Principles of radiofrequency and its ent applications

Dr. Juveria Majeed,MS ENT,

Govt.ENT Hospital/Osmania Medical College

• Within the surgeon’s armamentarium, electrosurgical devices stand out as some of the most useful and most used instruments.

• William T Bovie - father of elecrosurgical devices.

• The use of cautery dates back as far as prehistoric times, when heated stones were used to obtain hemostasis.

APPLICATIONS OF DIFFERENT CURRENT FREQUENCIES

• Electrosurgery: high-frequency electrical current passed through tissue to create a desired clinical effect. As the current is delivered, it passes through and heats the tissues.

• This differs from electrocautery, in which electrical current heats an instrument and a clinical effect is realized when the heated tool is applied to the tissues.

Principles of radiofrequency:

• Central to the understanding of electrosurgery is an understanding of electrical circuits and Ohm’s Law. Circuit is an uninterrupted pathway of flowing electrons and Ohm’s Law describes the actions of a given circuit:

• Voltage = Current*Resistance

• Current -flow of electrons during a given period of time.• Voltage -the force driving a current against the resistance of the

circuit.• In electrosurgery, voltage is provided by the generator, and current

is delivered to the tissues through the electrode tip of the instrument.

• Resistance to current is inherent within all human tissues.• The higher the inherent resistance, the greater the voltage needed

for the current to pass

• Electrosurgical generators were “ground referenced,” ie, the flow of energy was in relation to earth ground. In this situation, anytime the patient came in contact with a potential path to ground, the current would choose the path of least resistance. This potential hazard was eliminated with the introduction of generators that were isolated from ground, confining the current flow to the circuit between the electrode and the patient return electrode, which offers a low-resistance pathway for current to return to the generator from the patient.

• The transformation of electrical energy into heat occurs in accordance with Joules Law and can be expressed by the following formula:

• Energy= (current/cross-sectional area)2 *resistance*time.

• Heat produced is inversely proportional to the surface area of the electrode, ie, the smaller the surface area, the more localized heating energy is produced.

How does it work?• The rate at which tissues are heated plays a crucial role in

determining clinical effect. • When an oscillating current is applied to tissue, the rapid movement

of electrons through the cytoplasm of cells causes the intracellular temperature to rise.

• The amount of thermal energy delivered and the time rate of delivery will dictate the observed tissue effects.

• In general, below 45°C, thermal damage to tissue is reversible. • As tissue temperatures exceed 45°C (as in coblation and RF), the

proteins in the tissue become denatured, losing their structural integrity.

• Above 90°C, the liquid in the tissue evaporates, resulting in desiccation if the tissue is heated slowly or vaporization if the heat is delivered rapidly.

• Once the tissue temperatures reach 200°C( as in laser or cautery), the remaining solid components of the tissue are reduced to carbon. which can cause granulations, post op infections, morbidities like excessive scar tissue formation.

Types of electrosurgical instruments

• Electrosurgical technology offers essentially two types of devices for energy delivery:

monopolar and bipolar.• The monopolar instrument delivers current through an active

electrode which then travels through the patient and back to the generator through a conductive adhesive grounding pad applied to the patient before beginning the procedure.

• Bipolar instruments resemble surgical forceps, with both the active electrode and the return electrode functions being performed at the surgical site.

• The electrosurgical energy does not travel through the patient but is confined to the tissue between the forceps. Hence it clearly offers very little chance for unintended dispersal of current.

Types of RF Units

• Single Frequency A) low frequency- Machines operating at 1.0-2.9

MHz B) High frequency- Machined operating >3.0MHz

• Dual Frequency Machines operating at 1.7 & 4 MHz

• Coblator- Coblation is derived from the word ‘Controlled Ablation’

• It is actually cold ablation• It combines radiofrequency energy with a

natural saline solution.

What Is Coblation?• Bipolar configuration• RF current through conductive

solution– 100-300 V, 100-500 kHz

• Plasma field by RF current– In NaCl, orange glow

• Not heat-driven• Molecular dissociation• Minimal thermal penetration– Cell death (<125 mm)

Coblation• Low frequency

– Decreased tissue penetration – Minimal collateral tissue damage– Surface temperatures 40° to 70° C

• Shorter current path– Control of energy delivery

• Volumetric tissue removal

• Monopolar spark between electrode and tissue

• Localized tissue heating– 450° to 600° C

• Tissue desiccation and vaporization

Electrocautery

Waveforms OF RF

Fully filtered cut:• Microsmooth cutting• Negligble lateral heat• Minimal cellular

destruction• Ideal for skin incision

and biopsy• Best cosmetic results• Fastest heating

• Partially Rectified Coagulation:• Coagulation/shrinkage: Ideal for cutting with

hemostatic control.• Hemostasis with controlled penetration

• Fully Rectified Cut/ Coagulation:• Cutting with hemostasis• Ideal for subcutaneous tissue dissection and

planing especially useful in vascular areas while producing minimal amount of lateral heat and tissue damage.

