Sparks Sierra, Hayes Genevieve, Pinto Joana, Bulte Daniel
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, United Kingdom.
Front Physiol. 2024 Aug 8;15:1384113. doi: 10.3389/fphys.2024.1384113. eCollection 2024.
Smooth muscle is integral to multiple autonomic systems, including cerebrovascular dynamics through vascular smooth muscle cells and in ocular muscle dynamics, by regulating pupil size. In the brain, smooth muscle function plays a role in cerebrovascular reactivity (CVR) that describes changes in blood vessel calibre in response to vasoactive stimuli. Similarly, pupil size regulation can be measured using the pupillary light response (PLR), the pupil's reaction to changes in light levels. The primary aim of this study was to explore the interplay between cerebral blood flow and pupil dynamics, evaluated using CVR and PLR, respectively.
A total of 20 healthy adults took part in a CVR gas stimulus protocol and a light and dark flash PLR protocol. CVR was calculated as the blood flow velocity change in the middle cerebral artery, measured using transcranial Doppler ultrasound in response to a 5% increase in CO. Multiple PLR metrics were evaluated with a clinical pupillometer.
CVR and PLR metrics were all within the expected physiological ranges for healthy adults. Nine different PLR metrics, assessed through the light and dark flash protocols, were compared against CVR. A significant negative relationship was observed between the latency of the PLR in the dark flash protocol and CVR. No statistically significant relationships were found between CVR and other PLR metrics.
This is the first study to investigate the relationship between cerebral blood flow and pupil dynamics. A significant relationship between dark flash latency and CVR was observed. Future work includes evaluating these relationships using more robust CVR and PLR measurement techniques in a larger, more diverse cohort. Notably, more research is warranted into the PLR using a dark flash protocol and its connection to cerebrovascular function.
平滑肌是多个自主神经系统不可或缺的一部分，包括通过血管平滑肌细胞参与脑血管动力学，以及通过调节瞳孔大小参与眼部肌肉动力学。在大脑中，平滑肌功能在脑血管反应性（CVR）中发挥作用，CVR描述了血管口径对血管活性刺激的变化。同样，瞳孔大小调节可以通过瞳孔对光反应（PLR）来测量，即瞳孔对光强度变化的反应。本研究的主要目的是探讨分别使用CVR和PLR评估的脑血流与瞳孔动力学之间的相互作用。
共有20名健康成年人参与了CVR气体刺激方案以及明暗闪光PLR方案。CVR通过经颅多普勒超声测量大脑中动脉的血流速度变化来计算，该变化是对CO增加5%的反应。使用临床瞳孔计评估多个PLR指标。
CVR和PLR指标均在健康成年人预期的生理范围内。通过明暗闪光方案评估的9种不同PLR指标与CVR进行了比较。在暗闪光方案中观察到PLR潜伏期与CVR之间存在显著的负相关。在CVR与其他PLR指标之间未发现统计学上的显著关系。
这是第一项研究脑血流与瞳孔动力学之间关系的研究。观察到暗闪光潜伏期与CVR之间存在显著关系。未来的工作包括在更大、更多样化的队列中使用更可靠的CVR和PLR测量技术评估这些关系。值得注意的是，有必要使用暗闪光方案对PLR及其与脑血管功能的联系进行更多研究。
