What is Diathermy – Generalities, SWD (Short Wave Diathermy) Description.

G. Guido Rodriguez PT – RT, About this author…

I have been asked “What is Diathermy?” multiple times in my practice and it is always a pleasure to answer it, so here are the details of what diathermy is.

The word “Diathermy” comes from the Greek “Dia” (through) + “Thermé” (Heat), “Heating Through.” 

It is deep heat in the tissues produced either by electrical currents (low tension with high amperage), high-frequency electromagnetic radiation (Microwave, Short Wave, ultrashort wave).

The increase of temperature and other physiological changes are achieved by the resistance of the tissues to the passage of the mentioned currents /radiations, and it can also include ultrasonic waves.

The tissues can be warmed, heated o cauterized by the utilization of these methods which the main difference is their range and frequencies of wavelengths as well as penetration capability.


But, how, high-frequency electromagnetic radiation can produce heat in body tissues? 

OK, let me give you a better picture of it.

In a typical home, the standard wall power outlet voltage in the USA is 110 Volts – 60 Hz, AC (alternating current).

An alternating current is where the current oscillates in “waves” being positive (+) and then negative ( – ); and in a wall outlet the frequency of 60 Hz (60 times per second).


So, if you happened to put your fingers in a power outlet the free ions in your tissues are going to be agitated.

The electrical shock will shake you 60 times per second as the current passes through your body.

But, If that frequency is increased like in the Short Wave Diathermy that operates at  27.12 MHz (27,120,000 times per second), being close exposed to that electromagnetic radiation,  the faster the ions move or oscillate, the more thermal energy they produce, transforming kinetic energy into thermal energy.


What types of Diathermy exist then?

Thera are in fact five types of Diathermies;

  • Medical Diathermy: it is the application of currents of low voltage and high amperage which produces warmth in deeper tissues and is commonly used to promote muscle relaxation.
  • Short Wave Diathermy (SWD): oscillating electromagnetic fields of high frequency (2.7 Mhz), it heats to a tissue depth of 3-5 cm, it is commonly used in Physical Therapy and Occupational Therapy. SWD can be administered in continuous mode for thermal effects or pulsed for minimal or non-thermal
  • Microwave Diathermy: (Yes, the same energy that utilizes the microwave in your kitchen) it heats to a greater tissue depth than SWD, and in your microwave, as you know, it heats your food from the inside out.
  • Surgical Diathermy: During a surgical procedure it is used for electrocoagulation, cauterizing vessels to prevent bleeding.
  • Ultrasound diathermy: in this case, it is not an electromagnetic radiation, it heats up deep tissue via sonic agitation using an ultrasound head or transductor. It penetrates 5- 6 cm, but unlike SWD it does not heat up all the tissues, only soft tissues.


The Utilization of Short Wave in Physical Medicine and Rehabilitation


I would like to focus now, on a complete heating method for tissues, it is utilized locally, for deep heat up to 5 cm, (a hot pack may feel hot on the skin, but the heat penetration is merely 1 cm).

The utilized frequencies area high enough that muscles or nerves are warmed up but not stimulated.

It has two basic forms of application of SWD: Condenser field and Induction, both provide the same deep heat effect, but the implementation differs

  • Short Wave by condenser field: The area to be treated is placed between two electrodes or air spaced drums to close the circuit for the electromagnetic radiation to circulate. Modern equipment has an automatic tuning system that adapts to the fabrics to be treated taking into account the resistance they offer according to their aqueous content.
  • Short Wave by induction: This is the most common form of SWD, where the treated area is placed in a magnetic field – NOT part of a circuit.  The induction method utilizes a drum with a mono-head or with a triplet that allows better adaptation to areas such as the shoulder or knee.

what is diathermy photo


Diathermy treatments can be carried out with either thermal or athermal effect.

It is used in “continuous” mode for heat effect in depth, and the “pulsed” mode for molecular activation without thermal effect (e.g., in acute inflammatory cases)


What are the physiological effects of SWD?


The main effect of SWD is the increase in temperature of deep tissue such as blood vessels muscle tendons etc., increasing capillary pressure, oxygen perfusion and capillary filtration.

Adipose tissue is not a good conductor of electromagnetic radiation; therefore, temperature rising is minimal.

The amount of heat produced will be directly proportional to the size and force of the electromagnetic field (EMF) generated, the distance from the source and type of tissues to be treated.

