Lecture VI Dr. Amal HM.
Ibrahim Professor of Physical Therapy
aebrahim123@hotmail.com
Direct current (DC) is a unidirectional
flow of electrons through a conductor for 1 sec or longer or current passing continuously in the same direction with the same intensity. It is known as galvanic current or constant current
aebrahim123@hotmail.com
aebrahim123@hotmail.com
The current can be modulated by
three means first, reversed DC in which the current flow for 1 sec or more in one direction then reversed for 1sec or more.
aebrahim123@hotmail.com
Second, interrupted DC, in which the
current is flow for 1 sec up to 60 sec, the current switch off for some seconds and then starts again. This type is used to cause twitch contraction of denervated muscles.
aebrahim123@hotmail.com
Third modulation is surged DC or ramping
DC in which the current is rising gradually and falling gradually over 1 second or longer, the term ramp up and ramp down are used respectively.
aebrahim123@hotmail.com
Direct current passes to the
tissues through two electrodes covered with wet pads, wet sponge, water bath or bath with suitable solution. The DC current will changed to convection current in the wet pads and tissues.
aebrahim123@hotmail.com
At positive electrode (anode), an acid is
formed and at the negative electrode (cathode) an alkaline is formed causing chemical damage or burn. The magnitude of chemical damage depends on current density (the current intensity per unit area) and time of application.
aebrahim123@hotmail.com
The current in any circuit is directly
proportional to the voltage and inversely proportional to the resistance. The major resistance facing any current applied to the tissues is the epidermis (impedance of the skin).
aebrahim123@hotmail.com
Direct current has been used for a period
of 10 to 30 minutes. The current density must be kept at the level that does not cause tissue damage or discomfort to the patient. Commonly the range of dose is between 0.33mA/cm and 0.5mA/cm.
aebrahim123@hotmail.com
1- Sensory irritation and hyperemia
Direct current causes mild tingling or
prickling sensation. More current leading to erythema of the skin under the electrodes (the effect is marked under the cathode, negative electrode).
aebrahim123@hotmail.com
2- Sedation and relief pain
Direct current is thought to reduce
nerve conduction velocity by using low dosage as 0.3mA for a long period, about 30 minutes. Also DC can relief pain through inhibition of pain receptors through pain gate theory.
aebrahim123@hotmail.com
3- Enhance wound healing
Application of DC current for 2 hours three times
daily accelerates healing of various kinds of wounds. First put the negative electrode (cathode) over the wound for 3 days and the positive electrode (anode) about 25 cm away from the wound. The total current used could be varied between 0.2 and 1mA, so the current density for most ulcers would be very low.
aebrahim123@hotmail.com
3- Enhance wound healing
The mechanism by DC suggested that an antibacterial
effect accelerate healing, increased circulation and the growth and repair may account for.
aebrahim123@hotmail.com
Factors affecting healing Factors known to delay healing are divided into general and local: 1- General: age, protein deficiency, low vitamin C level, steroids and NSAIDs (inhibitory effect), temperature (lower healing rate when colder).
aebrahim123@hotmail.com
Factors affecting healing Factors known to delay healing are divided into general and local: 2- Local: poor blood supply/ ischemia, adhesion to bone or other underlying tissues, continued inflammation, drying of the wound, excessive movements.
aebrahim123@hotmail.com
4- Tissue destruction It is the caustic effect of DC current applied through a fine needle (cathode) as active electrode leading to liquefaction and a large moist pad (anode) as dispersive electrode lead to coagulation of proteins. This effect is used in destruction of unwanted tissues as warts or removal of unwanted hair.
aebrahim123@hotmail.com
5- Anodal galvanism (Electrophoresis)
Electrophoresis is the using of
anodal galvanism for treatment of local edema (drying effect)
aebrahim123@hotmail.com
6- Electrotonus
Application of sub-
threshold nerve stimulus does not cause action potential but it affects their membrane potential. The negative electrode (cathode) causes local depolarization. The positive electrode (anode) causes the reverse-hyperpolarization.
aebrahim123@hotmail.com
7- Iontophoresis Iontophoresis is the use of direct current to driving topically applied substances in the form of ions across biological membrane for therapeutic purposes.
