Noninvasive, wearable device feasible for determining stroke risk

Key takeaways:

• Participants underwent a breath-holding exercise and imaging of blood flow.
• The high-risk stroke group had a higher increase of blood volume; the lower-risk group had greater increase in blood flow rate.

Noninvasive speckle contrast optical spectroscopy may be a feasible method for determining whether individuals are at high or low risk for stroke, according to a study published in Biomedical Optics Express.

“If we can build a brain stress test equivalent that is scalable, affordable and noninvasive, that would make a massive contribution to public health,” Charles Liu, MD, PhD, co-senior study author and professor of clinical neurological surgery at the Keck School of Medicine at the University of Southern California, said in a related release.

Liu and colleagues sought to advance a novel, noninvasive method to assess stroke risk through speckle contrast optical spectroscopy (SCOS), which monitors regional changes in blood flow and volume of the brain during breath holding.

Their proof-of-concept study recruited participants from the California Institute of Technology as well as the greater Los Angeles area, including 53 adults who were comfortable with breath holding and without major respiratory disease. All participants were required to wear a noninvasive SCOS device, which utilized a single-mode continuous wave laser diode able to deliver up to 200 megawatts (mW) of current.

The final analysis included 160 breath-holding events logged by 50 individuals, divided into two equal low- and high-risk groups, whose evaluations were made via the Cleveland Clinic Stroke Risk Calculator. The high-risk group was further divided into subgroups based on scores.

Prior to treatment, all participants were required to complete a health-related questionnaire and had their blood pressure taken. During treatment, the device was placed on the forehead, 5 mm from the skin, with illumination power set to 45mW and a camera taking pictures at 60 frames per second with recording of blood cells as they flow through the brain in 12-bit images. Total time for the procedure, where the individual was asked to remain still and to avoid head movement, was 180 seconds: 60 seconds of normal breathing, then voluntary breath holding for a time determined by the comfort of the participant, then recovery followed by normal respiration.

According to the results, individuals from the high-risk cohort demonstrated a greater increase in brain blood volume and lower increase of blood flow (P = 0.014) when holding their breath compared with the low-risk group.

Additionally, Liu and colleagues reported a statistically significant difference between groups when comparing blood flow or blood volume change, with those deemed low risk showing a higher increase of brain volume and those deemed high risk showing greater increase in rate of blood flow.

“Due to the portability and cost-effectiveness of the compact SCOS device, we would like to underscore the potential of deploying the device and incorporating the breath-holding maneuver in various geographical settings,” Liu and colleagues wrote.

Editor's Note: This article was updated on Oct. 29, 2024 to adjust language in the key takeaways section regarding high-risk and low-risk stroke groups.

Reference:

USC-Caltech team tests new noninvasive tool to predict stroke risk. https://keck.usc.edu/news/usc-caltech-team-tests-new-noninvasive-tool-to-predict-stroke-risk/. Published Sept. 30, 2024. Accessed Oct. 4, 2024.