![]() ![]() The cyclic fluctuations of a PPG signal reflect volumetric changes in the microcirculation, which is regulated by many physiological factors, e.g., respiratory pattern, arterial stiffness, and the mechanical properties of surrounding tissues. The photoplethysmography (PPG) technology has been applied in the daily monitoring of many physiological parameters and may enable non-invasive long-term ICP monitoring. To ease the postoperative ICP monitoring especially in TBI patients, it is essential to develop non-invasive methods of ICP monitoring. ![]() ![]() The insertion of the tube is invasive with a 5%–7% risk of hemorrhage, and is difficult to perform in some patients with inherently small ventricles size ( Harary et al., 2018). In EVD measurement, the ICP is transmitted into an external saline-filled tube through a strain-gauge transducer for pressure measurement. Currently, external ventricular drain (EVD) is considered as the gold standard of ICP monitoring due to its accuracy with additional function of CSF drainage ( Harary et al., 2018). ![]() For decades, ICP monitoring has been a cornerstone of traumatic brain injury (TBI) management ( Stocchetti et al., 2014). ICP can be significantly changed in many neurological diseases ( Czosnyka and Pickard, 2004). ICP is derived from cerebral blood and cerebrospinal fluid (CSF) circulatory dynamics. Intracranial pressure (ICP), defined as the pressure within the craniospinal compartment, is an important physiological parameter that reflects the biomechanical status of the brain. Age and measurement site could also significantly influence intracranial PPG waveform. There were significant effects of age and territory on all waveform features except age on mean.Ĭonclusion: 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). 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. Results: 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. 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). We simulated ICP and PPG signals of three perfusion territories in three ages (20, 40, and 60 years) and four intracranial capacitance conditions (normal, 20% decrease, 50% decrease, and 75% decrease). Methods: Based on lump-parameter Windkessel models, we developed a computational model consisting three interactive parts: cardiocerebral artery network, ICP model, and PPG model. However, it is still unknown if ICP changes can lead to waveform changes in intracranial PPG signals.Īim: To investigate the effect of ICP changes on the waveform of intracranial PPG signals of different cerebral perfusion territories. 3Brain Injury Center, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, Chinaīackground: 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).2College of Electronics and Information Engineering, Sichuan University, Chengdu, China.1Research Centre for Intelligent Healthcare, Coventry University, Coventry, United Kingdom.Haipeng Liu 1 Fan Pan 2 Xinyue Lei 2 Jiyuan Hui 3 Ru Gong 3 Junfeng Feng 3* Dingchang Zheng 1* ![]()
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