The aim of this study was to evaluate the analytical performance of a curved capillary configurations on a U-tube structure used in a tabletop fully automated blood viscometer. Precision was assessed using normal and abnormal quality control materials measured repeatedly over 20 days across shear rates of 1–1000 s⁻1. Correlation between straight and curved capillary configurations was evaluated. Sample stability was also assessed at shear rates of 1 s⁻1 and 300 s⁻1 over three consecutive days. The curved capillary system demonstrated robust precision, with total coefficients of variation decreasing with increasing shear rate. Strong correlations were observed between straight and curved capillary measurements across all shear rates. Passing– Bablok regression showed slopes close to unity and intercepts near zero, while Bland–Altman analysis revealed minimal bias without shear-dependent trends. Whole blood viscosity remained stable over three days at both low and high shear rates (all p > 0.98). The curved capillary–based U-tube configuration provides analytically equivalent and stable whole blood viscosity measurements compared with conventional straight capillary systems, supporting its suitability for fully automated blood viscometer.

This research explores the mechanical behavior of whole blood as a shear-thinning fluid and examines yield stress as a crucial parameter for evaluating flow properties in the microvasculature. While previous studies have primarily focused on whole blood viscosity (WBV), this study presents an engineering-based approach to quantitatively evaluate the yield stress of non-Newtonian whole blood using a U-shaped capillary tube. A custom-designed scanning capillary tube, incorporating a biocompatible U-shaped capillary channel, was employed to determine whole blood viscosity (WBV) across shear rates from 1 to 1,000 s⁻1. Yield stress was estimated by extrapolating the shear stress-shear rate relationship using a non-Newtonian shear-thinning flow model. The analysis revealed a strong cubic correlation between hematocrit and yield stress, suggesting an increased risk of flow impairment in the microvasculature with elevated hematocrit levels. This work emphasizes the critical influence of yield stress in regulating microvascular blood flow, particularly under low-shear conditions.

이 연구는 최대근력형과 근지구력형 저항운동이 총운동량과 혈액점도 및 적혈구용적률에 미치는 영향을 조사하고자 하였다. 연구대상자는 저항운동 경력 12개월 이상의 20대 남성 15명으로 선정하였으며, 실험 전 벤치프레스 1RM을 측정하였으며, 조건 별 실험은 1주일간의 간격을 두고 교차배분하여 6세트 씩 최대반복수행 하였다. 그 결과 총운동량은 근지구력강도가 최대근력강도에 비해 높게 나타났으며 (p<.001), 혈액점도와 적혈구용적률은 총운동량에 관계없이 운동 전보다 운동 후에 높아졌다(p<.01). 종합 하면 혈액점도는 운동강도와 운동량에 영향을 받지 않으며, 일회성 저항운동으로 증가한다는 것을 알 수 있었다. 이는 저항운동 프로그램을 구성하는데 있어 임상적으로 의의가 있으며 혈관질환에 관련된 임상환 자들의 운동프로그램을 작성하는데 있어 참고자료가 될 수 있을 것으로 판단된다.

The present study investigated the blood flow at microvascular network. The role of the blood viscosity and the yield stress of blood on the flow at the microvascular network was examined to find the condition of hemostasis. When the yield stress was less than 0.005Pa, there was no stagnant region in the capillary network used in the study. However, when the yield stress increased to 0.05Pa, stagnant areas began to appear, which grew and expanded rapidly with further increase in the yield stress. From the blood viscosity profile of a patient, one can estimate the yield stress of blood, from which the risk of hemostasis can be determined.