Rheodyn SSD Research Articles

Temperature dependency of whole blood viscosity and red cell properties in desert ungulates: Studies on scimitar-horned oryx and dromedary camel.

The dromedary camel and the oryx antelope are exposed to excessive heat and solar radiation in their desert habitat. Desertification of areas with by now little rainfall may occur eventually. Well-adapted large animal species show us what is needed to survive in scorching regions. Four scimitar-horned oryx antelopes (Oryx dammah), 10 camels (Camelus dromedarius), nine South African Merino sheep, and 17 Nguni cows were tested for RBC aggregation, RBC elongation, and plasma viscosity. The temperature dependency of blood viscosity was tested in 10 camels and compared to human reference values. Unlike sheep, Nguni cow, and dromedary camel, oryx RBCs aggregate in native plasma (M0:5.2 (3.3/6.7); M1:18.1 (16.7/27.9); Myrenne MA1). Elongation indices of oryx RBCs were intermediate to low (EImax: 22.6 (19.2/25.3); SS1/2 3.67 (2.52/4.95); Rheodyn SSD). Camel RBCs did not display the typical SS/EI curve by rotational ektacytometry. In-vitro blood viscosity (Physica MCR302) was lower in camels than in human blood at equal hematocrit. A decrease of temperature had only little effect on camel blood. At 10 s−1, blood viscosity in camel increased from 2.18mPa*s (2.01/2.37) at 42◦C to 4.39mPa*s (4.22/4.51) at 12◦C. In human blood, viscosity ranged from 8.21mPa*s (6.95/8.25) at 37◦C to 15.52mPa*s (14.25/16.03) at 12◦C. At 1000 s−1, blood viscosity in camel ranged from 2.00mPa*s (1.95/2.04) at 42◦C to 3.98mPa*s (3.88/4.08) at 12◦C. In human blood, viscosity ranged from 5.35mPa*s (4.96/5.87) at 37◦C to 11.24mPa*s (10.06/11.17) at 12◦C. Desert ungulates may need RBC membranes, which are fortified to withstand changes in osmolality during dehydration-rehydration cycles. This reduces RBC deformability. Dromedary camel blood does not undergo stark changes in viscosity with changes in temperature. Therefore, blood fluidity could be rather maintained during the day and night cycle. This should reduce the need of the vascularity to rhythmically adapt to changing shear forces when camels experience heterothermy.

Blood rheology during normal pregnancy.

Recent studies have shown increased RBC aggregation and no difference in plasma viscosity in the presence of markedly lower hematocrit in women at term compared to non-pregnant women. Little is known about the outcome of blood rheological parameters and red blood cell (RBC) deformability particularly in the course of normal pregnancy. During a 36 months interval 1.913 blood samples were randomly collected from a total of 945 pregnant women in the course of their pregnancy (n = 1.259) and during puerperium (upto 1 week; n = 654). Next to the blood count, hemorheological parameters including red blood cell (RBC) -aggregation (stasis E0; low shear E1), -deformability (low, moderate and high shear conditions) and plasma viscosity (pv) were assessed. Plasma viscosity (pv) was examined using KSPV 1 Fresenius, RBC aggregation (stasis: E0 and low shear: E1) using MA1-Aggregometer; Myrenne and RBC deformability (def) was determined by Rheodyn SSD Diffractometer, Myrenne, Roetgen, Germany were tested. In some of these women laboratory results prior to pregnancy (n = 145) were available which were compared with those during pregnancy. Mean maternal pv remained unchanged within each trimester and compared to the values before pregnancy and during early puerperium (Range of means: 1.18-1.20 mPa S). In contrast, RBC agg (E0 and E1) was markedly higher in the 2nd (21.8 ± 7.0 and 28.9 ± 9.4; p < 0.001) and 3rd trimester (18.74 ± 8.4 and 28.2 ± 9.4; p < 0.01) compared to the values before pregnancy (16.4 ± 6.4 and 20 ± 7.5) and during 1st trimester (17.49 ± 6.5 and 22.4 ± 7.4). There was a stat. significant temporary reduction in RBC def. under all shear rate conditions during 2nd trimester compared to the values before pregnancy which remained significantly lower during 3rd trimester only under high shear rates.An increase RBC agg was stat. significantly inversely correlated with reduced RBC def being most pronounced under low shear rate conditions. While RBC rigidity was stat. significantly correlated with higher hematocrit values there was only a weak correlation between RBC agg and haematocrit (E0: r = -0.084; p = 0.03; E1: r = -0.06; p = 0.1). Pv was not correlated with haematocrit or RBC def but stat. significantly correlated with RBC agg. Blood rheological changes manifest during 1st trimester, and fairly remain unchanged during 2nd trimester until term. Physiologic hemodilution and increasing hypercoagulability is accompanied by high RBC -aggregation and - rigidity during 2nd trimester while plasma viscosity remains nearly unaffected throughout normal pregnancy.

