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PubMed1989

Is increased plasma viscosity a risk factor for high blood pressure?

Data from several epidemiologic studies have suggested that, among other variables, hematocrit and fibrinogen may constitute risk factors for high blood pressure. As part of a population survey for cardiovascular risk factors, plasma viscosity and hemoglobin were measured. Blood pressure was determined under standardized conditions according to the recommendations of the AHA. A two-stage age-sex-stratified cluster sample of 5,312 persons, aged twenty-five to sixty-four years, was selected from a mixed urban/rural target population of 282,279 (total population approximately 533,000). A net response of 79.3% was achieved. Multiple logistic regression analyses including plasma viscosity, hemoglobin, body mass index, alcohol consumption, smoking behavior, and total serum cholesterol as independent variables were run controlling for both age and sex. Plasma viscosity appeared as a significant main effect in all analyses and demonstrated the strongest association with high blood pressure next to body mass index. Whether this association implies a causal relationship cannot be answered from cross-sectional data. However, even if plasma hyperviscosity represents a secondary phenomenon in hypertension, it might be of prognostic relevance. There is evidence that increased plasma viscosity may contribute to myocardial hypertrophy. Therefore hypertensives with impaired blood fluidity might constitute a subgroup at particular risk for cardiovascular complications. When antihypertensive drugs are selected, their influence on blood viscosity should be taken into account.

Adult↗
PubMed2007

Subglottic secretion viscosity and evacuation efficiency.

Ventilator-associated pneumonia (VAP) is a common nosocomial pneumonia that occurs in critically ill patients and results in mortality rates as high as 71%. Subglottic secretions (SSs) are a known risk factor. Several clinical trials have shown that continuous aspiration of subglottic secretions (CASS) reduces the risk of VAP by nearly half. Optimal suction pressure levels needed to efficiently evacuate viscous SSs are unknown. The purpose of this study was to describe SSs and the effective suction pressure (20 mmHg, 30 mmHg, 40 mmHg, and 50 mmHg) needed to maximize evacuation efficiency based on SS volume (2 ml, 4 ml, and 6 ml) and viscosity (watery, thick, and gel-like). A laboratory model was designed to replicate a human trachea. Thick secretions had the highest percentage of mean recovery representative of evacuation efficiency of SSs (mean recovery of 86%). The suction pressure of 30 mmHg had the highest overall mean of secretion recovery (83%) across all viscosity types and amounts. This study demonstrated that higher viscosity secretions were easier to evacuate than lower viscosity secretions when 30-mmHg suction pressure was applied. Management of secretion viscosity may assist in secretion removal and delay VAP development. With increased understanding of the molecular structure of SSs, there is the potential that clinicians will be able to manipulate secretion viscoelastic properties to maximize evacuation efficiency of the secretions. Further research is needed to identify safe suction pressures for optimal evacuation of SSs in human subjects.

Clinical Nursing Research↗
PubMed2002

Effect of amylase-rich flour (ARF) treatment on the viscosity of fermented complementary foods.

Grains of cowpea and maize and slices of fresh cassava, cocoyam, plantain, and yam were steep-fermented in water, while flours from the same plant materials were fermented by backslopping for 24 to 30 hours. The pH and apparent viscosity of the gruels from the resulting flours were determined. Loss in weight due to fermentation was higher in fresh tubers than in dry grains. The pH of the flours decreased during fermentation. Measurements showed that the apparent viscosity only of gruels from flours produced by backslopping decreased after 24 hours. The apparent viscosity of gruels from steep-fermented flours was higher than that of the unfermented flours and those produced by backslopping. The apparent viscosity reduction of gruels from steep-fermented flours using amylase-rich flour (ARF) from five-day white sorghum malt was better with the prepared gruels than when applied to the flour-in-tap-water suspension before it was used to prepare gruels. Viscosity reduction using ARF was also better with the fermented gruels than with gruels from unfermented flours. The implications of these results for the formulation of complementary flour blends for infant feeding are discussed.

Amylases↗
PubMed2006

Mechanics of nectar feeding in the orchid bee Euglossa imperialis: pressure, viscosity and flow.

