Understanding EKG Electrodes: Part 1 of 3: Chemistry
All the technical developments behind the EKG machine would be meaningless if not for one thing: the electrode connecting the EKG machine to the patient. Electrode technology is a mixture of chemistry, physics and electronics. In this part of this three part series, we will be discussing the chemistry.
The electric currents that an EKG machine is concerned with are minuscule, especially when compared to the amounts of electricity that we deal with on a daily basis. Given that, how can they be picked up, much less detected and interpreted?
It begins with chemistry, not the biochemistry of the human body, but the chemistry of electrons. All atoms have electrons, either tightly bound to the rest of the atom, or loosely bound. The looser the binding, the easier these electrons can move from one atom to another. This is the reason behind the formation of chemical compounds, whether slowly as in rust, or quickly as in combustion, or, for that matter, very rapidly, as with an explosion. But what we are concerned with is the electron capacity of metals.
Metals are in part defined by a particular state of electrons called delocalized electrons. They are neither tightly bound or loosely bound, but extend across several atoms in an orbit. This is not just a footnote of chemistry. This is the basis of metals’ ability to conduct electricity.
When the electron orbit of one group of atoms is lined up with another orbit from another group of atoms, it forms an even bigger orbit. Multiply this over the length of a piece of metal, a wire for example, and you have now a giant cloud of electrons. The great thing about this cloud is the way it can pass electrons along from one end to another. The passing of electrons is a good model: it is as much a pull from the electrons in the metal itself as it is a push from an outside source.
What all this means for an EKG machine is that certain metals with a high degree of electron activity can pass along very small charges, and pass them along will little change. This is the chemistry that begins the EKG process.
Be sure to read the two additional articles in this series on Physics and Electronics.
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