3 of the CM at various concentrations, temperatures, catheter lengths, catheter diameters and flow rates. The experiments were performed as fractional factorial designs. The correlation between the injection pressure and the viscosity was found to be log-linear, and an empiric equation was established for this relationship. The relative reduction of viscosity - and therby injection pressure - with increasing injection temperature, was largest for the most concentrated CM. Iodixanol and iotrolan, the 2 nonionic dimers investigated, demonstrated an increased viscosity compared to the nonionic monomers at equal concentrations. However, all CM investigated could be used with an acceptable injection pressure either by relatively small changes in catheter conditions or by adjustment of injection temperature closer to body temperature.

Angiography↗
PubMed2000

The influence of "sputum-like gel" viscosity on crackle characteristics in a mechanically ventilated porcine lung model.

This study investigated the influence of airway secretion viscosity on the characteristics of crackle sounds produced using a mechanically ventilated porcine lung model. Aqueous ultrasonic methylene blue stained gel solutions of viscosity 100, 150 and 200 P were prepared and instilled into 15 isolated, mechanically ventilated, porcine lungs immersed in water. Sound signals recorded by a hydrophone before and after instillation of gel were subjected to both fast Fourier transform and wave-form analysis. At the completion of sound recording, the main bronchi were dissected and the location of the stained gel was photographically recorded. Wave-form analysis demonstrated that expiratory phase crackle incidence and amplitude were both significantly higher than inspiratory phase data. This study demonstrates that crackle duration and amplitude are inversely related to gel viscosity and that electronic lung sound analysis can provide indirect evidence of sputum viscosity.

Animals↗
PubMed2003

Transgenic mice overexpressing erythropoietin adapt to excessive erythrocytosis by regulating blood viscosity.

Severe elevation of red blood cell number is often associated with hypertension and thromboembolism resulting in severe cardiovascular complications. However, some individuals such as high altitude dwellers cope well with an increased hematocrit level. We analyzed adaptive mechanisms to excessive erythrocytosis in our transgenic (tg) mice that, due to hypoxia-independent erythropoietin (Epo) overexpression, reached hematocrit values of 0.8 to 0.9 without alteration of blood pressure, heart rate, or cardiac output. Extramedullar erythropoiesis occurred in the tg spleen, leading to splenomegaly. Upon splenectomy, hematocrit values in tg mice decreased from 0.89 to 0.62. Tg mice showed doubled reticulocyte counts and an increased mean corpuscular volume. In tg mice, plasma volume was not elevated whereas blood volume was up to 25% of the body weight compared with 8% in wild-type (wt) siblings. Although plasma viscosity did not differ between tg and wt mice, tg whole-blood viscosity increased to a lower degree (4-fold) than expected from corresponding hemoconcentrated wt blood (8-fold). This moderate increase in viscosity is explicable by the up to 3-fold higher elongation of tg erythrocytes at physiologic shear rates. Apart from the nitric oxide-mediated vasodilation we reported earlier, adaptation to high hematocrit levels in tg mice involves regulated elevation of blood viscosity by increasing erythrocyte flexibility.

Adaptation, Physiological↗
PubMed2006

The pendulum test as a tool to evaluate passive knee stiffness and viscosity of patients with rheumatoid arthritis.

BACKGROUND: The pendulum test of Wartenberg is a technique commonly used to measure passive knee motion with the aim to assess spasticity. We used this test to evaluate changes of the knee angular displacement, passive stiffness and viscosity in rheumatoid arthritis patients. Stiffness and viscosity represent passive resistances to joint motion associated with the structural properties of the joint tissue and of the muscular-tendon complex. Stiffness can be considered an intrinsic property of the tissues to resist deformation, while viscosity is related to cohesive forces between adjacent layers of tissues. Both parameters may influence the joint range of motion affecting angular displacement. METHODS: Nine women with rheumatoid arthritis were compared with a group of healthy women. With the subject half-lying, the relaxed knee was dropped from near-full extension and the characteristics of the ensuring damped unsustained knee oscillation evaluated. The kinematics of leg oscillations was recorded using ultrasonic markers (Zebris CMS HS 10) and the kinetic data were calculated from kinematic and anthropometric measures. RESULTS: Knee stiffness significantly increased (p < 0.001) in patients with respect to the control group, while differences in viscosity were not significant. Moreover, the amplitudes of first knee flexion (the maximal flexion excursion after knee release) and first knee extension (the maximal extension excursion after the first knee flexion) were significantly decreased (p < 0.001). A regression analysis showed that disease severity correlated moderately with stiffness (R2 = 0.68) and first flexion (R2 = 0.78). Using a multivariate regression, we found that increasing stiffness was the main factor for the reduction of flexion and extension motions. CONCLUSION: We showed that the Wartenberg test can be considered a practical tool to measure mechanical changes of knee caused by rheumatoid arthritis. This novel application of Wartenberg test could be useful to follow up the effects of pharmacological and rehabilitative interventions in this disease.

