Smith Rachel, Balmer Joel, Pretty Christopher G, Mehta-Wilson Tashana, Desaive Thomas, Shaw Geoffrey M, Chase J Geoffrey
Department of Mechanical Engineering, University of Canterbury, New Zealand.
Department of Mechanical Engineering, University of Canterbury, New Zealand.
Comput Methods Programs Biomed. 2020 Oct;195:105553. doi: 10.1016/j.cmpb.2020.105553. Epub 2020 May 26.
Stroke volume (SV) and cardiac output (CO) are important metrics for hemodynamic management of critically ill patients. Clinically available devices to continuously monitor these metrics are invasive, and less invasive methods perform poorly during hemodynamic instability. Pulse wave velocity (PWV) could potentially improve estimation of SV and CO by providing information on changing vascular tone. This study investigates whether using PWV for parameter identification of a model-based pulse contour analysis method improves SV estimation accuracy.
Three implementations of a 3-element windkessel pulse contour analysis model are compared: constant-Z, water hammer, and Bramwell-Hill methods. Each implementation identifies the characteristic impedance parameter (Z) differently. The first method identifies Z statically and does not use PWV, and the latter two methods use PWV to dynamically update Z. Accuracy of SV estimation is tested in an animal trial, where interventions induce severe hemodynamic changes in 5 pigs. Model-predicted SV is compared to SV measured using an aortic flow probe.
SV percentage error had median bias and [(IQR); (2.5th, 97.5th percentiles)] of -0.5% [(-6.1%, 4.7%); (-50.3%, +24.1%)] for the constant-Z method, 0.6% [(-4.9%, 6.2%); (-43.4%, +29.3%)] for the water hammer method, and 0.8% [(-6.5, 8.6); (-37.1%, +47.6%)] for the Bramwell-Hill method.
Incorporating PWV for dynamic Z parameter identification through either the Bramwell-Hill equation or the water hammer equation does not appreciably improve the 3-element windkessel pulse contour analysis model's prediction of SV during hemodynamic changes compared to the constant-Z method.
每搏输出量（SV）和心输出量（CO）是危重症患者血流动力学管理的重要指标。临床上用于连续监测这些指标的现有设备具有侵入性，而侵入性较小的方法在血流动力学不稳定时表现不佳。脉搏波速度（PWV）可能通过提供血管张力变化的信息来改善SV和CO的估计。本研究调查使用PWV进行基于模型的脉搏轮廓分析方法的参数识别是否能提高SV估计的准确性。
比较了三元件风箱式脉搏轮廓分析模型的三种实现方式：恒Z法、水击法和布拉姆韦尔 - 希尔法。每种实现方式识别特征阻抗参数（Z）的方式不同。第一种方法静态识别Z且不使用PWV，后两种方法使用PWV动态更新Z。在一项动物试验中测试SV估计的准确性，在5头猪中进行干预以诱导严重的血流动力学变化。将模型预测的SV与使用主动脉流量探头测量的SV进行比较。
恒Z法的SV百分比误差的中位数偏差和[（四分位间距）；（第2.5百分位数，第97.5百分位数）]为 -0.5% [（-6.1%，4.7%）；（-50.3%，+24.1%）]，水击法为0.6% [（-4.9%，6.2%）；（-43.4%，+29.3%）]，布拉姆韦尔 - 希尔法为0.8% [（-6.5，8.6）；（-37.1%，+47.6%）]。
与恒Z法相比，通过布拉姆韦尔 - 希尔方程或水击方程纳入PWV进行动态Z参数识别，在血流动力学变化期间并不能明显改善三元件风箱式脉搏轮廓分析模型对SV的预测。