aebrahim123@hotmail.com
When DC used for pain relief the
recommended dosage differ according to the polarity used. When use cathode (active electrode), the current density used between 0.5-0.8mA/cm2 for 10-20 minutes. If the anode is used (active electrode), lower current density between 0.15-o.25mA/cm2 for 15-30 minutes.
aebrahim123@hotmail.com
1. Chemical burn or damage of the treated tissues as a result of high current density, low skin resistance (presence of cuts abrasions or uneven pressure), and touch of metal part of electrode to the skin. 2. Shock can occur if the circuit is broken suddenly.
aebrahim123@hotmail.com
Iontophoresis is a specific therapy by
using direct current to introduce ionized drugs across biological membrane for therapeutic purposes. It is sometimes called ion transfer.
aebrahim123@hotmail.com
aebrahim123@hotmail.com
If a direct current is applied to the
electrolyte, convection current will flow. The positive charged ions will move toward the anode electrode. The drug must be in ionic form (has a charge) it can be travel in either direction depending on the polarity applied.
aebrahim123@hotmail.com
The tissues are continuous electrolyte with the
solution of the wet pad or sponge which contain the ionized drug. The negative charged ions will drift away from the negative electrode and pass through the skin and into the tissues and the same will happen to the positive charged ions.
aebrahim123@hotmail.com
The effects of Iontophoresis are either local
in the skin (under active electrode) or systemic by disseminated through the tissue fluids.
aebrahim123@hotmail.com
The effects of Iontophoresis depend on: 1- Current density which is limited by patient
tolerance (should not exceed 0.2mA/cm+). 2- Time of application (20 to 30 minutes). 3- The concentration of ions in the solution between 1 to 2%.
aebrahim123@hotmail.com
The effects of Iontophoresis depend on:
4- Presence of some ions like zinc or silver form precipitates
which are insoluble and may limit penetration. The effect of Iontophoresis therapy depends also on the medication to be introduced. The therapist should be fully informed of the effect, side effect, indications and contraindications of applied medications before treatment begins.
aebrahim123@hotmail.com
1- Local Anesthesia
Using drugs like lignocaine or procaine will cause local coetaneous anesthesia for about 14.5 minutes, increased if we add adrenaline, (infiltration cause anesthesia about 22.2min and topical application about 2.1 min). Local anesthesia has been used therapeutically in the treatment of herpes zoster and trigeminal neuralgia. Sometimes used in physiotherapy department and with patient who are sensitive to hypodermic injections for ear and eye surgery.
aebrahim123@hotmail.com
2- Treatment of idiopathic hyperhidrosis (excessive
sweating)
Glycopyronium bromide administered by Iontophoresis has
been recommended as simple, safe and effective treatment of excessive sweating. Hyperhidrosis usually affects palms, soles and axilla whose exocrine glands innervated by sympathetic system. The effect of Glycopyronium bromide (anticholinergic agent), lasts a variable length of time. Abed and Morgan 1974, found a mean of 33.7 days for the palm and 47.2 days for the soles of foot. It was suggested that few patients need repeated treatment every 4 to 6 weeks
aebrahim123@hotmail.com
aebrahim123@hotmail.com
3- Application of vasodilators Histamine is a vasodilator has been administered by Iontophoresis for a variety of disorders. Histamine Iontophoresis is used for arthritis, enhance wound healing and improve the viability of skin grafts.
aebrahim123@hotmail.com
4- Application of inorganic cations
Inorganic cations carry a positive charge and are
delivered from the anode. Zinc has been used in the treatment of patients with ischemic ulcers to promote healing and prevent infection. Silver Iontophoresis has also been used with some success in the treatment of patients with rheumatoid arthritis. Copper Iontophoresis has been used to treat chronic fungal infections of the feet. Magnesium Iontophoresis has been used to treat patients with sub deltoid bursitis.
aebrahim123@hotmail.com
5- Application of inorganic anions Inorganic anions are administered under the cathode. Acetic acid Iontophoresis has been described the treatment of patient with calcium deposits around the shoulder and myositis ossificans affecting quadriceps femoris muscle. Iodide iontophoresis has been used as useful in the management of problems related to scar tissue and release of scar adhesion of tendon to bone.
aebrahim123@hotmail.com
6- Application of antibiotics Application of antibiotics by iontophoresis has been used for treatment of ear chondritis following burn injury and non healing ulcers.