Red blood cell distribution width and erythrocyte deformability in patients with acute myocardial infarction

Increased RDW has been found to be a marker of adverse outcomes in cardiovascular disease (CVD), although the exact mechanism remains unclear. Recently, several authors have found that higher RDW is associated with decreased erythrocyte deformability, which can impair blood flow through microcirculation, a fact which may explain the increased risk for CVD events associated with elevated RDW. The aim of the present study was to investigate the association between RDW and erythrocyte deformability in patients with acute myocardial infarction (AMI). The study group comprised 60 AMI patients and 72 gender- and age-matched controls, in whom erythrocyte deformability was determined by means of the elongation index (EI) in a Rheodyn SSD, along with haematological, biochemical and inflammatory parameters. Patients showed higher RDW (p = 0.012) and lower EI (p < 0.05) than controls. When anaemic patients were removed from the study, AMI showed still lower EI than controls (p < 0.05), but no differences in RDW were observed (p = 0.141). RDW correlated inversely with haematimetric indices (p < 0.001), but not with inflammatory and biochemical parameters (p > 0.05). EI correlated inversely with Hb, MCHC (p < 0.001) and directly with MCV (p < 0.05). EI also correlated inversely with glucose (p < 0.05) and directly with HDL-cholesterol (p < 0.05). The multivariate regression model showed that only MCV and Hb were independent predictors of RDW (beta coefficients: -0.383, -0.208; p < 0.001, p = 0.050, respectively). In addition, MCV, MCHC and hyperlipidaemia were independent predictors of EI (beta coefficients: 0.366, -0.533, -0.192; p < 0.001, p < 0.001, p = 0.019 respectively). In AMI patients, increased RDW is not related with EI, so this mechanism does not seem to be responsible for an increased CDV risk in these patients.

Nitric oxide metabolites and erythrocyte deformability in a group of subjects with obstructive sleep apnea syndrome

Our aim was to evaluate nitric oxide metabolites (nitrite and nitrate), expressed as NOx, and erythrocyte deformability, expressed as elongation index, in a group of subjects with obstructive sleep apnea syndrome (OSAS). We enrolled 48 subjects (36 men and 12 women; mean age 50.3±14.68 yrs) with OSAS diagnosed after a 1-night cardiorespiratory sleep study. OSAS severity was assessed evaluating the apnea/hypopnea index (AHI) and subjects were subdivided in two subgroups: Low (L=AHI<30) and High (H=AHI>30). NOx was examined converting nitrate into nitrite with a nitrate reductase and then assessing nitrite with spectrophotometry after the addition of Griess reagent. The elongation index was obtained using the diffractometer Rheodyn SSD of Myrenne at shear stresses of 30 and 60 Pa and it was expressed as elongation index (EI). We found no difference in NOx among the entire group of OSAS subjects and normal controls, while we observed a NOx decrease in the H subgroup in comparison with L subgroup, but not in comparison with normal controls. We noted a significant decrease in EI at each shear stress in the entire group and also in the two subgroups in comparison with controls. The decrease in NO bioavailability and in erythrocyte deformability might contribute to explain the increased cardiovascular risk in OSAS subjects.

