Chapter 9 Electrosurgical Unit

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Chapter 9Electrosurgical Unit
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History of ESU (Electrosurgical Unit)

• Thompson(1889) dArsonval(1891)
• ??? ??? ??? ???? ?? ? ???? ??? ??? ?? ??
• ?? ???? ??
• 1910
• fulguration(????) ?????? ?? ?? ??? ???? ????
  ??? ??
• desiccation(?????) ??? ??? ????(short
  spark)? ???? ? ???
• ?? ?????
  ???? ?? ??? ??
• 1928
• Cushing(neurosurgeon) Bovie(physicist)
  ???? ??
• ??
• Bloodless entry into the body for general
  surgery
• ??? ?????? ??? ??? ? (excise)
• ?? ??? ????? ??? ?
• ???? hair? ??
• ??? ??

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Therapeutic Effects of ESU

• Cutting
• Leading edge of an active electrode (?? ??
  ???)
• - electrode? tissue? ???? ?? ?? ?? ????? ???
  ??
• - electrode?? ???? tissue ?? ????? ??
• - electrode? tip? joule heating? ?? ?? ??
• - ???(cellular water)? ??? volatilized(??,
  ??)??? ??? ??
• Coagulation
• ?? ??? ?? ????? ?? ???? ???? ??
• (electrode ??? ??? ??? ???? drying ?? tissue
  destruction? ??)
• - Fulguration (????)
• ?? ??(??V)? electrode? tissue ???? spark
  ??
• Spark? ?? ??? ???? ?? ?? ???? ??? cutting
  ?? ??
• - Desiccation (?????)
• Electrode? tissue? ????? ? ??
• ??? ??? desiccation ??? ???? ??
• Volatilization? ???? ???? ??? ????, ?? ??
  ? ?? ? ??

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Essential Components of an ESU
300kHz 3MHz? ?? Electrode? 1,000-10,000V ??
active electrode
dispersive electrode - cutting electrode?? ??
??? - ????? ??? heating effect? ??
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Functional Circuits for Electrosurgery
Diterminal-unipolar
Diterminal-bipolar
Monoterminal
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Waveforms Generated from ESU
Sinusoidal Continuous wave (CW) 250KHz - 4MHz
Spark-gap waveform 500KHz
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Waveforms Generated from ESU
Continuous wave (cutting)
Spark-gap (coagulating)
modulated for (cutting coagulating)
Solid-state-generated blended (hemostatic)
Solid-state-generated (coagulating)
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Current Distribution between Electrodes and Tissue
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Types of Electrodes
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ESU Output Configuration
??? ?? ground
open ??? ??? ??
- passes all the RF current - blocks low
frequency current
- frequency dependent impedance ?? - ??? power
line frequency??? ??
ground type?? open circuit ??? ? ???? current
pathway??? ??
Isolation transformer
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ESU Equivalent Circuit
ESU internal resistance
Generated waveform
Active electrode skin resistance
Return electrode resistance
Body resistance
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Absorbed Power of an Active Electrode
Plot the power observed, , at the active
electrode as a function of , ranging from
to
Maximum power
? ? maximum power
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Return Electrode

• Electrosurgical current? ????? ???
• ???? ??
• - ?? ?? ???? ?? ? ???? ??
• - electrode? skin ??? resistance? ??
• (monitoring of the resistance)