Catharina Hospital, Eindhoven, The Netherlands.
Physiol Meas. 2020 Aug 11;41(7):075006. doi: 10.1088/1361-6579/ab979d.
Quantifying the absolute coronary blood flow can be done using continuous infusion thermodilution requiring a dedicated infusion catheter. Up to now, there has been little insight into the effect of small variabilities in the physical parameters on the temperature gradient along this catheter. The key goal of this study is to develop and validate a computer model that predicts the temperature of the infusion fluid at the infusion site of the infusion catheter. A secondary goal is to gain insight into the influence of physical variations for the individual patient on the calculated blood flow rate.
A numerical model of the temperature in the catheter was built using the convection-diffusion equation and validated using an in vitro setup. A sensitivity analysis was performed to investigate the influence of the catheter path inside the body and the temperature of the infusion fluid at different infusion rates. These results were compared to in vivo measurements of 94 patients. Finally, the variation in the computed blood flow rate is estimated considering an average patient, using small variations in the physical parameters.
The computed temperature corresponded well with the in vitro measurements, since a maximal difference of 1.5% was observed. The length of the catheter path inside the body had the most influence on the temperature of the infusion fluid at the infusion site. Moreover, temperatures from the numerical model were similar to the results from in vivo measurements. By varying the length of the catheters with 0.04 m, the largest deviation in the calculated blood flow was 33.3 ml/min.
Insight is gained into the influence of physical variations on the temperature of the infusion fluid at the infusion site of the catheter using thermodilution. The developed numerical model can possibly be used to reduce time in estimating the blood flow rate.
使用连续输注热稀释法可以定量测量绝对冠状动脉血流量，该方法需要专用的输注导管。到目前为止，对于物理参数的小变化对沿导管的温度梯度的影响，人们了解甚少。本研究的主要目标是开发和验证一种计算机模型，该模型可以预测输注导管输注部位的输注液的温度。次要目标是深入了解个体患者的物理变化对计算血流量的影响。
使用对流-扩散方程建立导管内温度的数值模型，并使用体外装置进行验证。进行了敏感性分析，以研究导管在体内的路径以及不同输注率下输注液温度对计算血流量的影响。将这些结果与 94 名患者的体内测量结果进行了比较。最后，考虑到平均患者，使用物理参数的微小变化来估计计算出的血流量变化。
计算出的温度与体外测量结果非常吻合，因为观察到最大差异为 1.5%。导管在体内的路径长度对输注部位输注液的温度影响最大。此外，数值模型的温度与体内测量结果相似。通过将导管长度变化 0.04 m，计算出的血流量最大偏差为 33.3 ml/min。
通过热稀释法了解了物理变化对导管输注部位输注液温度的影响。开发的数值模型可用于减少估计血流量的时间。
