What makes the
physiotherapeutists when they practise a treatment of
electrotherapy?
Which is our goal?
Our objective is to
apply a current, by means of electrodes, in the body
of the patient and this through the skin.
This banal question
can seem alleviating. It is perhaps significant to
visualize the whole operations well :
- We install the
patient.
- We position a
first electrode on the skin.
- Then a second
on another place of the skin.
- We connect the
first electrode to the generator.
- Then the
second.
- We
parameterize the generator.
- The treatment
is launched.
- The power is
on by a wire.
- Then through
the first electrode.
- Then through
the skin.
- In the tissues
of the patient.
- Arises by the
skin.
- With through
the second electrode.
- And finally by
the second wire, to the generator.
Out we let us know
that the various crossed elements have resistances,
different impedances;
- The wire is
purely resistive and of low resistance and
negligible.
- The electrode
is practically resistive and of low
resistance, fixed.
- The skin is
strongly capacitive, its resistance is
variable.
- The crossed
tissues are purely resistive and of low
resistance, fixed.
- The skin is
strongly capacitive, its resistance is
variable.
- The electrode
is practically resistive and of low
resistance, fixed.
- The wire is
purely resistive and of low resistance and
negligible.
If we want to be
rather precise, it is necessary to take account of 5
impedances. We limited our approach to this form:
This
system is simplified too much to understand how is
distributed the current in the various elements.
This
system is however in conformity with our observations ;
- The impedance is maximum for
the D.C. current.
- It decreases with the
frequency, to arrive at a minimum.
