5 electrosurgery medical equipment

1. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Lecture-5: Electrosurgery
Sherif H. El-Gohary , Phd
Assistant Professor, Biomedical Engineering
Sh.ElGohary@eng1.cu.edu.eg
Medical
Instrumentation
SBE 310

2. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Learning objectives
 Introduce Diathermy
 Electrosurgical Unit
 Working Principle and Block Diagram
 Monopolar and Bipolar
 Safety considerations
 Diathermy Types

3. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
INTRODUCTION
Diathermy is a therapeutic treatment commonly prescribed for
muscular and joint associated pains.
The term ‘diathermy’ means ‘through heating’ or producing
deep heating directly in the tissues of the body.
‘ Dia’ through (also means two)
‘thermy’ heat or temperature
 It simulates the circulation, relieve pain, enhances rate of
recovery of healing the tissue.

4. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Definition
• Devices intended for surgical cutting and for
controlling bleeding by causing coagulation at the
surgical site.
• Electrosurgery is commonly used in dermatological,
gynecological, cardiac, ocular, spine, maxillofacial,
orthopedic, urological, neuro- and general surgical
procedures as well as certain dental procedures.

5. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
PRINCIPLE OF DIATHERMY
1. Before injury, the dipole molecules of the
body tissue are arranged on the basis of
polarity .
2. When the tissue is damaged the dipoles
distribution become irregular and deviates
from polarity based arrangement .
3. Under the influence of an electric field , they
rotate according to the polarity of their
charge in the direction of the field lines and
get rearranged and tends to acquire its
previous stage of polarity.

6. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Source : Fundamentals of Electrosurgery
by Malcolm G. Munro William T. Bovie

7. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Electrocautery is NOT Electrosurgery
The terms electrocautery and electrosurgery are
frequently used interchangeably; however, these
terms define two distinctly different modalities.
• Electrocautery: use of electricity to heat an
object that is then used to burn a specific site e.g.
a hot wire
• Electrosurgery: the electrical current heats
the tissue. The current must pass through the
tissue to produce the desired effect..

8. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Electrosurgery vs. Electrocautery
• Passing electrical current
through tissue
Electrosurgery
• Current is used to heat a
handheld element, which
is then applied to the
tissue
Electrocautery

9. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Temperature vs.
tissue effects
45 degree C: collagen uncoils & may
reanneal
60 degree C: irreversible protein denaturation,
coagulation necrosis begins; blanching
80 degree C: carbonization begins; drying and shrinkage
of tissues
90-100 degree C: complete cellular destruction by
vaporization; plume of gas and smoke
125degree C: complete oxidation of protein & lipids;
carbon residue & eschar formation

10. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|

11. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Working Principle of Electrosurgery
• Radiofrequency starts at about 3 KHz and extends through about 300 GHz
In this frequency neither muscular nor neural cells depolarize.
• The ESU converts electrical energy drawn from the mains supply to a high
frequency current.
• This high frequency current is passed through a supply cable and a handle
to an active spot electrode.
• At the point of application, this electrode builds up a highly concentrated
field in the tissue surrounding the contact point.
• The concentration of energy within a small area produces the desired
electrosurgical effect in the region around the active electrode.
• As the energy is conducted through the patient to a neutral electrode, in
contact with a large surface. (Therefore in the vicinity of the neutral
electrode, there is, as is intended, no thermal effect.)

12. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
High current density at the narrowing of
an electrical conductor creates heat
220 Volt
50 -60 Hz

13. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
DC Vs. AC

14. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|

15. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Why not 50 Hertz!!!
• Alternating current at frequencies from
1 to 100,000 Hertz will interfere with the neuro-
muscular system.
• Above 100,000 Hertz these stimuli occur too
quickly to affect the neuro-muscular system.

16. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Electrosurgery works by cutting, fulguration or
desiccation.
60 Hz 100 kHz 550-1550 kHz 54-880 MHz
Household
appliances
AM radio
TV
500 kHz-33 MHz
Electrosurgery
Frequency (Hz)
Cutting Desiccation
Nerve and muscle
stimulation
Fulguration / spray
coagulation

17. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Joules 5th Law
 Electrosurgical instruments are based on the principle of converting
electrical energy into heat
 The relationship of the amount of heat to the electric current (I), the
ohmic resistance (R) and the duration (t) is expressed:
𝑯 = 𝑰 𝟐 𝑹𝑻
– Burn
𝐵𝑢𝑟𝑛 =
𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑥 𝑇𝑖𝑚𝑒
𝐴𝑟𝑒𝑎

18. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Block diagram of a typical
electrosurgical unit

19. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Power control Power supply Oscillator Modulator
Power
amplifier
Plate
monitor
Actual current pathway
Alternative current
pathway
PatientPower output
stage
Cut/ coag
controls
Cut
Coagulate
Signal
generating
stage
MOSFET
Waveform
selection
Active electrode
Return
electrode
Alternative
current
pathways(ECG
electrode, etc)
Components of a modern electrosurgical system

20. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Components of a modern electrosurgical system
 The waveform selection and signal generating stage provide the
desired waveforms for cutting or coagulation.
 The power output stage employs power transistors such as
MOSFETs to amplify the waveforms and output them through an
output isolation transformer.
 This is then applied through a system of electrodes where the
current usually takes the path from the active electrode and back
through the return electrode, or alternatively flows through other
undesired low impedance pathways such as lead wires attached to
ECG electrodes.

21. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Electrosurgery Generator (ESU)
Active Electrode
Bipolar Forceps
Components of a modern
Electrosurgery Device

22. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Patient Return Electrode
Footswitch

23. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Types of ESU
Monopolar
Bipolar

24. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
1. Monopolarelectrosurgery
• Most commonly used electrosurgical modality.
• The active electrode is in the wound.
• Patient return electrode is attached somewhere
else on the patient.
• The narrow active electrode concentrates the
current (and therefore the power), at the
designated site.

25. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
1. Monopolar
3 basic components:
1. Generator,
2. Active electrode,
3. Patient return electrode
Produce variety of tissue effects depending on
waveform
Modes: Cutting and Coagulation
High power output, peak voltages and rated load
than bipolar type.

26. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Monopolar electrosurgery

27. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Basic electro-surgical circuit – (Monopolar)
Surgeon
Source - Gen
Patient
Return cable/path
Active cable/Path
Power supply
Patient Return
Electrode

28. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|

29. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Monopolar Electrosurgery
Cut
Pure Blend
Coagulation
Fulguration Dessication

30. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
• Cutting: divide tissue with electric sparks that
focus intense heat at surgical site
-By sparking we achieve maximum current
concentration
• Fulguration: sparking with coagulation
waveform
-coagulates and chars the tissue over a wide area,
result in coagulum
-high voltage coag current is used(duty cycle 6%)
Electrosurgical tissue effects

31. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Electrosurgical tissue effects
• Desiccation: occurs when electrode is
in direct contact with the tissue
- -Achieved most efficiently with cutting
current
- -by touching electrode to the tissue, current
concentration reduced, result in less heat and
no cutting action
- -cells dry out and form a coagulum

32. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Wave forms
pure cut blend cut desiccation fulguration
Pure cut uses the lowest level of voltage

33. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Tissue effects with waveform modification
• Cut waveform: Duty cycle(“on” time) is high,
continuous waveform
• vaporize or cut tissue,
• Produce heat very rapidly
• Coagulation waveform: intermittent
waveform
• Duty cycle (“on” time) reduced,
• Produce less heat so coagulum is formed
• Blended current : not a mixture of cutting
and coagulation, but a modification of duty
cycle
Only variable that determine vaporization or coagulation is rate of heat
High heat, more rapidly : vaporization
Low heat, more slowly : coagulum

34. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Spray coagulation
or fulguration Blade electrode
Bleeding vesselPrinciple:
Current follows
Path of least
resistance

35. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Pure cut Blend Fulguration/non contact coag

36. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Desiccation 1

37. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Desiccation 2

38. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Desiccation 3

39. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Patient Return Electrode
• Designed with an adhesive to facilitate continuing contact with
the patient and prevention of a clinically significant local
thermal effect.
• If there is partial detachment, the current (or power density)
will increase, and the dispersive electrode can become “active”
and capable of creating thermal injury, often called a burn.

40. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
• To avoid this they are designed in the form of a “split pad”
(which effectively is two dispersive electrodes in one) to measure
the impedance at the level of the electrode.
• A difference in the measured impedance in the two dispersive
electrodes will generally reflect partial attachment (or
detachment) and the machine will not start.
• Surface area impedance can be compromised by: excessive hair,
adipose tissue, bony prominences, fluid invasion, adhesive
failure, scar tissue, and many other variables.

41. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
2. Bipolar
• Both electrodes mounted on the device
• Usually located on or near to the distal end so that
only the tissue located between the two electrodes is
included in the circuit.
• Patient Return Electrode is absent.
• Three types of operations
– Precise
– Standard
– Macro

42. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Bipolar Electrosurgery

43. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|

44. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Limiting power settings by limiting contact
Blade electrode Micro Needle electrode
Choice of electrode & technique determines tissue effect
Forceps - tips

45. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
The electrosurgical effect is influenced by:
1. Contact Time
2. Power Settings of Generator
3. Type of electrode used (Current Density)
4. Whether Cut or Coag activated
5. Tissue Impedance
6. Distance from Active to Return

46. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Output Characteristics at Different modes

47. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Calculate tissue temperature using the bioheat equation
Where
T = final temperature (K)
 = electrical conductivity (S/m)
 = tissue density (kg/m3)
c = tissue specific heat(J/kgK)
J = magnitude of current density (A/m2)
t = duration of activation (s)
T0 = initial temperature (K)
also,
J = E,
Where E = electric field vector (V/m)
0
21
TtJ
c
T 

Governing Equation

48. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Example Assume that a uniform tissue has an electrical conductivity of
0.25 S/m, a density of 1000 kg/m3 and specific heat of 4186 J/kgK. If the
electric field applied is of the order of 8000 V/m, estimate the time of
activation required to reach a tissue temperature of 55 C assuming the initial
temperature to be the body temperature (37 C).
Given  = 0.25 S/m;  = 1000 kg/m3; c = 4186 J/kgK; E = 8000 V/m;
T0 = 310 K; T = 328 K;
Solution:
Using the bioheat equation and substituting the given values yields
J = 2000 A/m2
Substituting the calculated value of J yields,
which gives the value of t = 4.7 s
K310)A/m2000(
KJ/kg4186m/kg1000S/m25.0
1
K328 22
03


 t

49. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Safety considerations
Direct Coupling
• occurs when the active electrode touches another
metal instrument.
• The electrical current flows from one to the other
and then proceeds to tissue resulting in unintended
burn.
• This can also occur if an active electrode is
activated while in contact with a metal clip.
• So, do not activate the generator while the active
electrode is touching a metal object.

50. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|

51. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Insulation Failure
• Insulation failure can occur when the insulation covering
of an endoscopic instrument has been damaged
• Cracks or breaks in the shaft’s insulation allow the
electrical energy to escape and burn unintended tissue.
• Most damage to insulation occurs during instrument
processing, specifically during sterilization. Heat with
subsequent cooling causes insulation to shrink and then
expand. During this process cracks and breaks can occur.

52. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Insulation failure
• Coagulation waveform is high
in voltage, which can spark
through compromised
insulation. Also high voltage
can blow holes in weak
insulation.
• We can get the desired
coagulation effect without high
voltage , simply by using the
‘cutting’ current by holding
the electrode in direct contact
with tissue

53. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Insulation Failure

54. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Thermal injury caused by Insulation Failure of electro-surgical instrument
during Laparoscopic Cholecystectomy

55. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
TYPES OF DIATHERMY
1. SHORT WAVE DIATHERMY
2. LONGWAVE DIATHERMY
3. MICROWAVE DIATHERMY
4. ULTRASOUND DIATHERMY
5. LASER DIATHERMY

56. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
SHORTWAVE DIATHERMY
 Shortwave diathermy uses high-frequency
electromagnetic energy to generate heat.
 It may be applied in pulsed or continuous energy
waves.
 It is used to treat pain from sinusitis, kidney
stones, and pelvic infections.

57. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Shortwave has three main frequencies
:
 27.12 MHz(most common used one).
 13.56 MHz.
 40.68 MHz.

58. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
LONGWAVE DIATHERMY
 Long wave diathermy is based on capacitor field method.
It can work in heavy voltage fluctuation
Long wave can be used as an alternative for shortwave
diathermy applications.
 it is portable and light weight .

59. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
MICROWAVE DIATHERMY
 Microwave diathermy uses microwaves to generate heat
in the body.
 It can be used to evenly warm deep tissues without
heating the skin.
 Since it can’t penetrate deep muscles, it is best suited
for areas that are closer to the skin, such as shoulders.

60. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
ULTRASOUND DIATHERMY
 Ultrasound diathermy uses sound waves to treat deep
tissues.
 Heat is generated by the vibration of the tissue.
 This promotes blood flow into the area.
 It is used for many types of musculoskeletal sprains,
strains, and fractures.

61. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|
Examples of ablation procedures that are currently performed in clinics.
C = cryoablation, US = ultrasound ablation, RF = radio-frequency, MW
= microwave.
Application Technique
Cardiology (cardiac arrhythmias) RF
Urology (benign prostatic hyperplasia,
gallbladder)
C, US, laser, RF
Neurology (brain cancer) US, RF
Oncology (tumors) MW, RF, C, laser
Dentistry Laser, chemical
Ophthalmology (cataracted lens,
corneal sculpting, astigmatism)
Laser, US

62. P: 555.123.4568 F: 555.123.4567
123 West Main Street, New York,
NY 10001
www.rightcare.com|