Erythrocyte deformability and aggregation in homozygous sickle cell disease

Rheological properties of homozygous sickle cell anaemia (SCA) show marked heterogeneity, which may be explained in part by the concomitance of alpha genotypes or beta haplotypes, along with hydroxurea (HU) treatment. To further clarify this issue, in 11 homozygous patients with SCA in the steady state and in 16 healthy controls, we analysed erythrocyte deformability (ED) in a Rheodyn SSD by means of the Elongation Index (EI) at 12, 30 and 60 Pa, and erythrocyte aggregation at stasis (EA0) and at 3 sec-1 (EA1) in a Myrenne aggregometer along with fibrinogen, biochemical and haematological parameters. When compared with controls, homozygous (SS) patients showed a lower EI at all the shear stresses tested (p < 0.01) and higher EA0 (p < 0.014), but not higher EA1 (p = 0.076). Fibrinogen did not show statistical differences (p = 0.642). In the Spearman's correlation IE60 correlated inversely with Hb S (p < 0.05) and directly with MCV, MCH and Hb F levels (p < 0.01). EA0 correlated inversely with MCV, MCH, Hb F (p < 0.01) and directly with Hb S (p < 0.05). HU treatment improved EI and EA0, but not EA1. This paradoxical behaviour of HU on erythrocyte aggregation merits further research to be clarified.

Erythrocyte deformability and psoriasis

Psoriasis, a systemic immunomediated disorder, is associated with increased cardiovascular risk, although the contribution of rheological alteration to this risk has been seldom analyzed. We have determined erythrocyte deformability in 91 patients with psoriasis and in 101 sex- and age-matched control subjects by means of the Rheodyn SSD, along with hematological, biochemical and inflammatory parameters. Although psoriatic patients showed higher BMI, waist, triglyceride, C-reactive protein levels, neutrophils count and lower HDL-cholesterol (P < 0.001), no differences in the elongation index and in any of the shear stresses tested (12, 30, 60 Pa) were observed (P > 0.05). The results of the present study indicate that patients with psoriasis do not present impaired erythrocyte deformability. Therefore this rheological parameter does not seem to be involved in the higher cardiovascular risk characterizing these patients.

Fibrinogen effects on erythrocyte nitric oxide mobilization in presence of acetylcholine

AimsThe objectives of this study were to evaluate the effects of high fibrinogen concentration on erythrocyte deformability on mobilization of nitric oxide (NO) and of its metabolites in the presence of acetylcholine (ACh) in healthy human blood samples. Main methodsLevels of NO were evaluated by amperometric method. Nitrite, nitrate and S-nitrosoglutathione (GSNO) were measured using the spectrophotometric Griess reaction. Erythrocyte deformability was determined using the Rheodyn SSD laser diffractometer. Key findingsIn the presence of high concentrations of fibrinogen and ACh (10μM) in the blood samples from healthy humans the erythrocyte nitrites, nitrates and GSNO concentrations increased without significant changes in NO efflux. Mobilization of NO in erythrocytes' presence was enhanced in the presence of ACh and high fibrinogen levels. SignificanceThese results suggest that during inflammation when both ACh and high levels of fibrinogen are present, NO delivery by erythrocytes might be compromised by their NO scavenging ability that acts as a compensatory mechanism against the overproduced NO by endothelial inducible nitric oxide synthase.

