z IONTOPHORETIC BURN-PROTECTION METHOD AND APPARATUS
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TECHNICAL FIELD
This invention pertains to plural electrodes for application to living subJect having skin, to accomplish effects related to the passage of electric current.
BACKGROUND OF THE PRIOR ART
Around the turn of the ~entury the art disclosed a plethora of electrode ty~es for applylng "electric treatments" to the human body. The elctrodes were normally placed upon the body in relation to the position of an organ to be treated.
These l'electric treatments" encompassed a wide range of appllcations. ~or example, galvanic (direct current) treatments have been popular in the past for their polar effects on ionized molecules, causlng the lonized molecules to be driven through the skin, usually superficially This phenomenon is known as iontophore-sis or ion transfer, and it has been employed for the introduction of medicants3 or even simply moistur~, into the skin of a patient.
More specifically, some ions of zinc and copper can be employed in the treatment of some skin infectionsg and chlorine ions have been employed for the loosening of superficial scars. FurtherJ vasodilating drugs can be used in rheumatic and peripheral vascular affections, and skin anesthesia can be produced by iontophoresis o~ local anesthetlc drugs. It has been suggested that application of direct current to carefully selected areas of a living anlmal can produce anesthetic ef~ects.
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University Park Press).
In generalg the electrodes were disclosed merely as structures and were not related to any unde-sirable side-effects the electric current might have upon the skin. An example is the U S. Patenk No.
562g7655 issued in 18953 to Hortong Jr. The usual ob~ec-tive was merely to decrease the contact resistance to the skin.
F. Levitt ln "Archives of Dermatology"g Vol. 98 No. 5, November 1968, reports on pps. 505-7 the produc-tion of long-term anhidrosis by electric treatment of the feetg or hands. However, he disclosed only the use Or "a two inch square of sheet lead" as an electrode.
This is "placed ln a shallow pan containing enough water to ~us-t cover the palm or soles'ig there being one elec-~rode and one pan f`or each palm or sole. IIls test results indicate that the treatment inhibits perspira-tion (sweat) where the electric current is provided.
Although the above-melltioned iontophoretic treatments have been ~ound to be effective, using known electrodes in these direct current applications fre-quently results in iontophoretic burns to the patient, generally at the negative electrode. These burns are not caused by elevated temperature but by a spontaneous ef~ect o~ the electrlc current on the skin. These burns require a relatively long time to healg and can result in formation of unsightly and highly undesirable scar tissue.
A paper by Leeming and Howland in the "~ournal o~ the American Medical Association"g Vol. 214g NoO 9g Nov. 30, 1970g recites instances of burns but does not present means for preventing such trauma. This unde-sirable effect of iontophoretic treatment has resulted in a less than enthusiastic reception of iontophoretic techniques by the medical community in spite o~ the great and varied advantages to be realized through their use and development.
Accordinglyg there has existed a need for a .~, 8~52 convenient and e~fective method and apparatus for pre venting iontopheric burns during the application o~
electrical energy to the skin of a human body. As will become apparent from the following~ the present inven-tion satisfies that need.
BRIEF SUMMARY OF THE INVENTION
A method and apparatus ~or applying electricalenergy topically to the skin of the human body is pro-vided by which undeslred side-effects are greatly mini-mized and may be eliminated.
The electrode configuration o~ the inventionincludes two conductive areas to which opposite polariky of electric current is supplied and wh~ch may be rela-tively adjacent. When the electrodes are ad~acent the 15 electric current does not pass through or near electro~
sensitive organsJ such as the heart.
Although the present method and apparatus for preventing iontophoretic burns will be described as used in connection with an ele~trical treatment for lnhibiting perspiration, it will be understood that this method and apparatus is equally well suited for use with other electrical treatments, such as the examples de-scribed above.
One side-effect that is substantially elimin-25 ated by the electrode structure o~ thls inventlon is the iontophoretic burn. This is because of the inter-position o~ relatlvely thick porous and pre~erably moistened material between the negative electrode and the skin.
