Listen to your heart

Many smartwatches are equipped with health monitors that measure light absorption and reflection in blood vessels to track pulse an oxygen saturation. However, the wrist may not be the ideal location for these measurements as the blood vessels are not optimally near the surface, and movement from physical activity can cause measurement errors.

Instead, ear canals might be a better host. They boast vasculature close to the skin and sufficient blood flow for high-quality measurements. An essential first step to building ear physiological trackers is to understand the ear’s vascular distribution. Hong et al. used optical coherence tomography angiography (OCTA) to image and analyze blood flow in human ears.

“The ear canal has been suggested as a promising measurement site for physiological parameters that can potentially combine minimal invasiveness and wearability with reliable and accurate recordings in a variety of settings,” said author Juyeon Hong. “However, despite extensive research on hearable technologies within the outer ear, there is a lack of research in the field of vascular imaging and quantitative analysis in the outer ear in vivo.”

The team designed a probe to obtain OCTA images of three regions of the human ear with relatively dense blood vessel distribution. The resulting cross-sectional images mapped the vascular structure of the ears of ten volunteers and isolated 20 variables for characterizing the maps. They also demonstrated the potential for OCTA for monitoring pulsatile blood flow.

“This research represents preliminary results of highly accurate hearable sensor positioning with measurement of vascular distribution using OCTA,” said Hong. “We plan to conduct further research to integrate the hearable sensor with hearing devices for continuous health monitoring.”

Source: “Imaging of the vascular distribution of the outer ear using optical coherence tomography angiography for highly accurate positioning of a hearable sensor,” by Juyeon Hong, Daewoon Seong, Dongwan Kang, Hyunmo Kim, Jeong Hun Jang, Mansik Jeon, and Jeehyun Kim, APL Bioengineering (2024). The article can be accessed at https://doi.org/10.1063/5.0203582 .