Erythrocyte deformability in naïve HIV-infected patients

HIV-infected patients are at increased cardiovascular risk. Although several studies have analyzed the hemorheological profile in these patients, studies dealing with erythrocyte deformability are scarce. Moreover, studies have been performed in HIV patients on antiretroviral treatment which may influence this rheological parameter. We analyzed erythrocyte deformability (Elongation Index) at 12, 30 and 60 Pa by means of the Rheodyn SSD in 34 naïve HIV-infected patients (22 males and 12 females) and 34 HIV negative control subjects (24 males and 10 females). Erythrocyte indices (MCV, MCH, MCHC), reticulocytes, plasma lipids, iron, folic acid, vitamin B12 and hepatic enzymes were also determined. When compared with controls, naïve HIV-infected patients showed lower total cholesterol, iron, bilirubin and folic acid (p = 0.009, p = 0.003, p = 0.004, p = 0.004, respectively) and higher triglycerides (TG), aspartate aminotransferase (AST) and gamma glutamyl transferase (γGt) levels (p = 0.017, p = 0.042, p = 0.004, respectively). In the multivariate regression analysis, MCV, γGt and triglycerides were independent predictors of EI60. Neither erythrocyte indices nor reticulocyte count showed differences (p > 0.05). No differences in the Elongation Index at any of the shear stresses tested (12, 30, 60 Pa) were found (p > 0.05). The results of the present study indicate that naïve HIV-infected patients not on antiretroviral treatment do not present decreased erythrocyte deformability when compared with HIV negative control subjects.

Rheological red blood cell behaviour in minor α-thalassaemia carriers

Although several studies have been published regarding rheological behaviour of red blood cells in beta and delta-beta thalassaemia traits, little information about erythrocyte deformability in alpha-thalassaemia carriers is available. We aimed to determine erythrocyte deformability in heterozygous (silent, -α/αα) and homozygous (minor alpha-thalassaemia, -α/-α) carriers of the alpha-thalassaemia trait for the alpha 3.7 deletion, the most common in our geographical area. We evaluated erythrocyte deformability by means of the elongation index (EI) in a Rheodyn SSD at 12, 30 and 60 Pa, along with basic haematological cell count, erythrocyte indices, reticulocytes, plasma lipids and iron metabolism parameters in 36 (18 women, 18 men) alpha-thalassaemia carriers (17 heterozygous, 19 homozygous) and 36 healthy subjects (23 women, 13 men). The molecular diagnosis of the alpha 3.7 deletion was evaluated by a PCR-based method. Alpha-thalassaemia carriers presented higher red blood cell counts, RDW-CV (p < 0.001) and lower haemoglobin, MCV, MCH and MCHC (p < 0.001) than controls. EI was statistically lower at 12, 30 and 60 Pa in cases than in controls (p = 0.001, p = 0.002, p = 0.010, respectively). No differences in either elongation indices or haematimetric values were observed when comparing silent heterozygous and minor homozygous alpha-thalassaemia carriers (p > 0.05). Pearson's bivariate correlation showed that EI60 correlated positively with haemoglobin and MCV, MCH, MCHC (p < 0.01), but negatively with ferritin (p< 0.05) and RDW-CV (p< 0.01). In the multivariate regression analysis, MCV (p = 0.001) and haemoglobin (p < 0.001) predicted EI60, with this model accounting for around 43% of variation in EI60 (R2 = 0.427). Alpha-thalassaemia carriers phenotypically showed mild microcytosis and hypochromia, irrespectively of them being silent heterozygous or minor homozygous alpha-thalassaemia carriers, which is associated with decreased erythrocyte deformability.

Association between hemorheological alterations and metabolic syndrome

The contribution of hemorheological alterations in the prothrombotic condition in patients with metabolic syndrome (MS) remains a question of debate. We aimed to determine the association between MS and hemorheological parameters by means of a case-control study in 61 MS patients and 89 controls without MS. We determined blood viscosity at 230 s(-1) (Brookfield DVIII viscosimeter); plasma viscosity (Fresenius capillary plasma viscosimeter); erythrocyte aggregation at stasis and 3 s(-1) (MA-1 erythrocyte aggregometer); erythrocyte deformability (Rheodyn SSD at shear stresses of 12, 30 and 60 Pascals) and fibrinogen, along with anthropometric, lipidic and inflammatory parameters. MS patients showed increased blood viscosity (p = 0.018), plasma viscosity (p < 0.001), fibrinogen (p < 0.001), erythrocyte aggregation (p < 0.001), and decreased erythrocyte deformability (p = 0.033). In the multivariate regression analysis, fibrinogen and triglycerides predicted plasma viscosity and erythrocyte aggregability, whereas erythrocyte deformability was associated with alterations in the hydrocarbonate metabolism. Blood viscosity related to abdominal obesity. The logistic regression analysis revealed that of all the MS components, only hypertriglyceridemia independently predicts plasma hyperviscosity (OR 3.75 CI 1.44-9.77 p = 0.007) and erythrocyte hyperaggregability (OR 2.41 CI 1.00-5.80 p = 0.050). Erythrocyte hyperaggregability (EA > 8.23) and hyperfibrinogenemia (fibrinogen > 358 mg/dL) were independent predictors of MS: OR 3.34, 95% CI 1.40-7.93, p = 0.006 and OR 2.42 95% CI 1.04-5.66, p = 0.041, respectively. We conclude that MS is associated with an altered hemorheological profile related to inflammatory, lipidic and glucose intolerance parameters which could favor the development of thrombo-embolic and athero-thrombotic events in MS patients.