The orchid bee Euglossa imperialis sucks nectars through a slender proboscis. I tested how nectar properties influence this suction pressure and whether ambient air pressure sets the upper limit for suction feeding. Nectar intake rate was measured as a function of sucrose concentration (5-75% w/w), nectar viscosity (2-80 mPa s), and ambient pressure (101-40 kPa). Intake rate declines from about 1.2 mul s(-1) to 0.003 mul s(-1) as sucrose concentration increases from 15% to 65% sucrose. When sucrose concentration is held at 25% while viscosity increases from 2 to 80 mPa s, intake rate declines. When viscosity is held at 10.2 mPa s (the viscosity of 50% sucrose) while sucrose concentration increases from 5% to 50%, intake rate remains constant. Intake rate was limited by a reduction in ambient pressure at all nectar concentrations. Assuming a rigid proboscis, the Hagen-Poiseuille equation suggests that suction pressure increases with viscosity from 10 kPa at 5% sucrose to 45 kPa at 65% sucrose. However, because intake rate declined by the same fraction under hypobaria (40 kPa) at all sucrose concentrations, the euglossine bee proboscis may be better described as a collapsible tube: expanding or collapsing depending on the flow rate, the pressure gradient along the proboscis, and circumferential forces imposed by the proboscis walls.

Animals↗
PubMed2005

Calculation of the viscosity of binary liquids at various temperatures using Jouyban-Acree model.

Applicability of the Jouyban-Acree model for calculating absolute viscosity of binary liquid mixtures with respect to temperature and mixture composition is proposed. The correlation ability of the model is evaluated by employing viscosity data of 143 various aqueous and non-aqueous liquid mixtures at various temperatures collected from the literature. The results show that the model is able to correlate the data with an overall percentage deviation (PD) of 1.9+/-2.5%. In order to test the prediction capability of the model, three experimental viscosities from the highest and lowest temperatures along with the viscosities of neat liquids at all temperatures have been employed to train the model, then the viscosity values at other mixture compositions and temperatures were predicted and the overall PD obtained is 2.6+/-4.0%.

Models, Chemical↗
PubMed2005

Single high-dose intravenous immunoglobulin therapy for kawasaki disease increases plasma viscosity.

BACKGROUND: Intravenous immunoglobulin therapy, widely used for various autoimmune and systemic inflammatory diseases including Kawasaki disease (KD), is occasionally associated with thromboembolic adverse effects caused by an abrupt increase in blood viscosity. Scarce information is available, however, regarding the effect of single high-dose immunoglobulin therapy for KD on blood viscosity. METHODS AND RESULTS: Eleven boys and 5 girls (mean age: 2.1 years) with acute-phase KD underwent single high-dose immunoglobulin therapy. Plasma viscosity before the treatment was 1.18 centipoises (SD = 0.06), but it significantly rose to 1.34 centipoises (SD = 0.06) (p < 0.001). Multiple regression analysis revealed that, among various factors including hematocrit, plasma concentrations of total protein, immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM), only plasma IgG concentration was included in the model to explain plasma viscosity (R2 = 0.59, p < 0.001). CONCLUSIONS: Single high-dose regimen for acute-phase KD increases blood viscosity and therefore might increase the risk of thromboembolism.

Blood Viscosity↗
PubMed2000

Effect of dietary chitosans with different viscosity on plasma lipids and lipid peroxidation in rats fed on a diet enriched with cholesterol.

To investigate the effect of dietary chitosan on lipid metabolism, male SD (Sprague-Dawley) rats were fed a cholesterol-enriched diet containing 5% cellulose (CE), 5% chitosan (CCS; high viscosity), or 5% chitosan (FCS; low viscosity) for 4 weeks. The two types of chitosan with a comparable degree of deacetylation had a different molecular weight and intrinsic viscosity. Significantly (p < 0.05) lower plasma total cholesterol, LDL-cholesterol and VLDL-cholesterol concentrations were observed in the rats fed on the chitosan diets. In addition, chitosan significantly increased the fecal cholesterol and triglyceride contents. Although no significant difference in body weight was found among the dietary groups, the rats fed on the chitosan diets had lower relative liver weight when compared with those fed on the cellulose diet. Both of the chitosan groups had significantly lower liver total lipid and total cholesterol contents compared to the cellulose group, although the FCS group was less effective. The plasma and liver thiobarbituric acid reactive substances (TBAR) values were similar in the CE and FCS groups, while the CCS group had increased liver TBAR values. Although a significant increase in liver glucose-6-phosphate dehydrogenase activity was observed in the CCS group, no significant change was found in the FCS group. The observed influence of chitosans with different viscosity on the plasma lipid level, liver lipids and lipid peroxidation suggests that, while the hypocholesterolemic action of chitosans with different viscosity was similar, changes in the liver lipids and liver peroxidation status depended on their molecular weight when the deacetylation degree was comparable.

