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This study validated a temple-worn optical wearable device against transcranial Doppler ultrasound, the gold standard for measuring cerebral blood flow velocity, in 20 healthy adults during exercise and postural changes. The wearable's Brain Flow index showed strong correlation with middle cerebral artery blood flow velocity measurements (r = 0.795-0.799), accurately tracking both the direction and timing of cerebral blood flow changes during physical and postural challenges. The device successfully distinguished cerebral blood flow patterns from heart rate changes, demonstrating its potential for continuous cerebral hemodynamic monitoring outside laboratory settings.
Why it matters
Continuous monitoring of brain blood flow has been largely confined to research laboratories due to equipment limitations. A validated wearable device could enable real-time cerebral hemodynamic tracking in clinical settings, during sports, or for individuals at risk of cerebrovascular events, potentially improving diagnosis and management of conditions affecting brain blood flow.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Cerebral hemodynamics are difficult to monitor continuously outside the laboratory. Optical head-worn wearables have been proposed for tracking cerebral blood-flow signals, but they require comparison with an established cerebrovascular reference before they can be interpreted. We evaluated a temple-worn optical wearable, Temple, that outputs a proprietary, dimensionless Brain Flow index, intended as a proxy for relative changes in cerebral hemodynamics, against transcranial Doppler (TCD) ultrasound, which measures blood-flow velocity in the middle cerebral artery (MCAv). Twenty-three healthy adults completed two physiological challenges that elicit distinct and acute cerebral hemodynamic responses: a cycle-ergometer exercise protocol and a stand-to-supine postural transition protocol. Twenty participants were analyzed per protocol. The Brain Flow index tracked MCAv in both protocols, with significant within-subject temporal correlations (median Pearson r = 0.795 and 0.799 for exercise and postural transition; p < 0.001) and directionally concordant, statistically significant transition responses for both increases and decreases in flow. Bland-Altman analysis of the normalized transition responses showed small mean biases between the two devices, consistent with similar relative response shapes. Because both signals were standardized within session before this comparison, it addresses the shape of the relative change rather than agreement in absolute units. The Brain Flow index reproduced the direction and time course of MCAv under both perturbations, including the postural transition, where heart rate moved in the opposite direction. Further studies using complementary modalities and additional cerebrovascular reactivity challenges are required to establish clinical use cases and cerebral specificity of the Brain Flow index.