Erythrocyte deformability in morbid obesity before bariatric surgery. Influence of abdominal obesity

Although there are several studies dealing with erythrocyte deformability (ED) in obese patients, research on this topic in morbidly obese subjects is scarce. In these studies ED seems to be decreased, although the cause remains unknown. A case-control study in 76 morbid obese subjects (23 women and 53 men, aged 44 ± 13 years) and in 79 normal-weight controls (30 women and 49 men, aged 43 ± 13 years) was undertaken. ED has been determined by ektacytometric techniques in a Rheodyn SSD, by means of the elongation index (EI) at 12, 30 and 60 Pascals, along with anthropometric, lipidic, metabolic and inflammatory parameters. EI was statistically lower in morbidly obese subjects than in controls at all the shear stresses tested (EI12: 47.3 ± 2.14 vs. 47.9 ± 2.07; p = 0.047, EI30: 52.16 ± 2.1 vs. 53.12 ± 1.4; p = 0.007, EI60: 53.9 ± 2.4 vs. 55.2 ± 2.50; p = 0.001) as were anthropometric lipidic and inflammatory parameters (p < 0.001). In the bivariate correlation EI60 correlated negatively with most anthropometric, lipidic and inflammatory parameters. However, in the multivariate analysis, the case-control status was not significantly associated with EI60 and only triglycerides, glucose, hs-CRP and waist circumference were independently associated with EI60, constituting independent predictors of altered ED although, waist circumference, showed the highest statistical significance (p = 0.007). ED is decreased in morbidly obese subjects associated with insulin resistance and inflammation parameters although abdominal obesity seems to be of paramount importance in altering this rheological parameter.

Erythrocyte deformability in macrocytosis determined by means of ektacytometry techniques

There is little information regarding the behaviour of red blood cell deformability in macrocytosis. We have determined in 114 patients with macrocytosis (MCV > 97 fL) and in 115 age and sex-matched subjects with normocytosis (VCM < 97 fL) erythrocyte deformability by means of ektacytometric techniques (Rheodyn SSD) measuring the erythrocyte elongation index (EEI) at 12, 30 and 60 Pa. Patients with macrocytosis showed statistically higher EEI at all the shear stresses tested when compared with controls (p < 0.001). When patients with macrocytosis were classified according to their main diagnosis as hepatic or renal disease, HIV and miscellaneous, 66.7%, 41.7%, 36.7% and 33.3% of patients, respectively, showed a EEI 60 higher than 61.8% (mean value of the control group + 2 SD). Linear regression analysis demonstrates that MCV, bilirubin, triglycerides and alanine aminotransferase were the main variables influencing EEI 60. An increased surface/volume ratio of the red blood cells may be the main cause related with a higher erythrocyte deformability in a relevant percentage of macrocytosis. Further research is required to confirm our findings by designing case-control pathology-specific studies.

