New Design Rules Could Make Wearable Heart Monitors Smaller and More Accurate
Researchers have identified the optimal spacing between light sensors and emitters in wearable cardiovascular devices, potentially enabling thinner, cheaper monitors that work reliably on real skin. The findings could accelerate adoption of continuous heart monitoring for clinical care and consumer health tracking.
Originaltitel: Methodology for enhanced optical signal acquisition in wearable cardiovascular monitoring: initial findings
<p>Background: Non-invasive optical measurements such as diffuse correlation spectroscopy and photoplethysmography provide critical physiological information, including cardiovascular parameters. Compact and wearable optical devices enable point-of-care and daily monitoring of cardiovascular signals. Objective: In this study, we propose a comprehensive methodology for informed design of optical transceivers to optimize signal acquisition. Specifically, we investigated the dependence of depth sensitivity on scattering as a function of source-detector distance (SDD). Methods: Speckle variance optical coherence tomography was performed on healthy adult volunteers (3 female, 3 male) to obtain three-dimensional angiograms of the skin microvascular network. Using machine vision algorithms, we quantified microvascular parameters including average depth, width, and volumetric density. These parameters were incorporated into a multi-layer skin digital twin model, and Monte Carlo simulations of light transport at 660 nm were performed across a range of SDD values. By analyzing scattering events in each skin layer, we quantified the SDD-dependent depth sensitivity. Results: Our results indicate that at short SDDs (i.e., 0.15 mm), scattering predominantly occurs in the upper dermis (i.e., 48.8%), whereas at longer SDDs (i.e., 4 mm), the hypodermis becomes dominant (i.e., 40.8%). With an average microvascular depth of 136 +/- 43 mu m (within the upper dermis), we identified an optimal SDD of 0.75 mm, yielding a maximum scattering contribution of 56.5% for the studied population. Conclusion: Our methodology establishes a foundation for patient-specific optimization of optical signal acquisition, with potential applications in diverse populations, including hypertensive elderly patients. Significance: Our study enables patient-specific device design addressing physiological variations across individuals (e.g. differences in microvascular networks and skin tone).</p>