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Technological Sciences for the Operating Room Electricity for the Surgical Technologist Introduction • W.T. Bovie developed first spark-gap tube generator • 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 medicine Surgical Applications of Electricity • 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 Electricity • X-ray Machine – Utilizes electromagnetic radiation – Uses of X-rays • View internal body structures • Determine presence of foreign bodies • Find retained sponges, sharps, or instruments • Verify presence of fluid or air • Assist in bone realignment Surgical Applications of Electricity • 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 control Surgical Applications of Electricity • 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 Electricity • Robotics – Extend and enhance human capabilities – Components • Robotic arm (manipulator), computers to operate the robotic arm and interpret commands, voicecard, video system and microphone – 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 electrons – Serves as basis for design of electrical equipment • Atoms, Electrons, Matter – Matter has mass and occupies space; consists of atoms Principles of Electricity • Atoms, Electrons, Matter – Atoms • Composed of protons, electrons, neutrons • Nucleus is center; contains positive charged protons and neutral charged neutrons • 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 electrons • 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 Magnetism • 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 magnetism Magnetism • 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 Magnetism • 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 Magnetism • Electromagnets con’t. – Example: Power plant • Water from dam heated forms steam turns turbines (generators) turbines spin magnets electricity is created for use Volts • 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 Current • Measured in amperes (amps) • Rate of flow of electrons • Current flow is the movement of free electrons • Free electrons attracted from point of excess electrons to a point with fewer electrons 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 Power • Rate at which work is completed – Rate of movement of electrons or current flow – Product of voltage & current is power –P=IxV • 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 Load • Device that uses electricity to perform a function • Can change amount of energy from power source • 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 Switch • 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 Wires – 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 Resistors • 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 needed – 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 down” – 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 waves – Radio transmitter delivers signal to antennae system – 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 circuit – 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 Electrosurgery • 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 Electrosurgery • 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 electrodes – 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 patient Electrosurgery • Shock and Burn – Patient • Burns usually deep; tissue necrosis; thrombosis • 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 Electrosurgery • 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 burn Electrosurgery • 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 SUMMARY • THE END