Control of the Fluid Viscosity in a Mock Circulation
Control of the Fluid Viscosity in a Mock Circulation
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DOI：
10.1111/aor.12948
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发表时间：
2018-01-01
影响因子：
2.4
通讯作者：
Daners, Marianne Schmid
中科院分区：
文献类型：
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作者：
Boes, Stefan;Ochsner, Gregor;Daners, Marianne Schmid
模拟循环允许心室辅助装置的体外研究、开发和测试。甘油水溶液通常用于模拟血液的粘度。由于蒸发和温度变化，溶液的粘度从其初始值漂移，因此基本上偏离血液的目标粘度。此外，当模拟不同的血细胞比容时，需要更换溶液以考虑粘度的变化。本文介绍了一种在模拟循环中控制粘度的方法。该方法利用甘油水溶液的温度和粘度之间的关系，并采用流体粘度的自动控制。为此，现有的模拟循环扩展了工业粘度计，温度探头和加热喷嘴带。用不同的流体粘度得到的结果表明，粘度控制器是至关重要的模拟循环的可重复的实验条件。在甘油水溶液的混合比为49质量%的情况下，控制器可以模拟对应于在30-42摄氏度的温度范围内的29 - 42%的血细胞比容的粘度范围。控制响应没有过冲，对于0.3 cP的粘度阶跃，稳定时间为8.4 min，相当于3.6%的血细胞比容阶跃。在不同粘度下测试了临床使用的两种旋转血泵。在5 L/min的流速下，对于高转子速度，两者都显示出电机电流的大约15%和10%的偏差。不同粘度对测量的水头压力的影响可以忽略不计。因此，模拟循环的粘度控制对于评估心室辅助装置所需的电机电流起着重要作用。对于旋转式血泵功耗的研究和以电机电流为模型输入的流量估算器的开发，集成粘度控制器对准确的测试环境做出了宝贵的贡献。
A mock circulation allows the in vitro investigation, development, and testing of ventricular assist devices. An aqueous-glycerol solution is commonly used to mimic the viscosity of blood. Due to evaporation and temperature changes, the viscosity of the solution drifts from its initial value and therefore, deviates substantially from the targeted viscosity of blood. Additionally, the solution needs to be exchanged to account for changing viscosities when mimicking different hematocrits. This article presents a method to control the viscosity in a mock circulation. This method makes use of the relationship between temperature and viscosity of aqueous-glycerol solutions and employs the automatic control of the viscosity of the fluid. To that end, an existing mock circulation was extended with an industrial viscometer, temperature probes, and a heating nozzle band. The results obtained with different fluid viscosities show that a viscosity controller is vital for repeatable experimental conditions on mock circulations. With a mixture ratio of 49 mass percent of aqueous-glycerol solution, the controller can mimic a viscosity range corresponding to a hematocrit between 29 and 42% in a temperature range of 30-42 degrees C. The control response has no overshoot and the settling time is 8.4 min for a viscosity step of 0.3 cP, equivalent to a hematocrit step of 3.6%. Two rotary blood pumps that are in clinical use are tested at different viscosities. At a flow rate of 5 L/min, both show a deviation of roughly 15 and 10% in motor current for high rotor speeds. The influence of different viscosities on the measured head pressure is negligible. Viscosity control for a mock circulation thus plays an important role for assessing the required motor current of ventricular assist devices. For the investigation of the power consumption of rotary blood pumps and the development of flow estimators where the motor current is a model input, an integrated viscosity controller is a valuable contribution to an accurate testing environment.