Accurate low shear viscosity assessment in health and disease
- 作者：McMillan ; D. E.
- 刊名：Biorheology
- 出版年：1995
- 期刊代码：37_0006355x
- 类别：med
- 出版时间：March 6, 1995
- 卷：32
- 期：2-3
- 页码：361-362
- 文件大小：142 K
摘要
Clinical hemorheology is the study of the flow properties of blood, but direct assessment of blood flow properties is less common than surrogate assessments-plasma fibrinogen, blood sedimentation, red cell aggregation, plasma viscosity, and total globulin. This indirect evaluation is due to the difficulty in measuring the flow resistance of a freshly obtained thin fluid that is inherently unstable. Rotational viscometers have dominated the few blood studies because blood flow resistance differs so much at high and low shear rates. A commercial cone and plate viscometer used in early clinical studies failed to achieve useful results, leading a committee to recommend that measurements above 100 sec−1 and below 1 sec−1 be made in clinical assessment. No commercial instrument has been reliable enough to dominate blood rheological studies despite this simple recommendation. I have evolved a Couette instrument whose blood geometry was introduced at MIT 30 years ago. It uses an air bearing and guard ring to avoid low shear rate distortion and a stepping motor to facilitate flow onset at a wide variety of shear rates. Automatic operation, mixing and standard flow onset delays at low shear rate contribute to better low shear rate reproducibility. Blood can be studied with or without hematocrit adjustment, with different gap sizes, and with correction for non-Newtonian behavior. Blood can be studied over a shear rate range from 360 to .03 sec−1 in 15 minutes. This instrument can also determine onset of high shear rate flow instability and study viscoelastic and thixotropic behavior during the same study. The variation of one individual over months/years is one third the general variation, making blood viscosity assessment a better index of individual behavior than its surrogates.