Murphy Liam, Chase J Geoffrey
Department of Mechanical Engineering, University of Canterbury, 20 Kirkwood Avenue, Christchurch, New Zealand.
Department of Mechanical Engineering, University of Canterbury, 20 Kirkwood Avenue, Christchurch, New Zealand.
Comput Methods Programs Biomed. 2023 Feb;229:107254. doi: 10.1016/j.cmpb.2022.107254. Epub 2022 Nov 24.
Central blood pressure (BP) better reflects the loading conditions on the major organs and is more closely correlated with future cardiovascular events. The increased invasiveness and risk of infection prevents the routine measurement of central BP. Arterial transfer functions can provide central BP estimates from clinically available peripheral measurements. However, current methods are either generalized, potentially lacking the ability to adapt to inter and intra subject variability, or individualized based on additional, clinically unavailable, pulse transit time measurements. This work proposes a novel, self-contained method for individualizing an arterial transfer function from a single peripheral pressure measurement, capable of accurately estimating central BP in a range of hemodynamic conditions.
Pulse wave analysis of femoral BP waves was employed to formulate initial approximations of central BP and arterial inlet flow waveforms, to serve as objective functions for the identification of all model parameters. Root mean squared error (RMSE), and systolic and pulse pressure errors were assessed with respect to invasive aortic BP measurements in a seven (7) porcine endotoxin experiments. Systolic and pulse pressure errors were analysed using Bland-Altman analysis. Method accuracy is also compared with an idealized transfer function, derived using the measured aortic-femoral pulse transit time and minimizing the RMSE of model output pressure with respect to reference aortic pressure, a generalized transfer function model, and invasive femoral pressure measurements.
Mean bias and limits of agreement (95% CI) for the proposed method were 1.0(-4.6, 6.7)mmHg and -1.0(-6.6, 4.6)mmHg for systolic and pulse pressure, respectively, compared to 3.6(-0.9, 8.2)mmHg and 2.7(-1.8, 7.3)mmHg for the generalized transfer function model. Mean bias and limits of agreement for femoral pressure measurements were -6.4(-15.0, 2.3)mmHg and -9.4(-18.1, -0.8)mmHg, for systolic and pulse pressure, respectively. The pooled mean and standard deviation of the RMSE produced by the single measurement method, relative to reference aortic pressure, was 4.3(1.1)mmHg, consistent with estimates produced by the idealized transfer function, 3.9(1.2)mmHg, and improving of the generalized transfer function, 4.6(1.4)mmHg.
The proposed single measurement method provides accurate central BP estimates from routinely available peripheral pressure measurements, and nothing else. The method allows for the individualization of transfer functions on a per patient basis to better capture changes in patient condition during the progression of disease and subsequent treatment, at no additional clinical cost.
中心血压能更好地反映主要器官的负荷情况，且与未来心血管事件的相关性更强。中心血压测量的侵入性增加及感染风险阻碍了其常规测量。动脉传递函数可根据临床上可获取的外周测量值估算中心血压。然而，当前方法要么是通用的，可能缺乏适应个体间和个体内差异的能力，要么是基于额外的、临床上无法获取的脉搏传输时间测量进行个体化。本研究提出一种新颖的、独立的方法，可根据单次外周压力测量对动脉传递函数进行个体化，能够在一系列血流动力学条件下准确估算中心血压。
采用股动脉血压波的脉搏波分析来制定中心血压和动脉入口血流波形的初始近似值，作为识别所有模型参数的目标函数。在七（7）项猪内毒素实验中，相对于有创主动脉血压测量值，评估均方根误差（RMSE）以及收缩压和脉压误差。使用布兰德-奥特曼分析对收缩压和脉压误差进行分析。还将该方法的准确性与理想化传递函数、通用传递函数模型以及有创股动脉压力测量进行比较，理想化传递函数是利用测量的主动脉-股动脉脉搏传输时间并使模型输出压力相对于参考主动脉压力的RMSE最小化而得出的。
与通用传递函数模型相比，所提方法的收缩压和脉压的平均偏差及一致性界限（95%CI）分别为1.0（-4.6，6.7）mmHg和-1.0（-6.6，4.6）mmHg，而通用传递函数模型分别为3.6（-0.9，8.2）mmHg和2.7（-1.8，7.3）mmHg。股动脉压力测量的收缩压和脉压的平均偏差及一致性界限分别为-6.4（-15.0，2.3）mmHg和-9.4（-18.1，-0.8）mmHg。相对于参考主动脉压力，单次测量方法产生的RMSE的合并均值和标准差为4.3（1.1）mmHg，与理想化传递函数产生的估计值3.9（1.2）mmHg一致，且优于通用传递函数的4.6（1.4）mmHg。
所提的单次测量方法仅根据常规可获取的外周压力测量就能准确估算中心血压。该方法允许在个体患者基础上对传递函数进行个体化，以更好地捕捉疾病进展和后续治疗过程中患者病情的变化，且无需额外的临床成本。