The augmentation of temperature in the tissues will produce an active vasodilation, therefore, increasing the amount of blood flow to the amount of blood to area affected area

SWD generates heat in the interior of the organism, even in the deep tissues, but distributed homogeneously.

Once achieved, the heat propagates by conduction towards the colder zones via conduction, obtaining a thermal equilibrium.

As a consequence, the temperature of the tissues increases and therefore the vascularization increases, the metabolism, individual biochemical reactions trigger the therapeutic effects.

This warming must be kept within limits, because to an excessive degree it can cause irreversible injuries.

Physiological effects:

  • Skin: The sensation of heat on the skin is not very intense, due to a weak stimulation of the nerves, since its irradiation is homogeneous and it alters little the difference of the skin.
  • Effect on the bone, muscle, and joint tissue: it crosses these tissues as a displacement current and heats its interior as a driving current. The muscle tissue surrounding the bone is homogeneously heated. It increases extensibility of collagen fibers in tendons and joint capsules
  • Metabolism: from the heat it generates, acts as a catalyst for different chemical reactions, which stimulates metabolic activity. It produces stimulation of the synthesis of collagen; it increases oxygen consumption and increases the excretion of waste material. Reduces viscosity of fluid element within the tissues
  • Circulatory system: hyperemia on the skin is poorly manifested. It produces vasodilation on the vascular walls, which favors greater blood flow and supply of oxygen and nutrients, decreases the peripheral resistance by producing hypotension.
  • Nervous system: if the heat is not excessive, it decreases the excitability of the peripheral nerves and causes an increase in the pain threshold in them.
  • Anti-inflammatory effect: secondary to hyperemia, increased leukocytosis and phagocytosis, and the greater elimination of debris.

Specific Indications for Short Wave Diathermy

Most common indications for pulsatile short-wave therapy are:

  • Sprain
  • contusion,
  • rupture
  • muscle spasms
  • joint contractures or adhesions
  • hematoma, etc.
  • bursitis
  • tenosynovitis
  • pressure ulcers


Contraindications of Short Wave Diathermy

People with specific conditions may be at risk for injury or aggravation if they receive SWD.

These conditions include:

  • Fractures
  • Cardiac Pacemakers
  • Bone Graft
  • Epiphyseal plates in children
  • The abdomen with implanted IUD

It may not be appropriate if you present:

  • Hemorrhages: or tendency to them.
  • Acute vascular diseases
  • Pregnancy
  • Active tuberculosis
  • Anesthetized areas
  • Prosthesis, metal implants (however, there is still not a lot of evidence to prove that pulsed non-thermal diathermy is a harmful treatment with the presence of endoprostheses.)
  • Sensory loss
  • Malignant tumors: it may favor metastasis.
  • Genitalia
  • wound dressings
  • Eyes and face
  • Infection sites
  • severe heart, liver, or kidney conditions


Patients should not wear watches or any type of metallic objects even if they are at a distance from the area to be treated, attention to Cell phones and credit cards, they could be damaged.


How is the Application?

Depending on the type of SWD (Condenser field or induction) and the location of the area to be treated, you may lie on a table or sit in a chair during the application.

A towel or another interphase material may be placed over the area to avoid direct contact between the skin and the electrodes.




Also depending on whether thermal or non-thermal intensities are being administered, you may experience a warmth or tingling sensation, or you may feel nothing at all.


The typical treatment time is up to 20 minutes for Thermal applications and 30 minutes for non-thermal.

Dosage 1 or very weak, the intensity selected at non-thermal intensities and patient has no sensation of heat. (acute inflammatory processes, pressure wounds).

Dosage 2 or weak: the patient notices a slight sensation of heat (subacute processes and resolution of inflammatory processes).

Dosage 3 or medium: a moderate but pleasant sensation of heat (subacute processes and resolution of inflammatory processes).

Strong dose: vigorous heating but well tolerated by the patient (chronic processes).


What to Expect After SWD

After the SWD treatment, the compromises area will feel more relaxed and flexible, and most therapist will use before rehabilitation exercises. Pain may diminish or subside and normally the effects sustain for a long period of time.

SWD may be recommended until the condition heals.

thanks for taking the time to read “what is Diathermy focusing on Short Wave Diathermy” article. I hope you found it educational, if you have any comment or question, please ask in the comment section, thank you.

By |2018-10-26T03:05:12+00:00September 24th, 2017|Health Tips|0 Comments

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