Comparison of three commercially available ektacytometers with different shearing geometries

In December 2008, the International Society for Clinical Hemorheology organized a workshop to evaluate and compare three ektacytometer instruments for measuring deformability of red blood cells (RBC): LORCA (Laser-assisted Optical Rotational Cell Analyzer, RR Mechatronics, Hoorn, The Netherlands), Rheodyn SSD (Myrenne GmbH, Roetgen, Germany) and RheoScan-D (RheoMeditech, Seoul, Korea). Intra-assay reproducibility and biological variation were determined using normal RBC, and cells with reduced deformability (i.e., 0.001-0.02% glutaradehyde (GA), 48 degrees C heat treatment) were employed as either the only RBC present or as a sub-population. Standardized difference values were used as measure of the power to detect differences between normal and treated cells. Salient results include: (1) All instruments had intra-assay variations below 5% for shear stress (SS)>1 Pa but a sharp increase was found for Rheodyn SSD and RheoScan-D at lower SS; (2) Biological variation was similar and markedly increased for SS<3-5 Pa; (3) All instruments detected GA-treated RBC with maximal power at 1-3 Pa, the presence of 10% or 40% GA-modified cells, and the effects of heat treatment. It is concluded that the LORCA, Rheodyn SSD and RheoScan-D all have acceptable precision and power for detecting reduced RBC deformability due to GA treatment or heat treatment, and that the SS range selected for the measurement of deformability is an important determinant of an instrument's power.

Effects of erythropoietin on erythrocyte deformability in non‐transfused preterm infants

Suppression of erythropoiesis due to low plasma erythropoietin levels is an important factor in the development of anaemia of prematurity. Premature infants may therefore be treated with recombinant human erythropoietin (rhEPO). This prospective, randomised and controlled study was designed to find out whether rhEPO treatment improves erythrocyte deformability in preterm infants. Sixteen infants were treated with rhEPO (250 IU/kg three times weekly) a total of 15 times beginning on day of life 5 whereas fifteen infants served as controls. Haemoglobin concentration, haematocrit, reticulocyte count, ferritin level and erythrocyte deformability were measured on days 5, 14, 28, 42 and 63. Erythrocyte elongation was determined as an indicator of erythrocyte deformability using a shear stress diffractometer (Rheodyn SSD) at shear forces of 0.3 to 60 Pa. Haemoglobin concentration was significantly higher on days 28 and 42 and reticulocyte percentage on day 28 in the rhEPO group compared to the controls. Serum ferritin was lower in the rhEPO group on day 28. Erythrocyte deformability was significantly increased on days 28 and 42 in the infants receiving rhEPO. We found a strong relationship between erythrocyte elongation and reticulocyte count. RhEPO markedly increases the erythropoiesis in preterm infants in the critical first weeks of life and the anaemia of prematurity is obviously reduced. The erythrocyte deformability improved under rhEPO treatment. Erythrocyte deformability was significantly related to the reticulocyte count indicating that the improvement of erythrocyte deformability was due to the formation of well-deformable young erythrocytes.

Rheological Properties of Red Blood Cells in Kidney Transplant Recipients: The Role of Lipid Profile and Type of Immunosuppresion

Introduction The main rheological properties of red blood cells (RBC) are deformability and aggregability. Deformability is one of the most important factors of RBC flow in high-shear rate areas, especially in the microcirculation. Aggregability of erythrocytes can impair circulation in low-shear rate areas. Both deformability and aggregability of RBC are abnormal in patients with renal insufficiency and after kidney transplantation. Cyclosporine (CsA) and less frequently tacrolimus (Tc) may cause hyperlipidemia and hypertension. Dobiasova et al proposed the term Atherogenic Index of Plasma (AIP), defined as a log (TG/HDL-C). Subjects with high AIP have and higher risk of cardiovascular complications due to atherosclerosis. Hence the aim of this study was to compare aggregability and deformability of RBC from kidney transplant recipients on CsA or Tc-based immunosuppression with healthy volunteers and subjects with dyslipidemia (control groups). Both control and transplant recipient groups were arbitrarily divided by value of AIP as ≤0 (AIP−) or >0 (AIP+). Deformability and aggregability of erythrocytes were measured using Rheodyn SSD and Myrenne Aggregometer, respectively. Results We observed a significant increase in aggregation index at stasis in CsA-treated patients and an increased deformability in Tc-treated patients with negative AIP. Deterioration of hemorheological properties of RBC in kidney transplant recipients was confined to an increased aggregability in CsA-treated patients regardless of AIP value. An increased deformability of RBC in Tc-treated patients with normal lipid profiles may suggest a positive effect of Tc on mechanical properties of RBC.

