Background and Objectives: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.

Methods: 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.

Results: 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.

Conclusion: 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.

背景与目的：中风量（SV）和心输出量（CO）是危重患者血液动力学管理的重要指标。连续监测这些指标的临床可用设备是侵入性的，在血液动力学不稳定期间，侵入性较小的方法的性能较差。脉搏波速度（PWV）通过提供有关血管紧张度变化的信息，可能会改善SV和CO的估计。本研究调查了使用PWV进行基于模型的脉冲轮廓分析方法的参数识别是否会提高SV估计的准确性。

方法：比较了三元素风帆脉搏轮廓分析模型的三种实现：常量Z，水锤和Bramwell-Hill方法。每种实现方式都以不同方式标识特征阻抗参数（Z）。第一种方法识别Ž静态，并且不使用PWV和后两种方法使用PWV来动态更新ž。在一项动物试验中测试了SV估计的准确性，该试验在5只猪中诱发了严重的血液动力学变化。将模型预测的SV与使用主动脉流量探针测得的SV进行比较。

结果： SV百分比误差具有中位数偏差和[（IQR）；（2.5、97.5％）--0.5％[（-6.1％，4.7％）；（-50.3％，+24.1％）]（对于常数Z方法）为0.6％[（-4.9％，6.2％）；（-43.4％，+ 29.3％）]用于水锤法，以及0.8％[（-6.5，8.6）; （-37.1％，+ 47.6％）]。

结论：与常量Z方法相比，通过Bramwell-Hill方程或水锤方程将PWV用于动态Z参数识别并不能显着改善3元素风帆脉搏轮廓分析模型对血液动力学变化期间SV的预测。