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Critical Stress of Blood

  Cell Deformability
  Cell Aggregation
  Blood Critical Stress
  Disposable Kit / Chip
Blood Viscosity_1
Blood viscosity
A physical index to represent stickiness of blood.
The higher viscosity, the less fluidity becomes and the more pumping
power is required.

Elevated blood viscosity, which is known for the direct cause of
cardiovascular diseases, is caused by hyper-aggregation of RBCs,
degradation of cell deformability, and increased plasma viscosity.

Blood viscosity, however, is very difficult to measure and describe a
single number due to its shear-rate dependent viscosity.

Critical Stress of Blood
Critical stress of blood, which is defined as a minimum shear stress
to required to disperse aggregated RBCs, can be a new index to repr
esent the viscosity of whole blood.

1. Features
An innovative method with disposable microchip can measure critical
shear stress at clinical environment

- optimal design considering Farhaeus
-Lindqvist effect
- short test time & easy measurement
- disposable test kit

2. Specifications
Index CS (critical stress)
CT (critical time)

Sample volume 8 ul
Method Light backscattering
Instrument RSAnD-300, RSD-300
Disposable RSD-K03 (micro-capillary)

3. Measurement principles
Cell Aggregation_2
4. Validation & Comparison
A) Hematocrit-independence
Critical stress is proven to be independent of hematocrit (J. Biomechanics, 2009). Conventional aggregation
measurement requires laboratory adjustment of hematocrit. However, the present measurement with RheoScan
system does not require hematocrit adjustment.
B) Couette flow vs. Poiseullie flow
This difference is attributed to a lower effectiveness of the shear stress, which direction is parallel to the rouleau
x interface if alignment with the rouleaux interface is lacking.

S. Chien et al, Microvasc. Res. 13 (1977), 327_333
H. Lim et al, J. Biomechanics, 43 (2009), 546_550