Organ preservation solutions impair deformability of erythrocytes in vitro

Microcirculatory disturbances are observed frequently after restoration of the circulation in transplanted organ. The exact mechanisms responsible for impaired microcirculation during reperfusion are unknown. Erythrocyte deformability is an important factor maintaining the microcirculation. Red blood cells (RBC) (diameter 8 μm) passing through narrow capillaries (diameter 3–5 μm) undergo deformation due to shear stress present in the microcirculation. RBC with impaired deformability may even plug the capillaries. Immediately after completion a vascular anastomosis and restoration of blood circulation in the transplanted organ, RBC may be intimately exposed to the preservation solution. The aim of the present study was to investigate the effect of the preservation solution on deformability of RBC. Blood from five healthy volunteers was withdrawn by venipuncture from an antecubital vein. EDTA was used as an anticoagulant. RBC were isolated by 10-minute centrifugation (2500 rpm) to separate serum and buffy coat. RBC washed in normal saline were resuspended in autologous plasma, Bretschneider's histidine-tryptophan-ketoglutarate (HTK) or University of Wisconsin solution (UW) at an hematocrit of 20% for incubation at room temperature. After 30 minutes RBC deformability was measured using the shear stress diffractometer Rheodyn SSD to calculate the elongation indexes of RBC at various shear stresses. HTK caused a decrease in the deformability indices of erythrocytes at shear stresses from 0.3 to 1.2 Pa. Erythrocytes incubated with UW solution revealed a decrease in deformability index at all investigated shear stresses. HTK causes less deterioration of erythrocyte deformability compared to UW solution.

The shear stress diffractometer Rheodyn SSD for determination of erythrocyte deformability I. Principles of operation and reproducibility

The Rheodyn SSD is an automated laser diffractometer for rapid measurement of red blood cell (RBC) deformability in small quantities of blood. RBC are suspended in a viscous medium and placed between a rotating and a stationary disk. Defined shear stresses of 0.3 to 60 Pa force the RBC to deform to ellipsoids, causing elliptical diffraction pattern of a laser beam passing through the RBC suspension. At shear stresses of 3 to 60 Pa, coefficient of variation was <3% for repeated measurements of the same blood sample. RBC deformation was not affected by the anticoagulant (no anticoagulant, heparin, EDTA, or citrate), the sample size (10 to 50 III of blood) and washing of RBC. The results show that the Rheodyn SSD is a reproducible tool to study RBC deformability in small blood samples. Copyright © 1996 Elsevier Science Ltd

The shear stress diffractometer Rheodyn SSD for determination of erythrocyte deformability II. Sensitivity to detect abnormal erythrocyte deformability

Instruments for measurement of red blood cell deformability (RBC) should be sensitive to detect both a moderate reduction in cellular deformabiltiy of the entire RBC popUlation and of a subpopulation of rigid RBC. The sensitivity of the laser diffractometer Rheodyn SSD was tested by treatment of normal RBC with increasing concentrations of glutaraldehyde, mixing of normal RBC with increasing percentages of rigid RBC, and by density separation of normal RBC. Maximum RBC elongation (at a high shear stress of 60 Pa) decreased from 60 to 8 when increasing the glutaraldehyde concentration from 0 to 0.004%. For every 10% of rigid RBC, mean RBC elongation decreased by about 10%. Density-separated RBC showed a typical deformation behavior: top cells were better deformable than bottom cells over the whole range of applied shear stresses. The results show that the Rheodyn SSD is a sensitive tool to detect abnormal RBC deformability. Copyright © 1996 Elsevier Science Ltd

Red blood cell deformability determined by the Rheodyn SSD in familial hypercholesterolemia

Red blood cell deformability determined by the Rheodyn SSD in familial hypercholesterolemia

The rheodyn SSD for measuring erythrocyte deformability

The rheodyn SSD for measuring erythrocyte deformability