Michigan State University, East Lansing, Michigan 48824-1226, USA.
Am J Physiol Heart Circ Physiol. 2011 Oct;301(4):H1389-95. doi: 10.1152/ajpheart.00443.2011. Epub 2011 Jul 29.
We investigated the system identification approach for potentially improved estimation of pulse transit time (PTT), a popular arterial stiffness marker. In this approach, proximal and distal arterial waveforms are measured and respectively regarded as the input and output of a system. Next, the system impulse response is identified from all samples of the measured input and output. Finally, the time delay of the impulse response is detected as the PTT estimate. Unlike conventional foot-to-foot detection techniques, this approach is designed to provide an artifact robust estimate of the true PTT in the absence of wave reflection. The approach is also applicable to arbitrary types of arterial waveforms. We specifically applied a parametric system identification technique to noninvasive impedance cardiography (ICG) and peripheral arterial blood pressure waveforms from 15 humans subjected to lower-body negative pressure. We assessed the technique through the correlation coefficient (r) between its 1/PTT estimates and measured diastolic pressure (DP) per subject and the root mean squared error (RMSE) of the DP predicted from these estimates and measured DP. The technique achieved average r and RMSE values of 0.81 ± 0.16 and 4.3 ± 1.3 mmHg. For comparison, the corresponding values were 0.59 ± 0.37 (P < 0.05) and 5.9 ± 2.5 (P < 0.01) mmHg for the conventional technique applied to the same waveforms and 0.28 ± 0.40 (P < 0.001) and 7.2 ± 1.8 (P < 0.001) mmHg for the conventional technique with the ECG waveform substituted for the ICG waveform. These results demonstrate, perhaps for the first time, that the system identification approach can indeed improve PTT estimation.
我们研究了一种潜在的改进脉搏波传导时间（PTT）估计的系统辨识方法，PTT 是一种流行的动脉僵硬度标志物。在这种方法中，近端和远端动脉波形被测量，并分别作为系统的输入和输出。接下来，从测量的输入和输出的所有样本中识别系统脉冲响应。最后，检测脉冲响应的时间延迟作为 PTT 估计。与传统的足部到足部检测技术不同，该方法旨在在没有波反射的情况下，为真正的 PTT 提供一种抗伪影的稳健估计。该方法也适用于任意类型的动脉波形。我们特别将参数系统辨识技术应用于 15 名接受下体负压的人类的非侵入性阻抗心动图（ICG）和外周动脉血压波形。我们通过该技术的 1/PTT 估计值与每个受试者的测量舒张压（DP）之间的相关系数（r）以及从这些估计值和测量 DP 预测的 DP 的均方根误差（RMSE）来评估该技术。该技术的平均 r 和 RMSE 值分别为 0.81 ± 0.16 和 4.3 ± 1.3 mmHg。相比之下，对于应用于相同波形的传统技术，相应的值分别为 0.59 ± 0.37（P < 0.05）和 5.9 ± 2.5（P < 0.01）mmHg，而对于 ECG 波形替代 ICG 波形的传统技术，相应的值分别为 0.28 ± 0.40（P < 0.001）和 7.2 ± 1.8（P < 0.001）mmHg。这些结果表明，系统辨识方法确实可以改善 PTT 估计，这或许是首次证明。