Another side-effect that is reduced is pain or tingling due to the passage of current. This is brought about by increasing the area of the positive electrode.
An alternate embodiment utili~es intermingled nagative and positive electrodes of small size, all 35 having porous material.
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~3~-In accordance with one broad aspect, the invention relates to an electrode structure for apply-ing an essentially unidirectional electric current through the skin of a living bodyr comprising: a first electricall~ conductive electrode having a porous material with a thickness of at least thxee millimeters upon one side thereof adapted to be interposed between said electrode and said skin' a second electrically conductive electrode adapted to contact said skin at a location thereon spaced from said first electrodeS a controlled source of unidirectional electric current having a positive pole and a negative pole~ and means for connect-ing said first electrode to said negative pole and said second electrode to said positive pole, whereby ionto-phoretic burn is minimized.
BRIEF `PESCRIPTION OF THE PR~WINGS
FIGURE 1 is a sectional elevation, at 1-1 in F~G. 2, of a conductive electrode, the porous intervenor, and the skin to be treated.
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FIG. 2 is an lllustrative plan view o~ a pair o~ electrodes and of the remainder o~ the system.
FIG 3 is an alternate embodlment in which one electrode is larger than the other.
FIG. 4 is another alternate embodiment in which positive and negative electrodes o~ small size are spatially intermingled.
FIG. 5 is another alternate embodiment in which positive and negative electrodes o~ small size are sp~tially intermingled, with the positive electrodes larger than the negative electrodes.
DEl'AILED DESCRIPTION OF THE INVENTION
In FIG. 1 numeral 1 indicates a conductive electrode. This may be ~lexible or rigid and is typi-cal~y ~abrlcated of metal, of which stalnless steel and alu~inum are examples.
The skin is represented by epidermis 2. This h~s been simply shown. The physiolo~ical detail o~ the epidermis is shown in a drawing on page 8~o~ Vol. 16, 15th Editionj c~pyright 1974J of the "Encyclopedia Britannica".
Porous intervenor mate;rial 4 is typically in loose electrical contact to the underside of electrode 1 so that it can be changed and discarded a~ter each use.
A suitable material ~ is a type of felt thatcan b~ obtained commercially. While the thickness stipulated as principal in this invention is not com-monly available, it can be obtained in special order. A
3 quallty control speci~ication for this material is that it be ~ree of tramp metal.
A thickness greater than 3 millimeters may be chosen if a greater value of the current times the time-of-treatment factor is desired.
Flexible electrical conductor 5 is conductively connected to electrode 1. Electrode`l may take the form of a snap ~astener as well as a metallic plate or a conductive plastic such as silicone. Two examples o~
electrode arrangements are illustrated in ~IGS. 2 and 3.
~5--~n the view of FIG. 2 the negative electrode 1 is seen.
Porous material ~ is underneath the same.
Second electrode 5 is shown adjacent to elec-trode 1, with a separation between the tl~o of the order of a fraction of one to a few centimeters9 typi-cally. Positive electrode 6g connected by conductor 7 to a source 8 of electric current, may be a simple metallic electrode, with or without the thick porous intervenor 4.
Source 8 may be merely a source of di~ect cur-rent9 such as a batteryO The current normally required is within the range of from a fraction of a milliampere to twenty milliamperesO A known adjustable resistor may be included within source ~ to allow the user to obtain the proper current for any process.
For inhibiting perspiration a current density on the positive electrode of from 1/20 to perhaps 1/2 milliampere per square cent-lmeter is desired. Natural-1~, the actual current density and treatment duration employed in any of the above-mentioned applications o~
this inven~ion should be chosen to accommodate the particular case at hand. Accordingly, the actual values mentioned herein are offered as an example of one of the treatments whlch can employ the method and apparatus of this invention.
