Viscometer validation studies for routine and experimental hemorheological measurements

Prediction of Blood Viscosity Based on Usual Hematological Parameters in a Clinically Healthy Population Living in a High-Altitude City

Huamaní, Charles, William Sarmiento, Golda Córdova-Heredia, Luz Cruz-Huanca, Paulina Damián-Saavedra, and Dario Antonio. Prediction of blood viscosity based on usual hematological parameters in a clinically healthy population living in a high-altitude city. High Alt Med Biol. 23:78-84, 2022. Background and Aims: Variations in blood viscosity are mainly determined by the hematocrit level, but in residents of high-altitude cities, the hemoglobin levels and blood viscosity values are often high. We aimed to determine the blood viscosity values in clinically healthy chronic hypoxia-acclimatized individuals and establish a predictive model based on the hematocrit level and other common hematological parameters. Methods: A prospective observational study was conducted in asymptomatic young adults living in Cusco (a city located at 3,399 m). Venous blood samples were collected to determine the hemoglobin, hematocrit, and albumin and serum protein levels and blood viscosity values. Results: Altogether, 253 volunteers were included, of whom 147 (58.1%) were women. The hematological values were mean values of hemoglobin, 16.32 ± 2.0 g/dl; hematocrit, 48.12% ± 5.24%; triglycerides, 130.68 ± 90.64 mg/dl; globulin, 3.07 ± 0.36 g/dl; and mean blood viscosity, 6.17 ± 0.94 centipoises. The prediction model with the highest explained variance (R² = 68.07%) and parsimony conservation comprised hematocrit, globulin, and triglycerides [blood viscosity = hematocrit × (0.176) + globulin × (0.595) + triglycerides × (1.77/1,000) - 4.13]. Conclusions: In a population living at high altitude, the blood viscosity level is extremely high and mainly determined by the hematocrit level. This population has chronic high blood viscosity levels, which can be predicted using other blood elements.

Hemorheology: the critical role of flow type in blood viscosity measurements

The crucial role of the hemorheological characteristics of blood in a range of diagnoses, treatments and drug delivery mechanisms is widely accepted. Nonetheless, the literature on blood rheology remains inconclusive and sometimes even contradictory. This is in part due to natural variance of blood samples from one study to another, but also stems from fundamental differences in the consequences of the choice of rheometric flow employed. Here, and using a detailed and accurate computational scheme, we thoroughly study the role of flow type in measurement of blood viscosity. Performing these in silico measurements, we isolate the role of flow type and geometry at different hematocrit levels. We show that flow curves obtained in pressure-driven flows relevant to laminar circulatory flows deviate greatly from ones obtained in drag flow at the same hematocrit level. Our numerical platform also allows for the yield stress to be measured under quiescent conditions and without imposing any flow for different hematocrits. We discuss the scaling of the yield stress with the hematocrit level, and show that the differences in pressure vs. drag flows stem from the Red Blood Cell (RBC) orientation at different flow rates as well as the existence of a cell free layer close to the walls.

Standardization for obtaining blood viscosity: A systematic review

INTRODUCTION

There is evidence to suggest that blood viscosity (BV) is involved in several pathological processes. In this review, we evaluated the different methods of BV acquisition, analyzing the sample storage time, the storage temperature, the acquisition time, the acquisition temperature, sample volume, and shear rates, in order to standardize this technique.

METHODS

We selected 50 articles with methods of obtaining BV, evaluating pathologies through BV, comparing rheological equipment, monitoring, and regulating BV.

RESULTS AND CONCLUSION

Measurements should be obtained as soon as possible, to reduce hemorheological changes. It is necessary to refrigerate them at 4°C when the storage time is long. The acquisition time is related to the equipment used. BV measurements at 37°C will represent the real BV in vivo more faithfully. In order to understand the BV phenomena, the shear rates must be between 0.1 and 1000 s-1. There is a wide variety of equipment available for measuring the BV.