Adult↗
PubMed1975

Effects of viscosity and ATP concentration on the movement of reactivated sea-urchin sperm flagella.

Spermatozoa from the sea urchin, Lytechinus pictus, can be demembranated with solutions containing Triton X-100 and 5mM-CaCl2 and reactivated in ATP solutions containing low concentrations (10(-9)M) Of free Ca2+ ion to give symmetrical bending wave movements, even at very low ATP concentrations. At ATP concentrations of 0.01-0.02 mM the reactivated spermatozoa have beat frequencies near 1 Hz, nearly normal bend angles, and wave-lengths about 50% longer than normal. 2. The effects of increased viscosity, obtained by addition of methyl cellulose to the reactivation solutions, on bend angle and beat frequency decrease with decreasing ATP concentration, and become almost undetectable at 0.01 mM ATP. On the other hand, the effect of increased viscosity on wavelength shows relatively little change with ATP concentration, although it is noticeably reduced at 0.01 mM ATP. 3. These observations suggest that the beat frequency at low ATP concentrations is determined by an intrinsic rate-limiting process, in contrast to the viscocity-limited behaviour at high beat frequencies. Quantitative agreement with the experimental results is obtained with a model in which ATP concentration and viscosity each determine the rates of one step in a two-step reaction cycle which determines the beat frequency. 4. Two other models which can qualitatively explain the effects of ATP concentration and viscosity on flagellar beat frequency fail to show quantitative agreement with the experimental results. In one of these models, ATP concentration determines the maximum rate of shear between filaments. In the other, ATP concentration determines a time delay which is required to bring the active moment into phase with the elastic moments which would be expected to dominate the bending resistance at low beat frequencies.

Adenosine Triphosphate↗
PubMed1999

Comparison of flow in numerical and physical models of a ventricular assist device using low- and high-viscosity fluids.

The flows in a model of a ventricular assist device (VAD) were investigated numerically and experimentally for two different Newtonian test fluids. These were a blood analogue fluid and a much higher viscosity fluid. A finite volume method was employed to solve the governing equations for a three-dimensional unsteady laminar flow on a transient grid. The numerical solutions were compared with experimental results from an identical physical model. The experimental flows were investigated by flow visualization and by laser Doppler velocity measurements at selected points in the flow field. The validation was based on comparisons of flow patterns and of non-component velocity-time histories. The maximum Reynolds numbers in the inflow tube of the model VAD were approximately 460 and 3300 using the high- and low-viscosity fluids respectively. The investigation showed that the flow patterns were better predicted for the high-viscosity fluid. However, the agreement between the velocity-time histories was found to be slightly better for the low-viscosity fluid. The discrepancies in the flow patterns may be due to intermittent turbulence with a further contribution from numerical diffusion.

Blood Flow Velocity↗
PubMed2004

Changes in blood viscosity with heavy and light exercise.

To clarify the relationship of the intensity of acute exercise to sudden cardiac death, we examined the effects of short-term heavy and light exercise on whole blood viscosity. Nine healthy sedentary male volunteers performed ten minutes of heavy (more than 95% of maximum oxygen consumption) or light (60% to 65% of maximum oxygen consumption) exercise. Blood samples were obtained before, immediately after, and one hour after exercise. The whole blood viscosity was immediately examined with an oscillation-type viscometer and was found to increase significantly after exercise and subsequently return to baseline levels within one hour after exercise. The whole blood viscosity increased by a similar degree after heavy or light exercise. Therefore, our results suggest that there is a similar risk of sudden cardiac death, due to increased whole blood viscosity, after short-term heavy or light exercise.

Adult↗
PubMed2004

Inhibitory effects of psyllium on rat mineral absorption were abolished by reduction of viscosity with partial hydrolysis.

Psyllium husk, a highly viscous fiber, has beneficial effects for health, but has been reported to inhibit absorption of calcium. The present study found the effects of fiber viscosity on calcium, magnesium, and zinc absorption with partially degraded psyllium preparations to be one fifth viscosity (LD-HP) and one seventieth viscosity (HD-HP) using normal and ovariectomized rats. Magnesium absorption was reduced with ingestion of intact psyllium (50 g/kg diet) for 4 weeks but this reduced absorption was increased with lower viscous psyllium preparations. Moreover, the absorption in the HD-HP group was higher than in the control group (100 g cellulose/kg diet) in ovariectomized rats. Changes in calcium and zinc absorption were similar to those in magnesium absorption. Cecal pH was reduced only in rats fed HD-HP in both normal and ovariectomized rats. These results indicate that reduction of psyllium viscosity tends to counter inhibitory effects on mineral absorption.

