In 1906 the Dutch physiologist Willem Eithoven, invented
a method to register the feeble voltages that occur among
differents areas of the human body, by means of a string galvanometer.
For his researches he was granted with the medicine Nobel
award in 1924. To improve the testing accuracy, later on the
string galvanometer was replaced by a more sensitive apparatus,
the loop galvanometer, in such away the voltages of the cardiac
muscle generated in the skin surface could be measured and
recorded in graphics as kown as cardiogram allowing to observe
the heart functioning status. Certainly such new discoveries
gave birth to the electrocardiography.
Thus the electrocardigraph became an invaluable tool to
undertand of heart diseases since by a carefull studying of
the recorded cardiogram for a few hours at an early stage,
it was possible now that a heart attack could be prevented
by mean of a more accurated technique the vector cardiogram.
|Fig. 352 ilustração do
novo campo da ciência médica, a eletro medicina.
It consists in the use of an oscilloscope, which offers the
possibility to show in a panoramic overview the several voltages
generated by the heart muscle, thus allowing the physician
to be able in evaluating their interrelationships.
Soon the technique developed by Einthoven was used for the
measurement of even lower voltages, about 30 microvolts, which
were generated by the brain detected in several areas of the
surface of the skull. In this way through the encephalograms
the physician could be able to study the behavior the the
brain, which was a step forward in the science of neurology.In
spite of the aforementioned techniques around 1950 several
other types of electronics aids for medical diagnosis were
availabe for a detailed study of the human body. Thus sensitive
photocells used in advanced types of colorimeters allow accurated
biochemical analysis for many components fgound in the blood
stream such as uric acid, hemoglobin and creatine, fig 352.
The classical medical diagnosis methods by auscultation and
percussion were replaced by advanced and precise cliynic techniques.
Among them are: diathermy, myography and ultrasonic procedures
as well as including an array of patiente computer controlled
monitoring electronic devices. Table 4.
|TABLE 4 – SEVERAL TYPES OF CURRENTS
USED FOR ELECTROTHERAPEUTICS PURPOSE IN THE LATER FORTIES.
||Galvanic current is simply D.C. up to
75 V at 1 to 20 mA.. It is obteined from batteries, D.C
power lines, or most commonly from A.C. lines using selenium
or vlave rectifiers. It is used for treatment of certain
types of painflu inflammations and iontoforesis.
| PULSANTING GALVANIC
||Similar to the aforementioned, whose pulses are are
produced by electromechanical devices, for instances such
types of relays. It has the same electrotherapeutics as
the Galvanic current.
||It is a a D.C. current whose amplitude is varied periodically
by motor-driven variable resistors, Thyratron valves.
||This modality is similar to the pulsating Galvanic,
except for a slight negative dip, a sharp positive peak,
and higher frequency 1 to 2000 Hz. Its amplitude is about
75 Volt at maximum 1 mA. It is produced by Faradic generators
or coils, sometimes called inductoriums. It is used to
stimulate injured muscles as well as muscles whose nerves
are receovering from diseases or injury.
||It is a low-frequency Galvanic current – 5 to
30 Hz produced by electro-mechanical generators or generators
operating with Thyratron valves. It is used to stimulate
||It has the same voltaga and current as in the Galvanic
type whose 60 Hz frequency is surged by a thermally aactuated
interrupter or a motor-driven generator. Such type of
current is used in the electric shock terapy.
||Static waves are generated by high-voltage rotating
friction machines, but a very small current around 1 mA.
Due to its complexity has few practical applicatin in