Design and Development of a Low Cost Personal Computer Based ECG Monitor

Abstract

ECG equipment is vital for diagnosis of cardiac problems. However, such equipment come from the rich Western countries at a huge cost in both procurement and maintenance, and therefore cannot offer services to a large population in the Third World countries. The only solution is to design and develop such equipment in individual countries by developing local expertise. With three decades of experience, the Dhaka University group has taken a step towards developing prototypes of ECG equipment for dissemination to the healthcare service providers. This paper presents the detailed design of an PC based ECG equipment where optimized choice of components and of the design have been made keeping the cost and maintenance in view, but not sacrificing the quality, and incorporating necessary safety features to protect the patient from known hazards. Both the hardware and the software have been developed locally and are detailed in this paper. Outputs obtained from human subjects are shown which are of reasonable good quality, and have been verified using standard ECG equipment. The PC based ECG system will allow digital post processing of signals for improved diagnosis through software. Besides, this can also become part of a nationwide telemedicine system. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14701 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 115-125

Design and Development of a PC based ECG Equipment

“…(Rabbani et al 2011). The ECG equipment will communicate with a PC through its USB port and will be powered from the PC through the same port as well, so that no external power will be required to drive the ECG equipment.…”

“…It has a high Common Mode Rejection Ratio (CMRR), about 80 dB or more, and the 50 Hz signal can be reduced significantly with respect to the desired ECG signal. The ins-amp also minimises the voltage drop across the contact impedances of the skin electrodes, typically 10Kohms at low frequencies, to a negligible level (Rabbani et al 2011).…”

“…Obviously, this switching will be performed for analogue signals, and one has to take care that the sizes and shapes of the signals are maintained. The total input resistance seen by the two inputs of the instrumentation amplifier should be closely matched, otherwise voltage drop across the input resistors due to noise sources will contribute to a differential noise potential resulting in increased noise in the ECG (Rabbani et al 2011). This requires careful planning and calculation in the choice of the resistor network.…”

“…Since the PC is normally powered by mains supply, the ECG device circuit must be divided into electrically isolated (from mains ac) patient side and non-isolated PC side (Rabbani et al 2011). Both the power and the signal need to be electrically isolated.…”

“…Most of the modern medical equipment use microcontrollers with firmware controlled design, and for trade secrecy, the manufacturers do not provide technical details or proper repair manuals, thus making local repairs almost impossible. In many rural hospitals in Third World countries like Bangladesh, either there is no ECG equipment, or if there is one, it is probably out of order (Rabbani et al 2011). Therefore, it is necessary that such equipment are designed and developed indigenously in each country for local manufacture and distribution.…”