Technological Sciences for the Operating Room Electricity for the

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Transcript Technological Sciences for the Operating Room Electricity for the

Technological Sciences for the
Operating Room
Electricity for the
Surgical Technologist
• W.T. Bovie developed first spark-gap tube
• Electrical burn is a serious risk to patients
• Patient Safety Depends on
– Knowing basic electrical terminology
– Principles of electricity
– Proper applications in O.R.
• Surgical technologists must learn theories
of electricity and usage for 21st century
Surgical Applications of
• Electrosurgical Unit (ESU)
– Generates current to cut tissue
– Direction of current flow:
• Generator → active electrode →
dispersive (inactive) electrode →
generator (Figure 6-6, Pg 115)
Surgical Applications of
• X-ray Machine
– Utilizes electromagnetic radiation
– Uses of X-rays
• View internal body structures
• Determine presence of foreign bodies
• Find retained sponges, sharps, or
• Verify presence of fluid or air
• Assist in bone realignment
Surgical Applications of
• Endoscopes
– Instrument inserted in patient through
abdomen, chest wall, or orifice
– Flexible or rigid
– Camera and light cord attached
– Used with ESU, laser or robotic arm
– Applications
• Diagnosis, obtain biopsy, repair,
retrieve foreign object, hemorrhage
Surgical Applications of
• Lasers
– Utilized in almost all surgical specialties
– Energy converted into light energy
– Laser light does not spread
– Choice of beam criteria
• Power, wavelength, color, duration of
exposure, type of tissue
– Laser classification
• Gas, solid, liquid, semiconductor crystals
Surgical Applications of
• Robotics
– Extend and enhance human capabilities
– Components
• Robotic arm (manipulator), computers to
operate the robotic arm and interpret
commands, voicecard, video system and
– Advantages
• Eliminates hand tremor (holding
endoscope); promotes faster recovery,
improves visualization of surgery site;
enable telesurgery; reduces costs.
Principles of Electricity
• Electron Theory
– All electronic effects caused by movement of
– Serves as basis for design of electrical
• Atoms, Electrons, Matter
– Matter has mass and occupies space;
consists of atoms
Principles of Electricity
• Atoms, Electrons, Matter
– Atoms
• Composed of protons, electrons,
• Nucleus is center; contains positive
charged protons and neutral charged
• Negative charged electrons travel in
orbits around nucleus
• Atoms held together by opposite
charges of protons and electrons
• Different elements have varying
numbers of protons and electrons
Principles of Electricity
• Atoms, Electrons, Matter
– Electrons
• Revolve in shells or orbits
• Close to nucleus – strong attraction; outer
orbits – less attracted
• Free electrons located in outer orbits;
movement creates electric current
• Electricity: term actually describes
movement of free electrons moving from
orbit of one atom to another (principle
based on Bohr’s Theory)
Principles of Electricity
• Atoms, Electrons, Matter
– Electrons con’t.
• A conductor is a material that allows flow of free
• The greater the number of electrons in a
substance, the better the conductor
• Copper is the most commonly used material for a
conductor. Silver, zinc and brass are also used.
• Devices in O.R. that use copper as a conductor:
surgical lamps, ESU, power drills
• Water is a conductor; humidity in O.R. should be
maintained at 50%-60%
Principles of Electricity
• Insulators
– Materials with small number of free electrons;
inhibit flow of electrons
– Basically poor conductors
– Used to wrap conductors to preserve current
and prevent leakage of electrons
– Types of insulators
• Rubber cord, plastic around ESU or
X-ray machine
Principles of Electricity
• Electrical Charge
– Can be either positive or negative
– Defined as too many or too few electrons
orbiting an atom
– Law of Electric Charge: like charges repel
each other; unlike charges attract each other;
opposites attract
Principles of Electricity
• Electrical Current
– Movement of electrical charge
– Current moves through conductors by
movement of free electrons migrating
from atom to atom inside conductor
• Magnetic Fields
– Electrons create a magnetic field or electric
charge while orbiting the nucleus
• In some materials electrons travel in
the same direction, combining
magnetic fields
• Natural magnetic substances include
iron, nickel, cobalt, even the earth
– Electrical generators depend on the
close relationship of electricity and
• Magnetic Fields con’t.
– Earth
• Two poles, north and south
• Magnetic field is lines of magnetic
force between poles
• Magnetic field causes metal objects to
be attracted to the magnet; needle in
a compass
• Electromagnets
– Metals that become magnetic when
encircled by a conductor
– Magnetic field created by current
traveling through conductor
– Magnetic field used to create electricity
• Electricity does not create power;
only means for transporting it
– Interaction between wires and magnets
produces power
• Electromagnets con’t.