Source 8 may also be a known "constant current source''g ~laving the same specifications as above and a control to allow the user to select the desired constant value of current. Another feature of a suggested unit would limit the maximum current that is applled.
The source of current may also have other forms, including unidirectional pulses or varying cur-rent, but not alternating current of commonly used frequencies, nor radio frequency current.
The arrangement of electrodes 1 and 6 may take many formsg depending upon the area that is to be treated and the choice of the designer. These elec-trodes may be attached to a non-conductive frameg which is shown dotted at 9 ln FIG. 2. This is convenient for .
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inhiblting perspiration on a hand or a foot.
Alternativelyg positive electrode 6 may be placed on the palm of a hand for inhibiting perspira-tion there9 and the negative electrode may be placed on the back of the hand, or on the wrist.
Conme~tive means 3 attach electrodes 1 and 6 to frame 9.
Of coursej the negative electrode may be placed elsewhere~ such as in combination with the positive electrode within gloves ~or a hand or hands. The posi-tive electrode is positioned to inhibit perspiration and the negatlve electrode is positioned ad~acently for the current return. Similar arrangements are possible in stockings ~or the feet. Nominal pressure between the electrodes and the skin can thereby be maintained in any position.
For inhibiting underarm perspiration the posi-tive electrode~ at least, can be curved to fit under the armpit. The negative electrode may be located nearby, or the positive and ne~,ative electrodes can each occupy one-half o~ the ax~.lla area, with an insu-lati.ve separator between.
In FIG. 3, elements 5~ 7 and 8 are as before.
However, positive electrode 10 has a relatively large 2F) area and negative electrode 1' has a relatively small area. The positive electrode is rectangular, rather than square~ as before. The elec~rode may have almost any shape when secondary consi~erat~ons so requlre.
The conflguration shown is useful for inhib~t-3 ing persplration of the hand. Electrode 10 is placedupon the palm of the hand and electrode 1' is placed upon the fingers ~ the same hand.
In the practice of perspiration i~hibition and similar treatments it has been found that iontophoretlc burn is associated with the means of the prior art at the current densltles re~uired to produce the desired result. Our investigation isolated ~he burn phenomenon to the negatlve electrode. In accordance with the present ~nvention, the metallic termlnal or plate of the 8~5;~
negative electrode is adequately covered with a thick felt padg and lontophoretic burns are thereby av~ided when a current time limitation is observed.
The nature o~ the thic~ ~elt electrode has been described. It :Is moistened ~or use by employing tap water. It has been found that distllled or deionlzed water may also be used.
In an illustrative example the palm o~ a hand was treated with a positive electrode having an area of 90 s~uare centimeters. The negative electrode con-tacted the ~ingers and had an area of 30 square centi-meters. The thickness o~ the ~elt was 6 millimeters.
A current of 15 milliamperes was allowable for a period of 10 minutes without an iontophoric burn occurring. Alternately, at 7.5 ma. the allowable treat-ment time was 20 minutes. At 3.7~ ma. the allowable time was 40 minutes.
It has been determined that there i~ some particle or substance that migrates from metallic elec-trode 1 through intervenor 4 as current is caused topass into skin 2. This particle or substance must not be allowed to fully migrate to the skin; ~or if it does, a burn results. Thus, the thickness ~ the in-tervenor acts as a transit barrier or delay to prevent the burn-causln~ particles ~rom reaching the ~in within the treatment period ~or a given current.
The intervenor cannot be conveniently reJu-venated, so as ~ practical matter the intervenors for the negative electrode are used as requlred for a treat-ment and then are disposed o~.
The presently preferred type of intervenormaterial 4 is composed of metal-~ree natural fibers of wool or cotton.
Other equivalent man-made ~iberous materials may be used, such as a synthetic o~ the viscose nylon or polyester type Alternatively, porous materials such as foams or sponges may be usedg and all of the reclted substances have been generally termed l'porous 1l .
