胸腔生物阻抗检测对人体植入电子设备安全性研究

Safety Evaluation of Thoracic Bio-Electrical Impedance Technique

全球范围内佩戴心脏植入电子设备的患者日益增加,采用生物电阻抗技术进行病理检测,可能会对心脏植入电子设备患者产生干扰。该文建立生物电阻抗交流激励系统及心脏起搏电极仿真模型,完成胸腔生物阻抗检测技术对心脏起搏器电磁干扰的安全性研究。仿真研究表明,胸腔生物阻抗测量引起的电压干扰超过了ISO 14117标准中定义的最大阈值,且干扰水平随着生物阻抗激励信号的频率和电极位置的不同而变化,并且组织电特性也会对干扰水平产生影响。生物电阻抗技术可能会对心脏植入电子设备存在潜在干扰,不建议在该人群中使用胸腔阻抗法进行检测。

Due to the increasingly serious aging society and environmental factors,the incidence of cardiovascular diseases is increasing year by year.According to data from the 25th National Forum on Interventional Cardiology,the number of pacemaker implants in China reached 99000 units,a year-over-year increase of 15.1%in 2021.Cardiac implantable electronic devices contain multiple microcircuits,easily affected by medical devices such as magnetic resonance imaging,electrosurgery,and bio-electrical impedance.With the development and application of bio-electrical impedance technology,attention should be paid to electromagnetic interference.The alternating high-frequency signal is the core part of the bioelectrical impedance excitation system.When an alternating current is applied to the electrode,an alternating electric field is generated between the two electrodes,filling the entire space.Current is constrained by external excitation and space of electromagnetic field.Firstly,a 3D simulation model based on a simplified pacemaker electrode model and real thoracic.Secondly,the dielectric properties of biological tissue are set according to the website of dielectric properties of human tissues and organs.Thirdly,inject 5 mA current excitation at 4,6,10,25,40,63,and 100 kHz.The excitation electrode is arranged near the 5th frame.To obtain the induced voltage that has the greatest influence on the pacemaker electrode,the excitation electrode and the pacemaker electrode are set at the same level,and the configuration form is adjacent,opposite,and cross,respectively.In this way,the induced voltage values of the pacemaker electrode under different excitations are obtained.Simulation results show that the level of electrical interference varies with frequency between 4 kHz and 100 kHz.The induced voltage of the expiratory state is lower than that of the inspiratory state.The tissue characteristics in the model are taken from the same database,and the interference degree is different due to the location of the excitation electrode.The interference of cross-excitation configuration is the highest,and the interference of adjacent excitation is the least.When the excitation frequency is 100 kHz,the interference is significantly reduced,and the data does not exceed the maximum voltage amplitude threshold.Overall,the interference in the inhaling state of the lung is higher than that in the exhaling state of the lung.The higher the excitation frequency,the smaller the induced voltage interference.A plastic circular cavity with salt water is used to simulate the chest cavity and tissue,and the titanium rod is in the salt water.The interference of input excitation to the resistance rod can be observed on the oscilloscope.It is found that the induced voltage on the resistance rod decreases gradually with the increase of frequency by changing the injected electrode.The changing trend is consistent with the human chest cavity model.The following conclusions can be drawn from the simulation analysis:(1)The level of electrical interference varies with frequency.The lower the excitation frequency,the stronger the interference.(2)The interference level of electrodes is different in different positions.The interference is strongest in cross-electrode configuration and weakest in adjacent.(3)Some induced voltages exceed the maximum threshold voltage specified in ISO 14117.Potential electromagnetic interference exists in patients with cardiac pacemakers.Since interference may affect the pacemaker’s normal operation and cause serious events,the thoracic bio-impedance method is not recommended for testing on pacemaker wearers.