Effect of intracranial pressure on photoplethysmographic waveform in different cerebral perfusion territories: A computational study

• Published in: Frontiers in physiology Vol. 14; p. 1085871
• Main Authors: Liu, Haipeng, Pan, Fan, Lei, Xinyue, Hui, Jiyuan, Gong, Ru, Feng, Junfeng, Zheng, Dingchang
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 16.03.2023
• Subjects: artery network; cerebral microcirculation; computational simulation; intracranial pressure (ICP); photoplethysmography (PPG); Physiology; windkessel effect; artery network; photoplethysmography (PPG); computational simulation; intracranial pressure (ICP); cerebral microcirculation; windkessel effect
• ISSN: 1664-042X; 1664-042X
• DOI: 10.3389/fphys.2023.1085871

Background: 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. Aim: To investigate the effect of ICP changes on the waveform of intracranial PPG signals of different cerebral perfusion territories. Methods: 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). 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. 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. Conclusion: 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.