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area offocus( Nazarian et al., 2006; Nordbeck et al., 2009; Strom et al., 2017; Zeng et al., 2019). In recent years, studies have been carried out on newly applied technologies, such as wireless communication and charging( Seidman et al., 2014; Seckler et al., 2015; Mattei et al., 2016), electrical vehicle and its charger( Tondato et al., 2017; Lennerz et al., 2023; Wase, 2023), transcutaneous electrical nerve stimulation( Badger et al., 2017; Egger et al., 2019; Suhail Arain et al., 2023), and small rare-earth magnets used inside electronic devices( Seidman et al., 2021). However, few studies have prioritized the assessment for power frequencies. Given the number of workers carrying CIEDs( i. e., CIED-employees) continues to increase and their inevitable presences in the workplaces, concerns have been expressed regarding potential dysfunctions of implanted medical devices that may be associated with exposure to high-intensity electric and magnetic fields generated by the transmission, distribution, and utilization of electricity.
In general, exposure to EMFs is considered safe in environments accessible to the public. However, in the workplace, exposures are various and may be higher. CIEDemployees are especially susceptible to EMFs and factors such as device sensitivity, implantation configuration, and pacing technology can all affect the performance of CIEDs. To ensure their safety in the workplace, it is important that occupational physicians evaluate each case individually. The European Standard series EN 50527 has then standardized the process of evaluating the exposure of active implantable medical devices( AIMDs) to EMFs. This standard brings up the need for establishing a non-clinical investigation that is simple, reproducible, and risk-free, ensuring effective and consistent risk assessments in the workplace.
In this paper, we established a setup for evaluating occupational hazards associated with cardiac implants exposed to high-intensity EFs at low frequencies in the workplace. Correspondences were built up between in vitro testing and real-case exposures to conduct non-clinical investigation in the risk assessment. A voltage injection system( VIS) was proposed as an on-site solution in the workplace to conduct effective equivalent tests. The VIS assessment allows us to reduce the complexity of the study under EF exposures, which is restrictive in terms of high-intensity voltage, installations, and safety protocols. By using this system, employers can perform simpler tests with reproducible perturbations, thereby facilitating more straightforward and consistent risk assessments. VIS assessment were conducted on four cardiac implants( two PMs and two ICDs) with the presence of cardiac signals, as a demonstration of its application.
2 Materials and methods
2.1 Assessment process in the framework of EN 50527
For a certain case to be assessed, the European Standard EN 50527 indicates a general risk assessment above all in order to determine whether a specific assessment process is necessary. The manufacturers guarantee the immunity of CIEDs conforming to EN 45502 and ISO 14117, which provide safety requirements and technical electromagnetic compatibility test protocols for manufacturers to follow. CIEDs entering the European market are expected to operate without interference as long as the General Public Reference levels of Council Recommendation 1999 / 519 / EC are not exceeded. If the exposure is higher, no risk assessment is required if a responsible physician has confirmed that a sufficient history of uninfluenced behavior at the workplace exists to exclude clinically significant interaction. Otherwise, a specific risk assessment for the CIED-employee is required.
In the specific assessment process, information relevant to the equipment producing EMFs, information collected from the responsible physician, and clinical details about the CIEDemployee, such as their dependency on the CIED, are taken into consideration.. If this information fails to exclude risk to the CIED-employee of the EMI at the workplace, an additional investigation is necessary. The additional investigation can be conducted in either clinical method( or in vivo) or non-clinical methods( in vitro or comparative study). Considering complex environments and individual situations, the clinical method might be contraindicated in some circumstances. In consequence, non-clinical investigation shall be carried out. At the end, a final report of the investigation shall be written, containing all the methods applied, the findings and the conclusions from the process.
2.2 Non-clinical investigation method
The EN 50527-2-1 for pacemakers and the EN 50527-2-2 for ICDs proposed in vitro testing as one among the investigation approaches. Interference thresholds may be obtained through provocative studies( Gerçek et al., 2020; Zhou et al., 2022). Due to the inhomogeneity of the human body, reproducing the complex variations of induction in the EF exposure using homogeneous phantom material is challenging. To address this issue, a funnel-shaped phantom was used to replicate the induction in the chest and in the heart( where cardiac implants are typically installed) due to its geometric design. This phantom has been employed in the interference investigation for cardiac implants by in vitro testing under laboratory EF exposures, with equivalence factors of 2.39 for unipolar sensing and 3.64 for bipolar sensing. These equivalence factors describe the ability to substitute the real case while retaining important characteristics. This laboratory EF exposure system was established in the laboratory capable of producing exposure up to 50 kV / m( equivalent to 119.5 kV / m in unipolar sensing and 182 kV / m in bipolar sensing in real case), however, requiring strict experimental environment and security protections( Zhou, 2023).
To provide an accessible approach for employers in the workplace, we have established a voltage injection system( VIS) using the same funnel-shaped phantom( Fig. 1A). This setup is expected to produce similar induction in the phantom without a complex configuration as for the laboratory EF exposure. A metal grid with a diameter of 280 mm was placed on top of the phantom solution, with a banana socket on the top to fix the injection cable( Fig. 1B). Voltages were injected into the grid from a generator to produce EF induction in the phantom, while the phantom base was connected to the common ground of the setup. We used the digital lock-in amplifier HF2IS from Zurich Instruments TM( Zurich, Switzerland) to generate small-scale voltage injections while