Animals↗
PubMed2006

Optical fiber-based fluorescent viscosity sensor.

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Biosensing Techniques↗
PubMed1977

Apparent viscosity of materials used for making edentulous impressions.

The viscosity of commercially available impression materials used for making edentulous impressions was determined as a function of time and rotational speed. The impression materials studied showed large differences in viscosity and could be ranked into three groups. The values for one group--Plastogum, Ackerman cement (1:1 powder-to-liquid ratio), and light-bodied Permlastic--ranged from 23,800 cp to 57,200 cp. The viscosity values for a second group--Unilastic, syringe Elasticon, Luralite, and Coe-Flo--ranged from 92,200 cp to 107,000 cp. For a third group--Omniflex, Jeltrate, and Ackerman cement (2:1 powder-to-liquid ratio)--the viscosity values ranged from 239,000 cp to 257,000 cp. Light-bodied Permlastic, Ackerman cement (1:1 powder-to-liquid ratio), Jeltrate, and syringe Elasticon functioned as Newtonian liquids immediately after mixing. All other materials were non-Newtonian in behavior. The viscosity of most impression materials increased dramatically with time; the only exceptions were the zinc oxide-eugenol impression materials.

Alginates↗
PubMed1988

[Effects of local vibration exposure on whole blood viscosity in rats].

To investigate the relationship between vibration hazards and blood viscosity, vibration exposure experiments were conducted. The rat's hind limbs were continuously exposed to local vibration (60 Hz, 5 G) for 4 h. The exposed group showed a slightly lower blood viscosity and plasma fibrinogen in the blood obtained immediately after exposure when compared with the control group. However, in the blood obtained 18 h after exposure, there was no significant difference in the levels of whole blood viscosity and plasma fibrinogen between the exposed group and the control group. Hematocrit was not affected by this exposure. These results indicate that the decrease in the levels of whole blood viscosity induced by local vibration exposure is transient and that some relationship exists between changes of whole blood viscosity and those of plasma fibrinogen.

Animals↗
PubMed1983

Effect of high osmotic media on blood viscosity and red blood cell deformability.

Effects of high osmotic media on the shape and deformability of RBC were examined for determining increasing factors of blood viscosity. Dog blood and Urographin (a hypertonic contrast medium) were used; the plasma osmolality was changed by Urografin suspended in blood. The viscosity was measured for normal RBC and glutaraldehyde-treated RBC suspensions with a cell volume concentration. The RBC deformability was evaluated from the difference in viscosity between the two suspensions. It was shown that normal RBC suspension increased the viscosity with increase in osmolality at high shear rate; hardened RBC suspension decreased the viscosity with increase in osmolality. It was concluded that the RBC deformability decreased with increasing osmolality.

Animals↗
PubMed1989

The role of mucus gel viscosity, spinnability, and adhesive properties in clearance by simulated cough.

We investigated the role of the viscoelastic and adhesive properties of mucus gel simulants on the clearance of mucus by simulated cough. Mucus-like gels with widely varying viscoelastic properties were prepared from polysaccharides crosslinked with sodium borate. Cough was simulated by opening a solenoid valve connecting a model trachea to a pressurized tank. The clearance of gels lining the model trachea was quantified by observing marker particle transport. Viscosity elastic modulus, relaxation time and yield stress were measured with a steady-shear viscoelastometer. Spinnability (thread formation) was determined with a filancemeter. Adhesivity (surface tension) was measured by the platinum ring technique. The viscoelastic and adhesive properties of the mucus gel simulants spanned the ranges observed for bronchial secretions from patients with COPD. The relationship between simulated cough clearance and the viscoelastic and adhesive properties of the gels was analyzed by stepwise linear regression of the non-zero data matrix. The major independent variable relating to clearance was viscosity. Secondary, but highly significant dependences, were also found for spinnability and adhesivity. Elastic modulus, relaxation time and yield stress had no independent effect on cough clearance over the investigated range. The results indicate that, in the absence of airway surface liquid, cough-type clearance relates primarily with mucus gel viscosity. For a given viscosity, clearance is also impaired by spinnability, i.e. the capacity of the mucus to form threads. At constant viscosity and spinnability, clearance is further impaired by an increase in the adhesivity of the mucus. The negative dependence of each of these physical factors can be rationalized in terms of their inhibitory effect on wave formation in the mucus lining layer during high velocity airflow interaction.

