Diffuse optical assessment of cerebral‐autoregulation in older adults stratified by cerebrovascular risk

• Published in: Journal of biophotonics 2020-10, Vol.13 (10), p.e202000073-n/a
• Main Authors: Bahrani, Ahmed A., Kong, Weikai, Shang, Yu, Huang, Chong, Smith, Charles D., Powell, David K., Jiang, Yang, Rayapati, Abner O., Jicha, Gregory A., Yu, Guoqiang
• Format: Article
• Language: English
• Subjects: Adults; Aged; Biomarkers; Blood flow; Blood Pressure; Cerebral blood flow; cerebral blood oxygenation; cerebral‐autoregulation; Cerebrovascular Circulation; cerebrovascular disease; Cerebrovascular diseases; Complications; diffuse correlation spectroscopy; head‐up‐tilting; Health risks; Heart diseases; Hemoglobin; Homeostasis; Humans; Infrared instruments; low‐frequency oscillation; Microvasculature; Microvessels; near‐infrared spectroscopy; Older people; Optical instruments; Oscillations; Risk; Risk Assessment; Spectroscopy, Near-Infrared; Transfer functions
• ISSN: 1864-063X; 1864-0648
• DOI: 10.1002/jbio.202000073

Diagnosis of cerebrovascular disease (CVD) at early stages is essential for preventing sequential complications. CVD is often associated with abnormal cerebral microvasculature, which may impact cerebral‐autoregulation (CA). A novel hybrid near‐infrared diffuse optical instrument and a finger plethysmograph were used to simultaneously detect low‐frequency oscillations (LFOs) of cerebral blood flow (CBF), oxy‐hemoglobin concentration ([HbO2]), deoxy‐hemoglobin concentration ([Hb]) and mean arterial pressure (MAP) in older adults before, during and after 70° head‐up‐tilting (HUT). The participants with valid data were divided based on Framingham risk score (FRS, 1‐30 points) into low‐risk (FRS ≤15, n = 13) and high‐risk (FRS >15, n = 11) groups for developing CVD. The LFO gains were determined by transfer function analyses with MAP as the input, and CBF, [HbO2] and [Hb] as the outputs (CA ∝ 1/Gain). At resting‐baseline, LFO gains in the high‐risk group were relatively lower compared to the low‐risk group. The lower baseline gains in the high‐risk group may attribute to compensatory mechanisms to maintain stronger steady‐state CAs. However, HUT resulted in smaller gain reductions in the high‐risk group compared to the low‐risk group, suggesting weaker dynamic CAs. LFO gains are potentially valuable biomarkers for early detection of CVD based on associations with CAs. A hybrid diffuse optical instrument was used to simultaneously detect lowfrequency oscillation (LFO) signals of cerebral blood flow and oxygenation in older adults at low‐risk or high‐risk for developing cerebrovascular disease (CVD). Compared to the low‐risk group, the high‐risk group demonstrated higher LFO gains at resting baseline but smaller gain reductions during head‐up‐tilting. LFO gain, correlating inversely with cerebral autoregulation capability, is a potential biomarker for early detection of CVD.