Mon22November0200PM 7

Which of the following is more specific to bipolar compared with unipolar diathermy?

(Please select 1 option)

Uses high current density to coagulate and cut

May interfere with pacemaker function Incorrect answer selected

Has a power output of up to 140 joules per second This is the correct answer

Requires an isolating capacitor

Has a frequency of 500 KHz - 1 MHz

Explanation

Electrocautery or diathermy uses high frequency current to generate heat to enable coagulation, cutting of tissue or fulguration (cell destruction from dehydration).

With bipolar diathermy the two electrodes are the tips of forceps and current passes between the tips and not through the patient. The power output of bipolar diathermy (40-140 W) is less than the typical output of unipolar diathermy (400 W). The bipolar circuit is not earthed.

Unipolar diathermy has a cutting electrode and an "indifferent" electrode in the form of a metal plate. The high frequency current passes through the patient from the active electrode to the metal plate to complete a circuit. The current density at the indifferent electrode is low when correctly applied and unlikely to burn the patient. An isolating capacitor is placed between the patient plate and the earth. This is incorporated into modern diathermy machines and has a low impedance to a high frequency current, that is, diathermy current. The capacitor has high impedance to 50 Hz current, protecting the patient against electrical shock.

Both unipolar and bipolar diathermy use high frequency currents (500 KHz - 1 MHz) sufficient to cause tissue damage and have the potential to interfere with pacemaker function (less so with bipolar diathermy).

The effect of diathermy depends upon current density and the waveform used. In coagulation mode the current is a pulsed square wave and in cutting mode the current is a continuous square wave pattern.

Answer Statistics

1

31%

2

14%

3

14%

4

22%

5

21%

Times answered: 261