Adhesiveness↗
PubMed1990

Blood viscosity and optimal hematocrit in narrow tubes.

Blood viscosity in normal adults was measured in glass tubes with diameters of 50, 100 and 500 microns for a wide range of adjusted feed hematocrits (15-70%). Blood viscosity decreased at each of the adjusted feed hematocrits when going from a 500-micron tube to a 50-micron tube. The viscosity reduction increased with increasing hematocrit. The steepness in the hematocrit-viscosity curves decreased with decreasing tube diameter. Erythrocyte transport efficiency (hematocrit/blood viscosity) was calculated to estimate the optimal hematocrit for oxygen transport. Optimal hematocrit averaged 38% in 500-micron tubes, 44% in 100-micron tubes and 51% in 50-micron tubes. Our results suggest that the strong Fåhraeus-Lindqvist effect at high hematocrits may help to maintain oxygen transport in polycythemic patients as long as the driving pressure is sufficient.

Adult↗
PubMed1993

An in vitro assay for prediction of broiler intestinal viscosity and growth when fed rye-based diets in the presence of exogenous enzymes.

A two-stage in vitro assay procedure was developed for predicting the efficacy of microbial enzyme sources in rye-based diets for broiler chicks. The procedure uses the complete diet as substrate to predict the in vivo intestinal viscosity and final weight of birds fed such diets. The optimum conditions for maximizing in vitro viscosity of a rye-based diet consisted of digesting .6 g of diet (ground through a 1-mm screen) in .9 mL of .1 N HCl containing 2,000 U pepsin/mL for 45 min at 40 C. At the end of this incubation phase, .3 mL 1 M NaHCO3 containing 8 mg pancreatin/mL (8 x USP) was added and the tube sealed and incubated for 2 h with intermittent vortexing. The digesta was then centrifuged (12,700 x g) and the supernatant collected for viscosity analysis using a digital viscometer. This assay was used for a rye-based diet containing either 0, .1, .2, .4, .8, or 1.6% of a xylanase source (experimental Trichoderma longibrachiatum product). The results were compared to weight and intestinal viscosity proximal and distal to Meckel's diverticulum of broilers (19 days of age) that had been fed these diets. The in vitro assay accurately predicted the in vivo intestinal viscosity (proximal r2 = .758, P < .0001, distal r2 = .667, P < .0001) and final weight of these birds (r2 = .660, P < .0001). The data suggest that the in vitro assay is a reliable assay for assessing the growth-promoting ability of an enzyme preparation in chicks fed rye-based diets.

Animal Feed↗
PubMed2004

Investigation of preferred viscosity of irreversible hydrocolloid on preliminary impression for edentulism.

This study aims to investigate the preferred viscosity of irreversible hydrocolloid used in the preliminary impression for edentulism. Thirteen modalities of irreversible hydrocolloid were prepared by changing the W/P ratio. Discrimination test for the preferred viscosity was performed on 11 prosthodontists (10.4+/-5.3 years of prosthetic experience). The parameter of discrimination test (P%) was calculated as the ratio of the number of adequate tests to the total number of tests. The P% and apparent viscosity coefficient (eta a) values measured by rheometer demonstrated good correlation (Y = -35.8X2 + 118.4X - 22.8, r=0.86, p<0.01). Prosthodontists could judge the preferred viscosity based on their clinical experiences. On the preliminary impression for edentulism, the preferred viscosity demonstrated in vitro using a polyurethane maxilla model was 1.21 x 10(3) Pa x s.

Alginates↗
PubMed2000

Plasma viscosity, fibrinogen and the metabolic syndrome: effect of obesity and cardiorespiratory fitness.

