ELECTRICITY & ELECTRONICS“For Anesthetist”

By

Prof. Gamal Elewa, MD

Faculty of Medicine, Ain Shams University

Anesthesia Department

©

Intended Learning OutcomesBy the end of this lecture , the post-graduate student will be able to:1. Know types of electricity and clinical applications2. Know General Electricity applications in

anesthesia3. Understand Equipment: Defibrillators, Cardiac

Pace Makers, Electro-cautery (surgical diathermy), Others: computer

4. Consider Electrical Safety and Avoid Electrocaution

General Electricity

• Definitions• Types of electricity: Static vs Dynamic. AC

vs DC. High vs low pressure lines• SI units: currenr (A), electr. Potential (V),

resist (Ω), ..• Classification of substances according to

their electrical conductivity: conductors, semi- conductors, insulators

©

Types of electricity

• Static vs Dynamic• Clinical importance of static electricity• Direct vs AC current

©

Direct & Alternating Current

• DC: Flows in one direction• AC: Periodically reverses its direction (sine

wave):

-Wavelength: distance between 2 waves

-Frequency: no. of waves/cycle

-Velocity: wave length X Frequency

©

ELECTRICAL SI UNITS

• Frequency: Hertz (Hz)= cycle/sec• Power: Watt (W)• Electrical current: Ampere (A)• Electrical Potential (EMF): Volt (V)=W/A• Electrical Charge: Coulomb (C)=As• Electrical Resistance (Impedance,

Reactance): Ohm (Ω)=V/A (Ohm’s Law)• Electrical Inductance: Farad (F)=As/V• Electrical Capacitance: Henry (H) =Vs/A

©

Electrical Conductivity

• Conductors: Metals, e.g. cupper, lead, platinum, gold, silver

• Insulators: glass, plastic, rubber, wood, mica, porcelin, ceramic

• Semiconductors: Silicon, germanium, selenium

- Used in: transistors, thermistors, diodes, some transducers

- Affected by temperature, e.g. thermistors

General Electricity

x

R2

R1R3

RxR2

y

• WHEAT STONE BRIDGE: R2/R1= R3/Rx

Medical Equipment

• Defibrillators• Cardiac Pace Makers• Electro-cautery (surgical diathermy)• Others: computer

Defibrillator

• Definition• Physical and Clinical Principles• Indications & uses: Cardioversion &

Defibrillation• How applied?• Precautions• Automated types

Pace Maker

• Definition• Principle• Uses (Indications)• Types• Terminology• Precautions

Pacemaker IdentificationMulti-site pacing (when 2 atria or ventricles are paced)

Programmable Response of generator to sensed P or R waves

Chamber sensed

Chamber paced

OAVD

O(fixed function)P(rate/output)M= multiprogramC=communicatinR=rate modulating

O(asynchronus)T=triggeredI=inhibitedD=dual=T+I

OVAD

OVAD

Electro-cautery (Diathermy)

• Def• Principle• Types: Unipolar vs Bipolar, coagulation vs

cutting• Precautions: general, with pacemaker

Electrocution

• Types: Macro-shock

Micro-shock• Why?• Prevention

©

Summary of important points

ElectricityDefinitionsTypes & ApplicationsEquipmentHazards & Their Prevention

©

Examples of questions to assess the ILOs

- Wheatstone bridge: principle and clinical applications- Electrical cautery: precautions with pacemaker- Physical principle of defibrillators & their types- Hazards of defibrillators- Difference(s) between: * Direct & alternating currents, * Monophasic & biphasic defibrillators, * Static & dynamic electricity

• THANK YOU