Diathermy

LOADING AWESOME

DIATHERMY

Dr. David Lyness

@Gas_Craic

propofology.com

MONOPOLAR & BIPOLAR

Surgical diathermy equipment uses the heating effects of high frequency (kHz–MHz) Electrical current coagulates and cut tissues.

There are two basic types – monopolar and bipolar

- Generates electrical energy at 200 kHz to 6 MHz.

- The energy is applied between two electrodes (neutral and active).

- The neutral electrode has a large conductive surface area producing a low current with no measurable heat effect.

- The active electrode has a very small contact area resulting in a very high current density.

- The heating effect beneath the active electrode is considerable producing deliberate tissue damage.

- Cutting diathermy employs a sine waveform whilst coagulation uses a modulated waveform.

- In basic terms, is usually a 'wand' with a patch/plate attached to the patient

- Not good with pacemakers! Can interfere.

- Underneath the patient plate should be checked after all procedures.

- There is an earth wire inside the diathermy machine

MONOPOLAR DIATHERMY

http://resources.ama.uk.com (diagrams)

http://ceaccp.oxfordjournals.org/content/3/1/10.full.pdf

- Bipolar diathermy operates with a much lower power output (15-20w for example)

- The output is applied between the points of a pair of forceps producing high local current density.

- No current passes throughout the rest of the body.

- NO PATIENT PLATE

- This is the only diathermy that should be used with pacemakers

BIPOLAR DIATHERMY

MONOPOLAR

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BIPOLAR

Modern ECG’s also contain floating or isolated circuits to avoid providing a route to earth for any stray currents.

- The patient plate is attached within the diathermy machine to an isolating capacitor.

- The diathermy current which is of high frequency flows easily across the capacitor

- Impedance decreases with increasing frequency of current

- The lower mains frequency is subject to a much higher impedance.

- The patient plate is prevented from becoming a route to earth via which currents from faulty equipment may be conducted.

ACCIDENTS

- Fires and explosions may be caused by sparks igniting flammable materials, e.g. skin cleaning solutions, bowel gas.

- Burns to the patient if the monopolar plate isn't connected properly and the patient comes in contact with a conductor

- Inadvertent firing is avoided by using a quiver for the diathermy device and avoiding hitting the pedals

David Lyness | March 08, 2020