Diathermy is electrically induced heat or the use of high-frequency electromagnetic currents as a form of physical therapy and in surgical procedures. The earliest observations on the reactions of the human organism to high-frequency electromagnetic currents were made by Jacques Arsene d'Arsonval. It exerts physical effects and elicits a spectrum of physiological responses.

The same techniques are also used to create higher tissue temperatures to destroy neoplasms, warts, and infected tissues; this is called hyperthermia treatment. In surgery, diathermy is used to cauterize blood vessels to prevent excessive bleeding. The technique is particularly valuable in neurosurgery and in eye surgery.

History

thumb|right|Diathermy treatment in London, 1918

The idea that high-frequency electromagnetic currents could have therapeutic effects was explored independently around the same time (1890–1891) by French physician and biophysicist Jacques Arsene d'Arsonval and Serbian American engineer Nikola Tesla. d'Arsonval had been studying medical applications for electricity in the 1880s and performed the first systematic studies in 1890 of the effect of alternating current on the body, and discovered that frequencies above 10 kHz did not cause the physiological reaction of electric shock, but warming. He also developed the three methods that have been used to apply high-frequency current to the body: contact electrodes, capacitive plates, and inductive coils. insist that electrosurgery be applied to surgery accomplished by high-frequency alternating current (AC) cutting, and that "electrocautery" be used only for the practice of cauterization with heated nichrome wires powered by direct current (DC), as in the handheld battery-operated portable cautery tools.

Types

Diathermy used in surgery is of typically two types.

  • Monopolar, where electric current passes from one electrode near the tissue to be treated to other fixed electrode (indifferent electrode) elsewhere in the body. Usually this type of electrode is placed in contact with buttocks or around the leg.
  • Bipolar, where both electrodes are mounted on same pen-like device and electric current passes only through the tissue being treated. Advantage of bipolar electrosurgery is that it prevents the flow of current through other tissues of the body and focuses only on the tissue in contact. This is useful in microsurgery and in patients with a cardiac pacemaker.

Risks

Burns from electrocautery generally arise from a faulty grounding pad or from an outbreak of a fire. Monopolar electrocautery works because radio frequency energy is concentrated by the surgical instrument's small surface area. The electrical circuit is completed by passing current through the patient's body to a conductive pad that is connected to the radio frequency generator. Because the pad's surface area is large relative to the instrument's tip, energy density across the pad is reliably low enough that no tissue injury occurs at the pad site. Electrical shocks and burns are possible, however, if the circuit is interrupted or energy is concentrated in some way. This can happen if the pad surface in contact is small, e.g. if the pad's electrolytic gel is dry, if the pad becomes disconnected from the radio frequency generator, or via a metal implant. Modern electrocautery systems are equipped with sensors to detect high resistance in the circuit that can prevent some injuries.

As with all forms of heat applications, care must be taken to avoid burns during diathermy treatments, especially in patients with decreased sensitivity to heat and cold. With electrocautery there have been reported cases of flash fires in the operating theatre related to heat generation meeting chemical flash points, especially in the presence of increased oxygen concentrations associated with anaesthetic.

Concerns have also been raised regarding the toxicity of surgical smoke produced by electrocautery. This has been shown to contain chemicals which may cause harm to patients, surgeons and operating theatre staff.

For patients that have a surgically implanted spinal cord stimulator (SCS) system, diathermy can cause tissue damage through energy that is transferred into the implanted SCS components resulting in severe injury or death.

Military

Medical diathermy devices were used to cause interference to German radio beams used for targeting nighttime bombing raids in World War II during the Battle of the Beams.

See also

  • Dielectric heating
  • Heat therapy
  • Pulsed electromagnetic field therapy

References