aebrahim123@hotmail.com
7-Application of anti-inflammatory drugs Iontophoresis has been used to treat tendonitis and bursitis. The advantages of these methods are pain less and sterility of the treatment. The disadvantages are being very expensive and time consuming.
aebrahim123@hotmail.com
8- Relief of chronic pain (neurogenic pain) Iontophoresis has been used and recommended for the treatment of chronic pain syndromes, like patient suffering from post-herpetic neuralgia and chronic pain in terminal cancer.
aebrahim123@hotmail.com
In addition to the general principles of application
Ensure the drug is under the correct electrode (positive charged ions under anode and negative charged ions under cathode). Most of ions used are positive except acetate, chloride, iodide and salicylate which are negatively charged.
aebrahim123@hotmail.com
The treatment time and dose is variable, that if the effect of treatment is inadequate you can continue for longer time. The initial dose for hyperhidrosis should be low: 1.125mA for 3min for a 30cm2. For other iontophoretic treatment the dosage is about 0.05mA/cm2 for 20 to 30min.
aebrahim123@hotmail.com
Systemic effects can occur, especially with large areas
application, in form of headaches, abdominal pain, or mild dryness of the mouth.
aebrahim123@hotmail.com
1. Pregnancy. 2. Cardiovascular disorders especially with histamine
iontophoresis.
aebrahim123@hotmail.com
The circuit must be closed. The dispersive electrode must be larger 2.5 than the active electrode for muscle and nerve stimulation. The both electrodes are equal in size for sensory stimulation. .
aebrahim123@hotmail.co
The dispersive electrode (indifferent or
inactive) should preferably be positioned opposite to the active electrode, or at a distance about 25cm away from active electrode.
aebrahim123@hotmail.co
Cover the electrodes with pads of
lint, gauze or sponge. The electrode is slightly smaller 1cm than the pad to avoid electrode skin touch. The pads must be thick enough (about 1cm after compression). .
aebrahim123@hotmail.com
Good fixation of the electrodes using bandage for irregular skin surface to avoid higher resistance of some points. Prefer to treat extremities by immersing in water bath.
aebrahim123@hotmail.com
Explain the nature of treatment and feeling to the patient. Decrease skin resistance by wetting, warming, or washing the skin. Increase intensity slowly and dont switch on or off with switch above zero. Avoid electrical stimulation over areas with low resistance like cuts and abrasions to avoid uneven skin resistance.
aebrahim123@hotmail.co
Practical application of direct current
In addition to the general principles of application
Prepare the patient, examine and test the treated area. Warn the patient to report any painful sensation to avoid the risk of chemical burn. Avoid application over cuts and abrasions to avoid chemical burn.
aebrahim123@hotmail.com
Practical application of direct current
If a water bath is used for extremities, the
electrodes clipped to the side of the container. The size of this electrode does not matter but it should be situated well away from the immersed part. If one electrode is used in the bath it called monopolar bath and if both electrodes are used it called bipolar bath.
aebrahim123@hotmail.com
Practical application of direct current
Warn patient not to give his limb away from the
bath during treatment to avoid shock. Cover the untreated area close to the surface of the water by cream or oil to avoid the passing of current through the tissues and cause burning sensation.
aebrahim123@hotmail.com
Practical application of direct current
The meter may show sudden little increase
without the control being move due to lowering of the skin resistance. You should turn the control down slowly and examine the area to avoid chemical burn.
aebrahim123@hotmail.com
Practical application of direct current
For enhance wound healing, measure the wound
size (by transparent) to calculate the current density and to evaluate the rate of healing. The ulcer may be packed with gauze soaked in sterile saline to allow adequate conduction of the current. The electrodes wrapped in saline soaked gauze and fixed to the wound by strap or bandage.
aebrahim123@hotmail.com
Practical application of direct current
Apply the cathode as active electrode for the first
three days for its bacterio-cidal effect if the wound is infected and the anode should be of the same size or larger than cathode and placed on the nearest area. After three days we use anode as active electrode and cathode as dispersive electrode. If the wound is not infected we start treatment with anode as active electrode. The current should not cause muscle contraction and might applied each day for 2-4 hours.
aebrahim123@hotmail.com
