Abstract: This paper describes the preliminary case study on the effect of the electromagnetic interference (EMI) and radiation interaction on implantable pacemaker. Temperatures were calculated at certain frequencies to investigate the effect in human's body. Higher temperatures may cause discomfort to the patient and malfunction to the pacemaker. Hence, the analytical model that mimic of implantable heart pacemaker is being developed to measure the EMI level through the implementation of FDTD method.
INTRODUCTION
Recent development in wireless mobile communications has generated awareness in electromagnetic interferences for medical devices such as implantable pacemaker. The impact of the interference may cause these devices to malfunctions with potentially adverse consequences. The study of electromagnetic interference and radiation to human health has led to major changes in beliefs regarding the risk that may involve in modification [1].
Ability of using mobile cellular phones at wide coverage, timelessly led to its necessary used in daily life. The convenience of being able to communicate with anyone from anywhere at any time has become part of our modern lifestyle. Most cellular phones have either a small antenna attached or integrated into internal parts. The antenna in mobile cellular phones produced greater Radio Frequency (RF) exposure than other types of RF systems through transmit and receive data [2]. A portion of exposed radiation absorbed by tissues to the nearest region of human's body from the energy sources and some other portion is radiated away into the surrounding air space.
Excessive exposure to RF fields can cause heating of human tissues that leads to an increase in body temperature. Although body has its own effective ways of regulating body temperature, nevertheless, if the radiation exposures are too high (over than 2Gy), the body may no longer be able to cope. As a consequence, the rising thermal may cause malfunction to the implantable pacemaker and affects irritation, discomfort and an illness to patient's health
PACEMAKER
Implantable pacemakers are prescribed for individual of all ages whose has irregular hearts beat. Nearly over 2 million pacemakers have been implanted worldwide since 1960 [3]. The increasing numbers of existence senior citizens, it is anticipated that a greater percentage of the population will require pacemakers.
Imputable to current technology, pacemaker implantation has become much easier and safer. For future direction, much advancement will be making to enhance the control of the pacemaker once it is implanted in the human body. As research efforts continue, future pacemaker promises to be long lasting, more reliable, and more versatile. Advances and developments in biomedical and electronics sector should provide even smaller medical devices which are less prone to environmental interferences.
This implantable pacemaker is a battery-operated electronic biomedical device that capable to normalize the human heartbeats when its natural regulating mechanisms break down [4]. It provides electric impulses that mimic the natural human heartbeats. The device is inserted under the skin to help the heart to contract and to pump blood throughout the body at an appropriate rate.
Implanted pacemaker device
Pacemaker normally implanted in human chest cavity where its' electrode has direct contact with the heart as shown in Figure 1. The electronic circuitry in pacemaker will determine a pacing pulse through a sensing device. The sensor will turns the signal off when the heartbeat is above a certain level, and turns the signal back on when the heartbeat is under par.
Pacemaker Generator
The pulse generator case of the pacemaker is made of titanium. It has high modulus of elasticity, high resistance to corrosion and also high durability. It also contains one to three insulated thin wires that travel through a vein in the chest to the heart.
A pacemaker generator consists of battery, circuitry and connector block. Battery supplies the electrical energy for pacing or sending of tiny electrical pulses in pacemakers. The small and lithium sealed battery typically can last from 4 to 8 years [5], depending on the active passive usage. The entire pacemaker requires complete change if the battery is low.
The electronic circuitry of pacemakers transforms the energy from the battery into tiny electrical pulses. It controls timing of the electrical pulses and amount of energy delivers to the heart. Connector block, a transparent plastic located on top of the pacemaker's metal container to connect the pacing lead with the pacemaker.
Pacing Lead
Pacing lead is a flexible insulated wire that connected to a pacemaker. The lead is capable to hold the twist and bend of the wire caused by body movement and motion by the heart itself.Pacing lead carries a tiny electrical pulse from pacemaker to the heart and relays information about the heart's electrical activity back to the device. The lead consists of connector pin, lead body, fixation mechanism and electrode. The lead normally inserted through a vein and guided into the right ventricle of the heart. This is known as endocardial lead or a transvenous lead. In certain cases, the lead is attached to the outside of the heart and it is called epicardial lead. An epicardial lead is often used for kids due to the growth of child's body system.
The pacemaker and the pacing lead work together to perform two main functions i.e pacing and sensing. A pacing system restores the rhythm of human heart. The pacemaker paces or sends a pacing pulse to the heart if sensing system detects natural rhythm is interrupted, irregular or too slow.
ELECTROMAGETIC INTERFERENCE (EMI) AND RADIATION INTERACTION
Electromagnetic interference (EMI) due to RF is known to cause interference in electronics devices. Exposure to EMI occurs from these gadgets may cause pacemaker to malfunctions with potentially adverse consequences. These depend on the strength of the electromagnetic field, the exposure duration, sources frequency and distance.
The Specific Absorption Rates (SARs) quantifies and registers localization of deposited microwave energy absorbed in human tissues [6]-[7]. It indicates the average rate at which energy is absorbed for each kilogram of tissue (watt per kg) and given by
where is Plank's constant which has a value of . Planck's Law of black-body radiation describes the amplitude of radiation emitted i.e spectral radiance of electromagnetic radiation at all wavelengths from a black body at temperature, and can be derived as
where is speed of light with a value of and is Boltzmann's constant with a value of .
In this study, radiation from digital cellular phone at frequencies of and are radiated to human tissues at heart area and also ear area. The initial conditions for temperatures equal to ambient air, and the temperature of blood is constant at. Results of SAR values absorbed by human tissues in heart area are shown in Figure 2. From the result, it shows that the highest SAR values in both frequencies are in blood tissues where and respectively. Figure 3 shows the temperature radiated at ear area when increasing of time. From the graph, it shows that maximum temperature at is rising to, while at frequencies is for. Both simulation results shows that implanted pacemaker in human heart respond respect to temperature rises.
Future WORK AND RESEARCH
The direction for future work of the study is to develop an analytical model that mimics the artificial implantable pacemaker and later will be analyzed to measure the EMI level through the implementation of Finite-Difference Time Domain (FDTD) method [8]. Figure 4 shows a schematic analytical diagram of implantable pacemaker circuitry that being developed in the study. The modeling of circuit design is based on its main operation to stimulate heart beat and location of interference which is affected by condition of the switch; either closed (charging) or open switch (discharging).
Pacemaker is represented by voltage source, radiation impedance and the heart impedance source. A pacemaker lead and the body tissue itself represent the wiring connecting the heart to the pacemaker. The lead impedance becomes useful piece of information, as dramatic changes in it may indicate a problem in the pacemaker circuit. The radiation impedance can be obtained through the source voltage at the connector to drive the electrode and lead wire against the shielded housing. The interference voltage through the connector to the input of the internal pacemaker circuit can be determined by
CONCLUSION
The development of wireless communications and the widespread use of digital cellular phones have motivated a great concern about possible effects of the electromagnetic radiation on the user's health and also biomedical devices such as implantable pacemaker. In this paper, the simulation results shows that implanted pacemaker in human heart respond respect to temperature rises. As a consequence, the increasing of temperatures can caused pacemaker malfunctions and affects illness to patient's health. In addition, the preliminary analytical model that mimic of implantable heart pacemaker is presented. It is believed that this analytical model can be utilized to measure the EMI level through the implementation of FDTD method.
