Liu Haipeng, Pan Fan, Lei Xinyue, Hui Jiyuan, Gong Ru, Feng Junfeng, Zheng Dingchang
Research Centre for Intelligent Healthcare, Coventry University, Coventry, United Kingdom.
College of Electronics and Information Engineering, Sichuan University, Chengdu, China.
Front Physiol. 2023 Mar 16;14:1085871. doi: 10.3389/fphys.2023.1085871. eCollection 2023.
Intracranial photoplethysmography (PPG) signals can be measured from extracranial sites using wearable sensors and may enable long-term non-invasive monitoring of intracranial pressure (ICP). However, it is still unknown if ICP changes can lead to waveform changes in intracranial PPG signals. To investigate the effect of ICP changes on the waveform of intracranial PPG signals of different cerebral perfusion territories. Based on lump-parameter Windkessel models, we developed a computational model consisting three interactive parts: cardiocerebral artery network, ICP model, and PPG model. We simulated ICP and PPG signals of three perfusion territories [anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA), all left side] in three ages (20, 40, and 60 years) and four intracranial capacitance conditions (normal, 20% decrease, 50% decrease, and 75% decrease). We calculated following PPG waveform features: maximum, minimum, mean, amplitude, min-to-max time, pulsatility index (PI), resistive index (RI), and max-to-mean ratio (MMR). The simulated mean ICPs in normal condition were in the normal range (8.87-11.35 mm Hg), with larger PPG fluctuations in older subject and ACA/PCA territories. When intracranial capacitance decreased, the mean ICP increased above normal threshold (>20 mm Hg), with significant decreases in maximum, minimum, and mean; a minor decrease in amplitude; and no consistent change in min-to-max time, PI, RI, or MMR (maximal relative difference less than 2%) for PPG signals of all perfusion territories. There were significant effects of age and territory on all waveform features except age on mean. ICP values could significantly change the value-relevant (maximum, minimum, and amplitude) waveform features of PPG signals measured from different cerebral perfusion territories, with negligible effect on shape-relevant features (min-to-max time, PI, RI, and MMR). Age and measurement site could also significantly influence intracranial PPG waveform.
颅内光电容积脉搏波描记法（PPG）信号可使用可穿戴传感器从颅外部位进行测量，这可能实现对颅内压（ICP）的长期无创监测。然而，ICP变化是否会导致颅内PPG信号的波形变化仍不清楚。为了研究ICP变化对不同脑灌注区域颅内PPG信号波形的影响。基于集总参数Windkessel模型，我们开发了一个由三个相互作用部分组成的计算模型：心脑动脉网络、ICP模型和PPG模型。我们模拟了三个年龄（20岁、40岁和60岁）和四种颅内电容条件（正常、降低20%、降低50%和降低75%）下三个灌注区域[大脑前动脉、大脑中动脉和大脑后动脉（ACA、MCA和PCA），均为左侧]的ICP和PPG信号。我们计算了以下PPG波形特征：最大值、最小值、平均值、振幅、最小到最大时间、搏动指数（PI）、阻力指数（RI）和最大到平均比值（MMR）。正常条件下模拟的平均ICP在正常范围内（8.87 - 11.35 mmHg），老年受试者以及ACA/PCA区域的PPG波动更大。当颅内电容降低时，平均ICP升高至正常阈值以上（>20 mmHg），最大值、最小值和平均值显著降低；振幅略有降低；所有灌注区域的PPG信号在最小到最大时间、PI、RI或MMR方面没有一致变化（最大相对差异小于2%）。除年龄对平均值的影响外，年龄和区域对所有波形特征均有显著影响。ICP值可显著改变从不同脑灌注区域测量的PPG信号的与值相关（最大值、最小值和振幅）的波形特征，而对与形状相关的特征（最小到最大时间、PI、RI和MMR）影响可忽略不计。年龄和测量部位也可显著影响颅内PPG波形。
