title: A Novel Blood Viscosity Estimation Method Based on Pressure-Flow Characteristics of an Oxygenator During Cardiopulmonary Bypass.
abstract: During cardiopulmonary bypass (CPB), blood viscosity conspicuously increases and decreases due to changes in hematocrit and blood temperature. Nevertheless, blood viscosity is typically not evaluated, because there is no technology that can provide simple, continuous, noncontact monitoring. We modeled the pressure-flow characteristics of an oxygenator in a previous study, and in that study we quantified the influence of viscosity on oxygenator function. The pressure-flow monitoring information in the oxygenator is derived from our model and enables the estimation of viscosity. The viscosity estimation method was proposed and investigated in an in vitro experiment. Three samples of whole bovine blood with different hematocrit levels (21.8, 31.0, and 39.8%) were prepared and perfused into the oxygenator. As the temperature changed from 37°C to 27°C, the mean inlet pressure (Pin) and outlet pressure (Pout) of the oxygenator and the flow (Q) and viscosity of the blood were measured. The estimated viscosity was calculated from the pressure gradient (ΔP = Pin- Pout) and Q and was compared to the measured blood viscosity. A strong correlation was found between the two methods for all samples. Bland-Altman analysis revealed a mean bias of -0.0263 mPa.s, a standard deviation of 0.071 mPa.s, limits of agreement of -0.114-0.166 mPa.s, and a percent error of 5%. Therefore, this method is considered compatible with the torsional oscillation viscometer that has plus or minus 5% measurement accuracy. Our study offers the possibility of continuously estimating blood viscosity during CPB.
authors: Department of Medical Engineering, Faculty of Health Siences, Junshin Gakuen University.
authors: Shigeyuki
authors: S
authors: Okahara
authors: Department of System Cybernetics, Institute of Engineering, Hiroshima University.
authors: Zu
authors: Z
authors: Soh
authors: Department of Clinical Engineering, Hiroshima University Hospital.
authors: Satoshi
authors: S
authors: Miyamoto
authors: Department of Clinical Engineering, Hiroshima University Hospital.
authors: Hidenobu
authors: H
authors: Takahashi
authors: Department of Medical Engineering, Faculty of Health Siences, Junshin Gakuen University.
authors: Hideshi
authors: H
authors: Itoh
authors: Department of Cardiovascular Surgery, Hiroshima University Hospital.
authors: Shinya
authors: S
authors: Takahashi
authors: Department of Cardiovascular Surgery, Hiroshima University Hospital.
authors: Taijiro
authors: T
authors: Sueda
authors: Department of System Cybernetics, Institute of Engineering, Hiroshima University.
authors: Toshio
authors: T
authors: Tsuji
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001809:Blood Viscosity; D002315:Cardiopulmonary Bypass / Q000295:instrumentation*; D002417:Cattle; D006400:Hematocrit; D008955:Models, Cardiovascular; D010106:Oxygenators; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013696:Temperature; D013997:Time Factors
keywords: Blood viscosity; Cardiopulmonary bypass; Oxygenator; Pressure gradient