High-frequency therapy

The main active factor of all high-frequency therapy methods is considered to be alternating current, which is either directly supplied to the patient’s body (darsonvalization, ultratonotherapy), or occurs in the tissues and environments of the body under the influence of alternating high-frequency electromagnetic fields or their components (i.e. electric and magnetic fields) of high, ultra-high and super-high frequency.

Electromagnetic waves with a wavelength of 0.05 mm to 10,000 m (frequency less than 6x1012 Hz) are called radio waves (radio waves are known to be used for wireless transmission of information over long distances). Thus, high-frequency therapy can be called radio wave therapy. Classification of methods using high-frequency currents and electromagnetic fields based on spectral characteristics.

The physiological and therapeutic effect of high-frequency oscillations is based on their interaction with charged particles of biological tissues, which include not only ions, but also proteins, low-molecular metabolites, polar heads of phospholipids, and nucleic acids. Since the above-mentioned charged molecules have different sizes, their movement will occur at different resonant frequencies.

When high-frequency fields are applied, free current carriers, which in living tissues are ions, oscillate and collide. This effect underlies conduction current. A molecule can be neutral, but at the same time there will be charges at its ends (they simply add up to zero). Such a molecule, called a dipole, will rotate in an alternating field, which also leads to heat release. The amount of heat generated depends on both the parameters of the acting factor (current intensity, its frequency) and the electrical properties of the tissues themselves. Therefore, high-frequency therapy is selective.

In practice, this means that by changing the frequency, it is possible to achieve selective heating of certain tissues. Since tissue heating is caused by the absorption of certain resonant frequencies, it is carried out from the inside, and the sensitive sensors located on the skin do not feel the heat. An increase in tissue temperature is accompanied by hyperemia, increased permeability of histohematic barriers and microcirculation, as well as stimulation of metabolic processes.

Ultratonotherapy is widely and successfully used in dermatology and cosmetology for the treatment of: diathesis, eczema, neurodermatitis, acne, furuncles, for the removal of warts, postoperative scars and skin damage. The effectiveness of treatment is increased by preliminary application of medicinal or cosmetic products.

Darsonvalization is a method of electrotherapy based on the use of alternating pulsed current of high frequency (50–110 kHz), high voltage (up to 25 kV) and low power (up to 0.02 mA), modulated by short pulses (50–100 μs) of a bell-shaped form with a modulation frequency of 50 Hz. The method was proposed in 1892 by the French physiologist and physicist J.-A. d'Arsonval, after whom it was named. The active factor is an electric discharge arising between the electrodes and the patient's body.

The intensity of the discharge can be changed from "quiet" to spark. During darsonvalization, under the influence of discharges, ozone and nitrogen oxides are formed in small quantities, which are associated with a bacteriostatic and bactericidal effect. Unlike ultratonotherapy, during darsonvalization, due to the low current strength and the pulsed nature of the effect, in which pauses significantly exceed the time of impulses, the thermal effect is almost absent.

Darsonvalization is used mainly for local procedures.

Under the influence of d'Arsonval currents, the sensitivity thresholds of skin receptors (pain, tactile, temperature, etc.) to external stimuli increase. Numerous signals are sent from the receptors of the affected area to the central nervous system and its vegetative centers, resulting in a reduction or cessation of pain, itching, and paresthesia.

Local darsonvalization, in addition, increases skin turgor and elasticity, stimulates proliferative activity of germ cells of the hair follicle, enhances hair growth, prevents the development of wrinkles and hair loss. The beneficial effect of darsonvalization on the skin condition explains its wide popularity in dermatology and cosmetology.

Inductothermy (syn.: short-wave diathermy, short-wave therapy) is a method of electrotherapy, which consists of the effect on certain areas of the patient's body of a high-frequency (usually 13.56 MHz) alternating magnetic field. In this method, a high-frequency current flows through a cable or spiral (inductor) located on the patient's body, resulting in the formation of an alternating magnetic field. This field induces chaotic eddy currents (Foucault currents) in conductors, which are mainly liquid media (blood, lymph), as well as well-perfused tissues (muscles).

Eddy currents heat tissues from the inside, increasing their temperature by 2–5 °C at a depth of 8–12 cm. The main factor that has a therapeutic effect in inductothermy is heat, and the effect of this heat is significantly stronger than that of heat supplied from outside. In inductothermy, heat is generated deep in the tissues, mainly in the muscles, thereby significantly reducing the effectiveness of thermoregulatory mechanisms, most of whose receptors are located in the superficial tissues.