Animals↗
PubMed1992

Plasma viscosity and C-reactive protein after total hip and knee arthroplasty.

We studied the changes in plasma viscosity and C-reactive protein to establish normal values after total hip or knee arthroplasty. Viscosity decreased from 1.68 (+/- 0.017) to 1.57 (+/- 0.014) on the first postoperative day and thereafter rose to 1.60 (+/- 0.019), 1.75 (+/- 0.015), and 1.74 (+/- 0.011) on the third, seventh and fourteenth days respectively. Six to eight weeks after operation it had returned to pre-operative levels. A viscosity above the upper limit of the laboratory range, obtained more than two months after operation, may be considered as abnormal. The C-reactive protein level increased significantly on the first postoperative day and then decreased from a peak on the second day, attaining nearly normal levels at six to eight weeks after operation. It may be a more sensitive indicator of deep postoperative infection than plasma viscosity.

Adult↗
PubMed2006

Clinical laboratory measurement of serum, plasma, and blood viscosity.

This article discusses the fundamentals for measuring the viscosity of whole blood, serum, and plasma and its application to the diagnosis of hyperviscosity syndrome. We describe some of the terminology in the field, including relevant definitions, the different units of measure, and general principles of clinical laboratory viscosity measurement. The 3 main categories of instrumentation for viscosity measurement--capillary, falling-sphere, and rotational viscometers--are discussed. We compare the various types of instrumentation for their usefulness with various types of clinical specimens. Relevant features that may be important in selecting a viscometer are described. We describe our 1.5-year experience with the viscometer that we chose. We hope the information in this review will be useful to pathologists and clinical laboratory staff in explaining the available choices for measuring serum, plasma, and whole blood viscosity.

Blood Viscosity↗
PubMed1981

Filterability and other methods of approaching red cell deformability. Determinants of blood viscosity and red cell deformability.

The major determinants of blood viscosity are RBC concentration, plasma viscosity, RBC aggregation and RBC deformation. RBC deformation is determined by the intrinsic deformability of the cell and the shear stress acting on the cell surface. In using filterability tests to assess RBC deformability, it is necessary to eliminate variations in other determinants of blood viscosity and to specify the rheological conditions of the test. Further theoretical and experimental work is needed for the interpretation of filterability tests in terms of cell geometry, internal viscosity and membrane properties.

Blood↗
PubMed1981

Filterability and vascular disease--I. Red cell filterability in diabetes mellitus: its relation to other methods of measuring deformability and to blood viscosity.

Erythrocyte deformability, blood viscosity and other rheological variables were measured in 30 diabetics and 28 normal control subjects. Measurements of red cell rheology were made simultaneously by filtration of whole blood, centrifugation and viscometry of packed red cells. The diabetics showed a significant reduction of erythrocyte deformability measured by filtration, an increase in flexibility measured by centrifugation and values similar to normals for viscometry of packed red cells. Plasma viscosity but not whole blood viscosity (shear rates 23 and 230 s-1) was increased in the diabetics. Erythrocyte flexibility as measured by centrifugation was significantly related to blood viscosity and plasma fibrinogen and glucose in the diabetics, however, neither filtration nor viscometry of packed red cells correlated with other rheological variables. It seems likely that multiple rheological abnormalities are present in diabetes mellitus. Conclusions about erythrocyte rheology in particular will depend critically on the methodology used.

Adult↗
PubMed1986

Lysolecithin affects the viscosity, permeability, and peptic susceptibility of gastric mucin.

The effect of lysolecithin and lecithin on gastric mucin viscosity, permeability to hydrogen ion, and degradation by pepsin was investigated. Preincubation with lysolecithin produced a marked decrease in the glycoprotein viscosity. This decrease was concentration-dependent and at 10 mM lysolecithin reached a value of 74%. A 25% increase in mucin viscosity was obtained with 10 mM lecithin. Permeability measurements showed that 10 mM lecithin increased the retardation ability of the glycoprotein to hydrogen ion by 11%, whereas a 12% decrease in the retardation capacity of the glycoprotein was obtained with 10 mM lysolecithin. The results of peptic activity assay indicated that whereas lecithin had no effect on the rate of mucin proteolysis, the lysolecithin exerted significant (75%) stimulatory effect. The results suggest that lysolecithin in the stomach weakens the integrity of the protective mucus layer by promoting peptic degradation, reducing the ability to resist acid penetration, and decreasing viscosity of its mucin component.

Animals↗
PubMed1999

Color Doppler and hormone replacement therapy: the role of thromboxane and plasma viscosity.