The association between both plasma viscosity and fibrinogen concentration with clustering of metabolic risk markers was examined within a cross-sectional study of employed middle-aged men. Analyses were performed on a subsample of 629 non-smokers (46.7+/-7.8 years) without diabetes. The effect of obesity and cardiorespiratory fitness on these haemorheological parameters and their association with the metabolic syndrome was also investigated. The cohort was grouped by the number of metabolic markers present. Metabolic markers included high-density lipoprotein-cholesterol (<1.13 mmol/l), triglycerides (> or =1.805 mmol/l), glucose (> or =5.5 mmol/l) and diastolic blood pressure (> or =90 mm Hg). The age-adjusted odds ratio for hyperviscosity (> or =1.67 mPa/s) was 2.08 [95% confidence interval (CI), 1.06-4.05; P = 0.031] for the subjects with the metabolic syndrome (three or more metabolic markers) when compared with those with no metabolic abnormalities. The comparable age-adjusted odds ratio for hyperfibrinogenaemia (> or = 3.47 g/l) was non-significantly higher at 1.69 (95% CI, 0.87-3.27; P = 0.119). The mean age-adjusted plasma viscosity level and the prevalence of hyperviscosity increased significantly from 1.629 to 1.692 mPa/s (P = 0.0005) and from 21.0 to 36.0% with accumulating metabolic markers (P = 0.006). Plasma viscosity and fibrinogen concentration both increased with higher quartiles of skinfolds (P = 0.003 and P = 0.01, respectively) following adjustment for age, lipids and leucocyte count. Plasma viscosity was also significantly lower with higher levels of predicted maximum oxygen consumption (VO2max) (P = 0.0005). The odds ratio for hyperviscosity in subjects with the metabolic syndrome as compared with those with no metabolic markers was attenuated following adjustment for age, sum of skinfolds and predicted maximum oxygen consumption (VO2max) (1.44; 95% CI, 0.72-2.90; P = 0.307). These cross-sectional results suggest that plasma viscosity is associated with increased clustering of metabolic markers in middle-aged men of high socio-economic status. Obesity and poor cardiorespiratory fitness may be important in the development of haemorheological abnormalities associated with the metabolic syndrome.

Adult↗
PubMed2000

The relationship between plasma viscosity and cholesterol in postmenopausal women on hormone replacement therapy.

In women, cardiovascular morbidity and mortality sharply increase after the onset of menopause. There is substantial evidence that hormone replacement therapy (HRT) may decrease the risk of coronary heart disease; however the mechanism is unclear. We investigated the relationship between HRT and plasma viscosity as well as cholesterol levels in postmenopausal women. 30 women were using HRT (HRT users), and 30 women were not using HRT (non-users). According to the classification of their plasma cholesterol levels, 30 women were hypercholesterolemic levels (hypercholesterolemic users n = 15, and hypercholesterolemic non-users n = 15), and the others were normocholesterolemic levels. While the highest plasma viscosity was measured in hypercholesterolemic users (1.291 +/- 0.053 cP), the lowest plasma viscosity was measured in normocholesterolemic users (1.127 +/- 0.056 cP). There was a significant correlation between plasma viscosity and cholesterol levels in the women on HRT (r = 0.76, p < 0.001). We have not found a difference neither in fibrinogen levels nor in triglycerides between users and non-users. These data demonstrated that HRT has beneficial effect on plasma viscosity; mainly in normocholesterolemic post menopausal women.

Blood Viscosity↗
PubMed1975

Elevation of blood viscosity, aggregation of red cells, haematocrit values and fibrinogen levels with cigarette smokers.

A study of blood viscosity factors was carried out on male smokers and non-smokers (125 volunteers) in the age group 45 to 55 years. The smoker's group exhibited elevated haematocrit values, fibrinogen levels and blood viscosity (P less than 0-025), and increased aggregation of red cells and plasma viscosity (P less than 0-005). Especially in the dependence of aggregation of red cells on the level of fibrinogen, the smokers of blood group O showed higher values than smokers of blood group A (P less than 0-01). Elevation of blood viscosity factors and functions in smokers suggests that pathways to ischaemia and thrombosis, to which smokers are more prone than non-smokers, may move through the blood high-viscosity syndromes.

Blood Sedimentation↗