Flexible Adaptive Sensing Tonometry for Medical-grade Multi-parametric Hemodynamic Monitoring
Authors: Tingrui Pan, Mengkang Deng, Chentao Du, Jiayuan Fang, Changshun Xu, Chenhui Guo, Jiantao Huang, Kang Li, Lei Chen, Yuan-Ting Zhang, Yu Chang
Continuous hemodynamic monitoring in a wearable means can play a crucial role in managing hypertension and preventing catastrophic cardiovascular events. In this study, we have described the first wearable tonometric device, referred to as flexible adaptive sensing tonometry (FAST), which is capable of continuous and accurate monitoring of hemodynamic parameters within the medical-grade precision. In particular, the FAST system integrates a 1×8 unit array of highly sensitive and highly flexible iontronic sensing (FITS) with 1mm spatial resolution and a closed-loop motion system. The flexible tonometric architecture has been used to determine the radial arterial position with high sensitivity and high conformability, which simplifies the biaxial searching process of the traditional applanation tonometry into a highly efficient uniaxial applanation while keeping the medical-precision assessments. Importantly, a self-calibration algorithm can be automatically implemented during the applanation process, from which the intra-arterial blood pressure wave can be continuously predicted within the medical-grade precision, and subsequently, multi-parametric hemodynamic analysis can be performed in real-time. Experimental validations on health volunteers have demonstrated that the FAST measurements are all within the required accuracy of the clinical standards for continuous pulse wave assessments, blood pressure monitoring as well as other key hemodynamic parameter evaluations. Therefore, the FAST system, by integrating the flexible iontronic sensing array, provides a real-time, medical-grade hemodynamic monitoring solution in a continuously wearable manner, from which remote patient-centered monitoring can be delivered with both medical precision and convenience.
Fig. Characterization of radial arterial pulse simulator and the determination of radial arterial location (a) The device illustration and (b) the control block diagram of the pulse simulator. (c) Comparison of the simulated pulse waveforms generated by the Fluke device (from 0-4sec) and those produced by the pulse simulator (from 4-8sec). Different key features of the simulated pulse waveforms are marked. (d) Pulse waveform with typical heart rate (HR) from the simulator. Columns (left to right): 60BPM (Case1), 70BPM (Case2) and 80BPM (Case3). (e) Result of HR experiments from Case1 to Case3. Error bars represent ±SD. (f) Pulse waveform with typical heart systolic and diastolic blood pressure (SBP/DBP) from the simulator. Columns (left to right): 100/60mmHg (Case4), 120/80mmHg (Case5) and 150/100mmHg (Case6). (g) Result of SBP/DBP experiments from Case4 to Case6. Error bars represent ±SD. (h) Pulse waveforms with different interval times between the systolic peak and the dicrotic notch. Columns (left to right): 150ms (Case7), 300ms (Case8) and 450ms (Case9). (i) Result of the interval times from Case7 to Case9. Error bars represent ±SD. (j) Schematic of the FITS array placed on the artificial vessel of the simulator. (k) Distribution of pulse wave amplitudes at different placement locations.
Keywords: Flexible electronics, hemodynamic monitoring, iontronic sensing, wearable devices, pressure control, microfluidics