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Chapter 7 Working Principle
7.1 How to Obtain High Quality ECG and Accurate Heart
Rate Value
The electrocardiogram (ECG or EKG) is primarily a tool for evaluating the electrical events within the
heart. The action potentials of cardiac-muscle cells can be viewed as batteries that cause charge to
move throughout the body fluids. These currents represent the sum of the action potentials occurring
simultaneously in many individual cells and can be detected by recording electrodes at the surface of
the skin. The figure below shows the system of the heart.
First of all, the hospital should be equipped with a 100~250V power supply system with a typical
grounding wire. If big interference in ECG continues, connect one end of the grounding wire provided
with this equipment to the grounding wire on the back panel of this monitor, and the other end to the
special grounding wire, water pipe or radiator.
A common ECG plate electrode used together with this monitor has short shelf life. Generally, the
shelf life is only one month after the package is opened. When outdated plate electrode is used, due
to skin’s contact impedance and big electrode potential, the chance of interference will be increased,
and the ECG baseline will have an unstable inclination. Therefore, always use valid plate electrodes.
7.2 The Principle of NIBP Measurement
Blood pressure may be measured in an invasive way (whereby the sensor will be inserted into
blood vessel directly) or a non-invasive way. The non-invasive way includes several