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Remote monitoring of heart failure patients using intravascular implants may enable early detection of disease worsening and reduce hospitalizations \cite{Mohebali_Kittleson_2021}. Within the FORESEE project, a multiparametric pulmonary artery sensor is being developed for wireless powering and communication through volume conduction \cite{Becerra-Fajardo_Minguillon_Krob_Rodrigues_González-Sánchez_Megía-García_Galán_Henares_Comerma_del-Ama_et al._2024}, \cite{García-Moreno_Comerma-Montells_Tudela-Pi_Minguillon_Becerra-Fajardo_Ivorra_2022}. In this approach, harmless high-frequency current bursts ($6.78$ MHz) are applied across the torso using textile electrodes, and the implant is powered through two pick-up electrodes located at its ends.
The feasibility of this powering strategy was assessed by means of computational modeling. A three-dimensional adult human torso model, including the pulmonary artery, was used for electromagnetic simulations (COMSOL Multiphysics). The influence of implant electrode exposed area, implant length, and implant position was analyzed while ensuring compliance with electrical safety criteria (SAR $\le 10$ W/kg). Additional simulations considered physiological variability, different respiratory cycle states and adipose tissue thickness.
The results showed that more than 5 mW can be safely delivered to the implant, sufficient to power the sensor electronics. Although adipose tissue thickness and implant alignment were identified as critical factors, the study supports the feasibility of safely powering a pulmonary artery intravascular sensor using volume conduction.
Bibliography
@article{Mohebali_Kittleson_2021, title={Remote monitoring in heart failure: current and emerging technologies in the context of the pandemic},
volume={107},
ISSN={1355-6037, 1468-201X},
url={https://heart.bmj.com/lookup/doi/10.1136/heartjnl-2020-318062},
DOI={10.1136/heartjnl-2020-318062},
abstractNote={The incidence of heart failure (HF) remains high and patients with HF are at risk for frequent hospitalisations. Remote monitoring technologies may provide early indications of HF decompensation and potentially allow for optimisation of therapy to prevent HF hospitalisations. The need for reliable remote monitoring technology has never been greater as the COVID-19 pandemic has led to the rapid expansion of a new mode of healthcare delivery: the virtual visit. With the convergence of remote monitoring technologies and reliable method of remote healthcare delivery, an understanding of the role of both in the management of patients with HF is critical. In this review, we outline the evidence on current remote monitoring technologies in patients with HF and highlighthow these advances may benefit patients in the context of the current pandemic.},
number={5},
journal={Heart},
author={Mohebali, Donya and Kittleson, Michelle M},
year={2021},
month=mar,
pages={366–372},
language={en} }
@article{Becerra-Fajardo_Minguillon_Krob_Rodrigues_González-Sánchez_Megía-García_Galán_Henares_Comerma_del-Ama_et al._2024, title={First-in-human demonstration of floating EMG sensors and stimulators wirelessly powered and operated by volume conduction},
volume={21},
ISSN={1743-0003},
url={https://jneuroengrehab.biomedcentral.com/articles/10.1186/s12984-023-01295-5}, DOI={10.1186/s12984-023-01295-5},
%abstractNote={Abstract Background Recently we reported the design and evaluation of floating semi-implantable devices that receive power from and bidirectionally communicate with an external system using coupling by volume conduction. The approach, of which the semi-implantable devices are proof-of-concept prototypes, may overcome some limitations presented by existing neuroprostheses, especially those related to implant size and deployment, as the implants avoid bulky components and can be developed as threadlike devices. Here, it is reported the first-in-human acute demonstration of these devices for electromyography (EMG) sensing and electrical stimulation. Methods A proof-of-concept device, consisting of implantable thin-film electrodes and a nonimplantable miniature electronic circuit connected to them, was deployed in the upper or lower limb of six healthy participants. Two external electrodes were strapped around the limb and were connected to the external system which delivered high frequency current bursts. Within these bursts, 13 commands were modulated to communicate with the implant. Results Four devices were deployed in the biceps brachii and the gastrocnemius medialis muscles, and the external system was able to power and communicate with them. Limitations regarding insertion and communication speed are reported. Sensing and stimulation parameters were configured from the external system. In one participant, electrical stimulation and EMG acquisition assays were performed, demonstrating the feasibility of the approach to power and communicate with the floating device. Conclusions This is the first-in-human demonstration of EMG sensors and electrical stimulators powered and operated by volume conduction. These proof-of-concept devices can be miniaturized using current microelectronic technologies, enabling fully implantable networked neuroprosthetics.},
number={1},
journal={Journal of NeuroEngineering and Rehabilitation},
author={Becerra-Fajardo, Laura and Minguillon, Jesus and Krob, Marc Oliver and Rodrigues, Camila and González-Sánchez, Miguel and Megía-García, Álvaro and Galán, Carolina Redondo and Henares, Francisco Gutiérrez and Comerma, Albert and del-Ama, Antonio J. and Gil-Agudo, Angel and Grandas, Francisco and Schneider-Ickert, Andreas and Barroso, Filipe Oliveira and Ivorra, Antoni},
year={2024},
month=jan,
pages={4},
language={en} }
@article{García-Moreno_Comerma-Montells_Tudela-Pi_Minguillon_Becerra-Fajardo_Ivorra_2022,
title={Wireless networks of injectable microelectronic stimulators based on rectification of volume conducted high frequency currents},
volume={19},
ISSN={1741-2560, 1741-2552},
url={https://iopscience.iop.org/article/10.1088/1741-2552/ac8dc4}, DOI={10.1088/1741-2552/ac8dc4},
%abstractNote={Abstract Objective. To develop and in vivo demonstrate threadlike wireless implantable neuromuscular microstimulators that are digitally addressable. Approach. These devices perform, through its two electrodes, electronic rectification of innocuous high frequency current bursts delivered by volume conduction via epidermal textile electrodes. By avoiding the need of large components to obtain electrical energy, this approach allows the development of thin devices that can be intramuscularly implanted by minimally invasive procedures such as injection. For compliance with electrical safety standards, this approach requires a minimum distance, in the order of millimeters or a very few centimeters, between the implant electrodes. Additionally, the devices must cause minimal mechanical damage to tissues, avoid dislocation and be adequate for long-term implantation. Considering these requirements, the implants were conceived as tubular and flexible devices with two electrodes at opposite ends and, at the middle section, a hermetic metallic capsule housing the electronics. Main results. The developed implants have a submillimetric diameter (0.97 mm diameter, 35 mm length) and consist of a microcircuit, which contains a single custom-developed integrated circuit, housed within a titanium capsule (0.7 mm diameter, 6.5 mm length), and two platinum–iridium coils that form two electrodes (3 mm length) located at opposite ends of a silicone body. These neuromuscular stimulators are addressable, allowing to establish a network of microstimulators that can be controlled independently. Their operation was demonstrated in an acute study by injecting a few of them in the hind limb of anesthetized rabbits and inducing controlled and independent contractions. Significance. These results show the feasibility of manufacturing threadlike wireless addressable neuromuscular stimulators by using fabrication techniques and materials well established for chronic electronic implants. Although long-term operation still must be demonstrated, the obtained results pave the way to the clinical development of advanced motor neuroprostheses formed by dense networks of such wireless devices.},
number={5},
journal={Journal of Neural Engineering},
author={García-Moreno, Aracelys and Comerma-Montells, Albert and Tudela-Pi, Marc and Minguillon, Jesus and Becerra-Fajardo, Laura and Ivorra, Antoni},
year={2022},
month=oct,
pages={056015} }
