Monitoring of the central blood pressure waveform via a conformal ultrasonic device

Abstract

Continuous monitoring of the central blood pressure waveform from deeply embedded vessels such as the carotid artery and jugular vein has clinical value for the prediction of all-cause cardiovascular mortality. However, existing non-invasive approaches, including photoplethysmography and tonometry, only enable access to the superficial peripheral vasculature. Although current ultrasonic technologies allow non-invasive deep tissue observation, unstable coupling with the tissue surface resulting from the bulkiness and rigidity of conventional ultrasound probes introduces usability constraints. Here, we describe the design and operation of an ultrasonic device that is conformal to the skin and capable of capturing blood pressure waveforms at deeply embedded arterial and venous sites. The wearable device is ultrathin (240 μm) and stretchable (with strains up to 60%), and enables the non-invasive, continuous and accurate monitoring of cardiovascular events from multiple body locations, which should facilitate its use in a variety of clinical environments.

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Fig. 1: Design and working principle of the stretchable ultrasonic device.
Fig. 2: Electrical, mechanical, acoustic and biocompatibility characterizations of the conformal ultrasonic device.
Fig. 3: Comparison between the conformal ultrasound sensor and a commercial tonometer, exercise haemodynamics monitoring and central arterial and venous pulse measurements.
Fig. 4: BP measurements from the central to peripheral arteries and validation using a commercial tonometer.
Fig. 5: ECG correlation-based PWV calculation to evaluate arterial stiffness.

Data availability

The main data supporting the findings of this study are available within the Article and its Supplementary Information. The raw data generated in this study are available from the corresponding author upon reasonable request.

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Acknowledgements

The project was supported by the National Institutes of Health (NIH, grant R21EB025521) and the Center for Wearable Sensors at the University of California, San Diego. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. All bio-experiments were conducted in accordance with the ethical guidelines of the NIH and with the approval of the Institutional Review Board of the University of California, San Diego (IRB no. 170812). The authors thank K. Anagnostopoulos and H. Kim for discussions and advice regarding Picoscope DAQ, A. Kahn for discussions on PWV measurements, E. Topol, S. Steinhubl and E. Muse for stimulating discussions on ambulatory BP measurement, Q. Yang and R. Lal for mechanical vibration characterization of the 1–3 composite material, and S. Xiang for constructive feedback on manuscript preparation.

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Chonghe Wang and S.X. designed the research. Chonghe Wang, X.L., M.L., Z.Z. and H.H. performed the experiment. Chonghe Wang performed the simulation. Chonghe Wang, M.L., Z.Z. and X.L. analysed the data. Chonghe Wang, Z.Z. and S.X. wrote the paper. All authors provided active and valuable feedback on the manuscript.

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Correspondence to Sheng Xu.

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Wang, C., Li, X., Hu, H. et al. Monitoring of the central blood pressure waveform via a conformal ultrasonic device. Nat Biomed Eng 2, 687–695 (2018). https://doi.org/10.1038/s41551-018-0287-x

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