While the lnhibition o~ persplration is `~
electrically inducedg the inhibition does not occur immediately a~ter treatment9 but after an interval o~
about two weeksg after which time one or two further treatments will inaugurate another six week period~ and so on.
The area of skin that is effectively treated also includes a leaching or spreading e~fect that e~tends beyond khe lmmediate area that is directly con-tacted by the electrodes.
By empirical means it has been determined that the spreading of the electric current per se is very small in relation tothe spreading of the inhibition of perspiration. It thererore appears that the inhibition is the result o~ a chemical effect that creates a keratin plug in each sweat duct.
Because of the spreading er~ect o~ the treat-ment to a limited area beyond the skin that ls contacted by the electrodesg the latter may be flat, without regard to undulation of the skin, as upon the palms of - 20 the hand or the soles of the feet. In prior electrode art it is believed that this spreading effect was not observed, or was not appreciate~, since all of the art that has been examined has not commented upon it.
The spacing between the pairs o~ electrodes in FIGS. 2 and 3 may be relatively close, so long as the current is prevented from going from one electrode to the other without passing through the skin; hence not accomplishing the method of thls invention.
To maximize safety and convenience to the user, 3 batterie~ ~ay be used for current source 8. The voltage required varies according to the total resistance o~
the load circuit. h voltage ~ 45 volts is typical.
A small battery having this total voltage is commer-cially available and is suitable, since the battery need only supply a current o~ a few milliamperes.
An advantage of the close-spaced electrodes in FIGS. 2 and 3 lles in the fact that the treatment current may be rapidly increased at the start of a kreatment without an undesired sensat~on to the user.
~ 52 It is desirable that the current be increased from zero or a low value at the start. Wlth close-spaced electrodes the current may be increased to treat-ment amplitude in a fraction o~ a second.
With a distally removed electrode having a spacing of many centimeters and perhaps attachment to another member o~ the body, the current must be increased slowly. A certain procedure is for a careful operator or the user to turn a current-controlling potentiometer very slowly and steadily so that pain and shock will be avoided. However, the distally removed electrode mode of treatment is equally effective in burn protection.
Unless close electrode spacing is employed the current must be slowly decreased at the end of the treat-ment.
Although inhibition of perspiration was con-sidered primarily accomplished at the positive electrode~
inhibition to a lesser degree ls accomplished at the negative electrode.
A basic period of treatment for anhidrosis, the inhibition o~ perspiration" is ~orty minutes.
InitiallyJ six treatments are ~riven, preferably one every other day.
Extensive preparation of the s}cin before the electric treatments is not required. However, in order to assure conslstent results i~, is desirable to s~ab the ~kin where the electrodes are to be applied with rubbing alcohol.
An opposite alternate skructure to the distal arrangement of electrodes is that shown in FIG. 4.
Here, small positive electrodes 14 and negative elec-trodes 15 are intermlngled, being typically about one square centimeter in size and separated ~y a few milli-meters one from the other. All are provided with a ~elt-like layer between the electrode proper and the skin. A system of conductors 16 for the-positive and 17 for the negative electrodes which do not touch the skin connects all electrodes to current source 8.
- Also, this type o~ intermingled structure may c~
have the positive electrode 18 of larger area than that of the negative electrode 19, as shown in FIG. 5. The other aspects are the same as in FI~
~hen the posit~ve electrode is made larger in area than that of the negatlve electrode in any of the embodimentsg there -ls a ~mit to the difference in areas allowable in practice. This is about three-to-oneg as evidenced by the 90 sq. cm. positive area and the 30 sq. cm. negative area electrodes in the embodiment of FIG. 3.
For simultaneous anti-perspiration treatment of two hands or two feetg two sets of electrodes accord-ing to FTG. 3 may be connected to a constant current source 8. ~Ioweverg we elect to use independent con-stant current sources9 each powered by its own battery.This allows greater current ~or one hand than the other to compensate for possible dif~erent sensitlvities of each hand.