• Fulgration:• Maximum penetration and

controlled hemostasis

• Bipolar:• Pinpoint microcoagulation• No tissue adherance to

forceps• No charring or tissue necrosis• Ideal for coagulation- in and

around critical anatomy

Mode Output waveform Output frequency Max. output power

1. Cut 90% cut10%coagulation

4.0 MHz 120W

2. Cut/Coagulation 50%cut50%coagulation

4.0MHz 90W

3.Hemo 10% cut90%coagulation

4.0MHz 60W

4. Fulgrate Spark- gap 4.0MHz 45W

5. Bipolar 10%cut 90%coagulation

1.7MHz 120w

• Physical Background: Injury to the tissue depands on the lateral heat generated by the probe of the instrument.

• Lateral heat formula• T*I*F*W*E• T- Time• I- Intensity of power• F- Frequency• W- Waveform• E- Electrode size

Comparision with other technologiesRadiofrequency Electrocautery

Simultaneous cut and coagulate Requires different mode for different application

Minimal surrounding tissue damage Tissue damage is more

Less lateral heat More lateral heat

Minimal scarring Gross scarring and fibrosis

Faster healing Slow healing

Less sloughMinimal infection

More slough formation causes infective nidus

Comparision with other technologies

Radiofrequency Laser

More precise cutting and coagulation Less precise

Self controlled of coagulation depth Less control

Less lateral heat damage More lateral heat damage

APPLICATIONS OF RF

Surgeries for snoring • Snoring is mostly caused

by the relaxed soft palate tissues.

• RF can be used to contract and stiffen the lax tissues thereby eliminating the main cause of habitual snoring

• RF used in a procedure where a part of tonsil tissue is precisely coagulated. This method leads to significant reduction in the tissue without compromising on lymphatic tissue.

Hypertrophy of tonsils

• Submucosal coagulation of hypertrophied turbinates all along the length of turbinated without damaging the epithelium and mucosa

Hypertrophy of turbinates

• A combination of variety of surgeries can be done to relieve obstruction:

• Nasal surgeries• Palatal surgeries• Tongue base reduction • Hypopharyngeal surgeries

OSA syndrome

• Choanal atresia repair• Nasopharyngeal obstruction:

RF suction adenoidectomy• Uvelectomy- elongated uvula

touching base of tongue, edematous uvula

• Somnoplasty: Palatal stiffening using RF can be performed along with uvelectomy, tonsillectomy, minimal palatoplasty.

Webbing and enlarged uvula

• UPPP- uvulopalatopharyngoplasty• Z palatoplasty• Expansion sphincter pharyngoplasty• (lateral pharyngeal wall collapse)• RF tongue base reduction• Partial glossectomy• Lingual tonsillectomy• Laryngomalacia- glossoepiglottopexy• supraglottoplasty• Laryngeal web excision• Glottic and supraglottic lesions- excision• b/l abd palsy- cordotomy• Polypectomy

ADVANTAGES OF RF

• 1) Low Temperature No risk of myoglobinuria as seen in laser surgery Scar tissue minimal Skin incision can also be given Painless Healing fast

2) Cosmetic results superior

3) Bleeding minimal- excellent hemostasis- clear surgical fields

• 4) Cost effective

• 5) Does not take up valuable OT space

• 6) No special protective gear

• 7)No interferance with histopathological reporting.

COMPLICATIONS

• Mainly occur due to improper technique• Intraop: Lacerations, Deep wound,

Hemorrhage( Duration and coagulation with ball electrodes helps in achieving hemostasis.)

• Mucosal ulcerations• Scarring ( can be avoided using appropriate

electrodes) proper power settings and most important by the technique of brief contact of the electrode with tissues.

• RF is contraindicated in pts with pacemakers( bcoz it interferes with signals).

• RF is undoubetedly most useful and most-often used tools at the surgeon’s disposal.

• But there are potential applications for which these electrosurgical instruments are not commonly used. For example, there is a pervasive dogma in surgery that skin is to be opened using the traditional scalpel, and deeper tissues may then be opened using the electrosurgical tool. The theory behind this proposition is that use of the Bovie causes worse cosmesis at closure and predisposes surgical wounds to postoperative infection. It is believed that electrosurgery devitalizes tissues at the wound edges, leading to approximation of dead tissue at closure.