As a result of the increase in tissue temperature, blood vessels expand, lymph and blood circulation increases, the number of functioning capillaries increases, a slight decrease in arterial pressure is observed, blood supply to internal organs in the affected area improves, and the formation of arterial collaterals and anastomoses in the microcirculatory bed accelerates. Inductothermy has a positive effect on immunity: antibody synthesis is stimulated, the content of humoral immunity components in the blood increases, the phagocytic activity of leukocytes and macrophages increases, and fibroblasts are activated.

Inductothermy can be combined with medicinal electrophoresis (this method is called inductothermoelectrophoresis), which will ensure deeper penetration of drugs and in greater quantities.

Ultra-high-frequency therapy (UHF therapy) is the effect of the electric component of an alternating (continuous or pulsed) electromagnetic field of ultra-high frequency (from 30 to 300 MHz). With continuous oscillations, a significant contribution is made by thermal effects, the magnitude of which is determined by the average power of the field (Fig. II-2-6). In the pulsed mode of electric field generation, the thermal effects are small, since pauses are a thousand times longer than the pulse duration. Thus, the pulsed mode serves to enhance the specificity of the effect of the electromagnetic field on molecules.

Microwave therapy (ultra-high-frequency electrotherapy, UHF therapy) involves the use of electromagnetic waves of the decimeter (from 1 m to 10 cm; decimeter-wave (UHF) therapy) and centimeter (from 10 cm to 1 cm; centimeter-wave (CMV) therapy) ranges. Microwaves occupy an intermediate position between electromagnetic waves of the ultra-high-frequency range and infrared rays. Therefore, in some of their physical properties they are close to light energy.

When microwaves are reflected, especially by tissues with different electrical conductivity, the incoming and reflected energy can add up, which forms so-called "standing waves" that create a threat of local tissue overheating, such as the subcutaneous fat layer. Part of the microwave energy absorbed by the tissues is converted into heat and has a thermal effect.

Along with this, there is also a specific oscillatory effect. It is associated with the resonant absorption of electromagnetic energy, since the frequency of oscillations of a number of biological molecules (amino acids, polypeptides, water) is close to the frequency range of microwaves. As a result, under the influence of microwaves, the activity of various biochemical processes increases, and biologically active substances (serotonin, histamine, etc.) are formed.

In the physiological effect of microwave action, two types of reactions are distinguished: local, caused mainly by local heating of tissues, and neurohumoral as a manifestation of adaptive-adaptive reactions. Maximum heat generation occurs during SMV therapy in the skin and subcutaneous fat, where the temperature can rise by 2-5 °C. During UHF therapy, mainly water-rich tissues are heated, where the temperature can increase by 4-6 °C with comparatively low heating of subcutaneous fat.

Local heating leads to dilation of blood vessels, increased blood flow, decreased smooth muscle spasm, which helps eliminate congestion and reduce swelling. The analgesic and antipruritic effect of microwaves is associated to a greater extent with the reduction of swelling and the elimination of ischemia. Microwave therapy also has an anti-inflammatory, antispasmodic, hyposensitizing effect. Microwave therapy is indicated for inflammatory skin diseases (furuncles, carbuncles, hidradenitis, trophic ulcers, postoperative infiltrates).

Millimeter (MMW therapy), or extremely high-frequency (UHF therapy) therapy is based on the use of electromagnetic waves of the millimeter range (frequency from 30 to 300 GHz, wavelength - from 10 to 1 mm). UHF therapy is a relatively new physiotherapeutic method introduced into medical practice on the initiative of Academician of the Russian Academy of Sciences N.D. Devyatkov, who was one of the first to draw attention to the unusual biophysical properties of millimeter waves.

Millimeter waves are well absorbed by tissues, especially those rich in water, or by various hydrated molecules and supramolecular structures. As a result, unlike decimeter and centimeter waves, millimeter waves have low penetrating ability into the body (up to 1 mm), due to which the primary effect of this factor is exclusively local.

In the skin, millimeter waves are capable of inducing conformational changes in various structural elements, primarily in receptors, nerve conductors, and mast cells. Therefore, in UHF therapy, preference is given to effects on reflexogenic zones and acupuncture points.

During UHF therapy, activation of the body's antioxidant system is observed, blocking the processes of lipid peroxidation, which play a key role in damage to cell membranes.

The greatest positive effect of UHF therapy in dermatology has been recorded in the treatment of long-term non-healing wounds, bedsores, trophic ulcers, and allergic dermatoses.

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