The aim of the study was to evaluate the plasma thromboxane and plasma viscosity in relation with Doppler flow parameters in postmenopausal patients treated with hormone replacement therapy. Thirty-two postmenopausal (follicle-stimulating hormone > 40 IU/l and estradiol < 100 pmol/l) women (mean age +/- SD, 54.7 +/- 2.9 years) participated in the study and were submitted to continuous estradiol transdermal supplementation and 12-day courses of medroxyprogesterone acetate every second month. Doppler resistances at the level of the uterine and internal carotid arteries, thromboxane plasma levels and plasma viscosity were analyzed in basal condition and after 1, 3 and 6 months. During hormone supplementation, the pulsatility index significantly decreased at the level of the analyzed arteries. Similarly, plasma thromboxane levels and plasma viscosity were significantly reduced. Significant correlations were found between thromboxane plasma concentrations, plasma viscosity and uterine artery resistances. Thus hormone replacement therapy seems to be responsible for both direct and indirect modifications at the level of the vessel wall physiology.

Blood Viscosity↗
PubMed1997

Viscosity measurements for LEH suspended in different plasma expanders.

To investigate the possibility of hemodilution with oxygen carrying fluid, we measured the viscosity effects of LEH which was suspended in different weight percentage of plasma expanders for different shear rates. All of LEH/Plasma expander suspensions show shear thinning flow behavior, and the viscosity of those suspensions increase with increased the weight percentage of each expander in suspensions for a fixed shear rate. Compared the viscosity data to those of human blood at 40% of hematocrit, LEH/albumin suspensions contained with 4% to 8% of albumin are the most suitable, whereas LEH/dextran (Dex) suspensions contained with 6% Dex70c is the least favorable suspension media for LEH. In point of viscosity effects, hemodilution with LEH/albumin or LEH/0.9% oxypolygelatin (Gel) may be valuable for further testing their efficacy in animal model.

Animals↗
PubMed1999

PE-PEG/LEH can reduce its interactions with plasma expanders indexed through viscosity measurements.

To investigate whether PE-PEG coated LEH (PE-PEG/LEH) can reduce its interaction with different plasma expanders and possibly suspended in those expanders, we measured the viscosity of PE-PEG/LEH suspended in different plasma expanders as an index for the interactions. The results showed that lower viscosity values for PE-PEG/LEH were observed compared with LEH especially in low shear rate regions (e.g., 7.72 +/- 1.46 cp vs. 14.91 +/- 1.03 cp for gamma = 2.25 sec-1, respectively). Moreover, the viscosity values for PE-PEG/LEH suspended in fibrinogen suspensions were much less than those of LEH in the same media at low shear rate regions (e.g., 7.72 +/- 1.59 cp vs. 25.78 +/- 1.59 cp, gamma = 2.25 sec-1, respectively). Similar results were observed for PE-PEG/LEH suspended in 1.83% of oxypolygelatin (Gel) suspensions and 1.5% hydrooxyethyl starch (HES) compared to LEH in the same suspension media. On contrast, PE-PEG/LEH suspended in dextran (Dex) showed that dramatically increasing the viscosity values in low shear rates compared with LEH suspended in the same media (e.g., 78.87 +/- 0.56 cp vs. 51.08 +/- 3.52 cp, gamma = 2.25 sec-1, respectively) were observed. Since only minor interactions with Gel, HES or fibrinogen suspensions were observed, we suggest that PE-PEG/LEH suspended in those media but not in Dex can possibly serve for resuscitation oxygen-carrying fluids.

Animals↗
PubMed1987

Low- versus high-viscosity bone cement. Fixation of hip prostheses analyzed by roentgen stereophotogrammetry.

Sixteen patients were examined by roentgen stereophotogrammetry during the first year after total hip arthroplasty. Eight prostheses were fixed with low-viscosity and eight with high-viscosity cement. Eight acetabular components, four in each group, migrated cranially, and three femoral components, all in the low-viscosity group, migrated distally. Our findings suggest that low-viscosity cement does not improve prosthetic fixation.

Bone Cements↗
PubMed1990

Early detection of prosthetic-hip loosening. Comparison of low- and high-viscosity bone cement.

In 1987, we reported the 1-year migration of the prosthetic components in 16 hips followed by roentgen stereophotogrammetry after fixation with either low- or high-viscosity cement. We now report the migration of these prosthetic components during another 2 postoperative years. Eight acetabular components, four in each group, migrated cranially; and four femoral components, three in the low-viscosity and one in the high-viscosity group, migrated distally. All but two migrations were obvious 4 months postoperatively, which indicates that what is called late loosening is the result of late detection rather than of late occurrence of loosening. Low-viscosity cement did not provide improved prosthetic fixation.

Bone Cements↗