Electrosurgical units are classified into conventional high-frequency electrosurgical units and radiofrequency electrosurgical units based on their operating frequencies and waveforms. The two types differ mainly in working principles and practical performance. To begin with, radiofrequency electrosurgical units operate at higher frequencies ranging from 1.71 MHz to 4.0 MHz, while conventional high-frequency electrosurgical units work within the frequency band of 450 kHz to 650 kHz.

For conventional high-frequency electrosurgical units, electric current travels through the electrode. The smaller the contact area between the electrode and human body, the greater the impedance, which in turn causes a sharp surge in heat at the contact site. This intense high heat ruptures heated cells and induces rapid coagulation (analogous to a balloon scorched and burst by extreme heat), achieving cutting or hemostasis effects.

The working principle of radiofrequency electrosurgical units is completely different from that of conventional high-frequency electrosurgical units. Instead of electric current, the working tip of its electrode outputs radiofrequency electromagnetic waves ranging from 1.71 MHz to 4.0 MHz. Under the action of this localized high-frequency electromagnetic field, abundant polar water molecules inside cells oscillate rapidly and collide with one another, rupturing cell walls to achieve cutting effects.

Meanwhile, these water molecules generate heat through friction during high-speed movement, efficiently converting electric energy into thermal energy. As blood temperature rises, soluble fibrinogen in plasma transforms into insoluble protein monomers. Subsequently, under the effect of thrombin, these protein monomers further polymerize into protein multimers. The multimers interweave to form a mesh that traps blood cells, creating blood clots and completing the coagulation process efficiently.

Radiofrequency electrosurgical units adopt a higher frequency band of 1.71 MHz to 4.0 MHz, while conventional high-frequency electrosurgical units operate at a lower frequency range of 450 kHz to 650 kHz. Differences in frequency and waveform lead to distinct working principles and clinical performance. Furthermore, varying frequencies alter the propagation path of electric current, which affects tissue impedance and heat generation in human tissues, and ultimately determines the cutting and hemostatic outcomes.

Conventional high-frequency electrosurgical units generate heat by passing electric current through electrodes, whereas radiofrequency electrosurgical units produce heat via the oscillation of intracellular water molecules induced by radiofrequency electromagnetic waves, resulting in different performance characteristics.

Due to different working principles, conventional high-frequency electrosurgical units require a neutral electrode plate to form a current loop. The neutral electrode plate must have a sufficiently large area and maintain good contact with the patient’s body, so as to prevent excessive temperature from causing tissue carbonization or protein denaturation and subsequent burns. In addition, a certain amount of mechanical force needs to be applied during cutting with conventional high-frequency electrosurgical units, which often results in larger wounds and prolonged healing time. Therefore, such devices are mainly used in major surgeries.

Radiofrequency electrosurgical units require no neutral electrode pad, offering flexible operation and low-temperature cutting. They can be placed over surgical drapes or clothing, even far away from the operative field, which minimizes thermal damage to human tissues. Its low-temperature cutting range of 40℃ to 70℃ greatly reduces lateral thermal injury to tissues, resulting in tiny wounds and rapid healing. For this reason, radiofrequency electrosurgical units are widely adopted in minimally invasive and delicate surgeries.