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During the development of the string galvanometer, its size also was decreased from 600
lbs in 1903 to 30 lbs in 1928. Just think of the times we use to complain about the weight of
the lifepack 4, as we carried it in and out of the ambulances.
The next improvement came with modification of the electrodes. Einthoven's original cylinders of electrolyte solutions were reduced in size and still in use as late as 1930. Alfred
Cohn in 1920 introduced the strap on electrode in the United States. In 1930 the Cambridge
Instrument Company of New York introduced the German silver direct-contact plate electrodes. A suction electrode was developed by Rudolph Burger in 1932 for the precordial
leads. This was later modified by Welsh and is now the suction cup we currently use with
our 12 lead machines.
The next stage in the development of the ECG machine lead to the use of the vacuum tubes
for amplification. The first one of this type developed in the United States was by the General Electric Corporation. The cathode-ray tube was next introduced into electrocardiography. This improved the physical characteristics of the recorders,
The introduction of the amplifier-type electrocardiographs led to the development of the direct-writing instruments. As you can see the developmental stages of the ECG machine was
quite amazing, as were the individuals responsible for its development.
Additional ECG Historical Trivia:
Einthoven introduced the standard limb leads, I,II,& III or "derivations" as he called them in
1906. The labeling of the ECG complex: P,Q,R,S,T was introduced by Einthoven in 1895. In
his system, the largest deflection was labeled "R" wave, regardless of whether it was positive or not.