Abstract
Most cardiovascular diseases, such as arteriosclerosis and hypertension, are directly linked to pathological changes in hemodynamics, i.e. the complex coupling of blood pressure, blood flow and arterial distension. To improve the current understanding of cardiovascular diseases and pave the way for novel cardiovascular diagnostics, innovative tools are required that measure pressure, flow, and distension waveforms with yet unattained spatiotemporal resolution. In this context, miniaturized implantable solutions for continuously measuring these parameters over the long-term are of particular interest. We present here an implantable photonic sensor system capable of sensing arterial wall movements of a few hundred microns in vivo with sub-micron resolution, a precision in the micrometer range and a temporal resolution of 10 kHz. The photonic measurement principle is based on transmission photoplethysmography with stretchable optoelectronic sensors applied directly to large systemic arteries. The presented photonic sensor system expands the toolbox of cardiovascular measurement techniques and makes these key vital parameters continuously accessible over the long-term. In the near term, this new approach offers a tool for clinical research, and as a perspective, a continuous long-term monitoring system that enables novel diagnostic methods in arteriosclerosis and hypertension research that follow the trend in quantifying cardiovascular diseases by measuring arterial stiffness and more generally analyzing pulse contours.
Highlights
The development of flexible and stretchable sensor systems that comply with the soft mechanical properties of tissue opens new ways in biomedical engineering [1, 2]
Sonomicrometry estimates arterial distension from the transit time of an ultrasonic pulse traveling between two piezo-crystals that are diametrically placed at the arterial wall using surgical sutures [12]
pulse wave velocity (PWV) and pulse arrival time (PAT) provide a regional measure over larger segments of the arterial tree and may be a more versatile measure to correlate with cardiovascular disease pathology
Summary
The development of flexible and stretchable sensor systems that comply with the soft mechanical properties of tissue opens new ways in biomedical engineering [1, 2]. Sonomicrometry estimates arterial distension from the transit time of an ultrasonic pulse traveling between two piezo-crystals that are diametrically placed at the arterial wall using surgical sutures [12]. In contrast to standard clinical practice, the measurement site of the PPG is moved from the fingertip or earlobe directly to large arteries It is realized by the fabrication of a miniaturized, stretchable photoplethysmograph that is inspired by recent advancements in the field of stretchable electronics [2, 15]. The capability of this sensor system in measuring arterial distension is presented by in vitro and in vivo experiments. The distension data gives new insight into the biomechanics of the arterial wall and provides an implantable solution to quantify the key risk factor for cardiovascular events, arterial stiffness [16]
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