– Example: Power plant
• Water from dam heated  forms
steam  turns turbines (generators)
 turbines spin magnets  electricity
is created for use
• Terminology
• Volt is electrical potential
– Voltage is potential energy of electrons
– Named after Alessandro Volta, a 17th
century scientist who invented the battery
• Electric system: battery creates voltage to
move electricity
• Circuit is the path electricity travels
• Measured in amperes (amps)
• Rate of flow of electrons
• Current flow is the movement of free
• Free electrons attracted from point of
excess electrons to a point with fewer
Ohm’s Law
• Scientific law of electricity
– Mathematical equation showing how voltage,
current, and resistance interrelate
– Ohm’s Law: V = I x R
• Resistance
– Restricting flow of current; measured in ohms
• Ohm’s Law
– More voltage will increase current if resistance
is constant; higher resistance causes
decreased current if voltage is constant
• Rate at which work is completed
– Rate of movement of electrons or current flow
– Product of voltage & current is power
• Measured in watts (W)
– Converted to kilowatts (KW): 1 KW = 1,000 W
– Example: DC Circuit is 12V & 20A, Power is
P = 20 x 12 = 240W or 0.24KW
• Device that uses electricity to perform a function
• Can change amount of energy from power
• Examples: surgical lamps, ESU, power drills,
video monitors
• Resistive energy loads: conductor has high
resistance to flow of electricity
– Example: filament (conductor) in light
bulb; electricity has to force way thru
resistance to cause filament to glow
• Device used to open or close circuit
– Controls flow of electricity
• Example: Flashlight
– Batteries (power)
– Wires (conductors) connected to battery that
is connected to switch activated by user
– Bulb (load) must have voltage
– Voltage carried by conductors and switch
controls flow of current to load; open switch –
no flow, closed switch bulb lights up
• Hot Wire
– Wire that connects to switch; colored red
• Neutral Wire
– Pathway for electrons to return to energy
source; complete the circuit; colored green
• Ground Wire
– Sends leaking electrons to ground to prevent
shock; colored black
• Devices made of materials that are
purposely resistive
• Designated with letter R
Direct Current (DC)
• Electrical current flows in one direction –
negative to positive pole
• Example: Batteries
– Serve as storage device; keep electricity until
– Negative (-) and positive (+) terminals
– When switch is closed, current flows from one
terminal to the other
Direct Current (DC)
• Batteries con’t.
– Four components of DC circuit
• Battery: source of electricity
• Wire (battery to load): conductor
• Switch: control device
• Load: bulb
Alternating Current
• Current that periodically reverses direction
• Complete cycle is current that moves in
one direction, then reverses direction
• Hertz (Hz): one AC cycle
• Frequency: number of AC cycles in a
second; symbol ƒ
• Most common AC in U.S. is 60 cycle AC
• Typical voltage is 110V or 120V
Alternating Current
• AC Can Change Voltage
– AC delivered as high voltage, then “stepped
– Example:
• Transformers “step up” exiting voltage
• Power lines (transformer) deliver electricity
at high voltage
• Voltage is stepped down before use
Radio Frequency (RF)
• Frequency is number of wave cycles (one
cycle is a hertz) per second
• Radio and TV signals are electromagnetic
– Radio transmitter delivers signal to antennae
– Electromagnetic signals travel through cable,
air or optical fiber to receiving antennae
– RF spectrum begins at 9 kHz (or less) to over
3 GHz
Isolated Circuit
• Cause of electrical shock
• Secondary circuit contains hazardous
current due to isolated circuit
– Transformer insulation isolates secondary
– Person touches both poles of non-insulated
isolated circuit and experiences an electrical
shock and/or burn
Isolated Circuit
• Secondary Circuit con’t.
– Two methods of prevention:
• Solid insulation placed as total barrier
to prevent complete access to circuit
• Conductive barrier of insulation
between isolated circuit and
conductive barrier
• Application of electrical current through
tissue to coagulate bleeding or cut tissue
• Electrosurgical Unit (ESU): Device that
provides power for electric current
• Electrosurgery: Electrical currents applied
directly to tissue; utilizes AC current
• Electrocautery: Uses heated wire to burn
tissue; no electricity enters body; utilizes
DC current
• ESU Circuit: Current Flow
– Generator  thru conductor cord 
active electrode (Bovie tip)  surgical
site (energy converted to thermal energy
to cut or coagulate)  thru patient 
dispersive electrode (grounding pad) 
conductor cord  generator
Bipolar Electrosurgery
• Used for delicate procedures, presence of
moisture, prevent nerve damage
• Two prongs of forceps: active and inactive
– Current travels through one tip, passes thru
tissue, disperses to other tip
• No dispersive electrode required
Monopolar Electrosurgery
• Flow of current is as described.
• Dispersive Electrode (grounding pad)
– Placement is critical to avoid electrical burns
to patient
– Pad must be in complete contact with
patient’s skin
– Pad pulled up or portion not in contact, may
result in second or third degree burns to
• Shock and Burn
– Patient
• Burns usually deep; tissue necrosis;
• Debridement
– Sterile Surgery Team Members
• RF Capacitive Coupling: AC travels
from active electrode, through intact
insulation, burns skin; apply active
electrode beneath Crile held by
surgeon to prevent burns
• Shock & Burn con’t.
– Sterile Surgery Team Members
»Dielectric Breakdown: High
voltage breaks down insulating
material, such as sterile glove;
produces hole in glove – surgical
team member sustains small
• Vaporized Tissue Plume
– Occurs during procedures involving
electrosurgery, lasers, power drills
– Plume is vaporized tissue
– Contains hazardous bioparticles that are
carcinogenic, mutagenic, and they may carry
bloodborne pathogens
– Surgical technologists utilize suction to “suck
smoke” from wound when using
electrosurgery or smoke evacuators for lasers