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    PublicationOpen Access
    Data reduction methods for ektacytometry in clinical hemorheology
    (IOS Press, 2013) Meiselman, Herbert J.; Başkurt, Oğuz Kerim; Faculty Member; School of Medicine; 2389
    Laser-diffraction ektacytometry is a generally accepted technique for measuring RBC deformability induced by fluid shear stress (SS) and yields paired elongation index-SS data at several levels of stress. Unfortunately, comparison of results is hindered by the lack of simple indices that accurately characterize these data. Several mathematical models have been proposed, including those developed for analysis of enzyme kinetics (Lineweaver-Burk, Eadie-Hofstee) and curve fitting (Streekstra-Bronkhorst). All of these analytical approaches provide a value for cell deformation at infinite stress (EImax) and the shear stress required to achieve one-half of this deformation (SS1/2); the use of non-linear regression is essential when calculating these parameters. While the current models provide equivalent results for normal RBC if used with non-linear regression, EImax and SS1/2 are not always concordant for cells with abnormal mechanical behavior. This technical note examines such differences for three conditions: glutaraldehyde treatment, mechanical stress and non-isotonic media. It was found that none of the models yield completely satisfactory values for EImax and SS1/2, especially if there are large changes of EImax. However, the ratio of SS1/2 to EImax (SS1/2/EImax) is much less affected by these problems, has similar power (i.e., standardized difference) as SS1/2 and EImax and is more robust in reflecting alterations of deformability. We thus conclude that the SS1/2/EImax ratio can be used when reporting and comparing various populations of RBC or cells obtained from subjects having different clinical states.
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    PublicationOpen Access
    Exercise hemorheology: classical data, recent findings and unresolved issues
    (IOS Press, 2012) Connes, Philippe; Simmonds, Michael J.; Brun, Jean-Frederic; Başkurt, Oğuz Kerim; Faculty Member; School of Medicine; 2389
    The present review focuses on the past and recent knowledge in the field of exercise hemorheology and presents some unresolved issues for opening discussion. Acute exercise is associated with a rise in hematocrit which results in an increase in blood viscosity. Whereas increased blood viscosity was previously viewed as having negative consequences for cardiovascular function and aerobic performance, recent findings suggest dynamic changes in blood viscosity might be useful for vascular function during exercise by increasing nitric oxide production. Other determinants of blood viscosity are altered by exercise (e.g., decreased red blood cell deformability, increased red blood cell aggregation and plasma viscosity) and may, independent of the associated effect on blood viscosity, directly modulate aerobic capacity. However, the data published on the effects of exercise on the hemorheology are not consistent, with some studies showing decreased, unchanged, or increased red blood cell deformability/aggregation when compared with rest. These discrepancies seem to be related to the exercise protocol investigated, the population tested or the methodogy utilized for hemorheological measurements. Finally, this review focuses on the effects of training exercise training (i.e. chronic physical activity) on the hemorheological profile of healthy individuals and patients with cardiovascular and metabolic disorders.