Understanding Electricity and Coulomb's Law

• Electricity involves the shift in potential energy, facilitated by the movement of electrons from an area of high concentration to an area where concentration is low.
• Mobile charges are responsible for electrical phenomena.
• Charges come in quantized or discrete units
• There are two types of charge: positive and negative.
• Like charges repel each other while unlike charges attract.

Law of Conservation of Electric Charge

• The total amount of electric charge in the universe remains constant.
• Charges are mobile, and electrons, which are negatively charged, are the particles that move.
• The fundamental unit of charge is 'e', representing a single electron's energy, which is minute.
• A coulomb [koo lom] measures quantized energy

Coulomb

• The coulomb (C) stands as the SI unit of electrical charge.
• A single electron carries a charge of around 1.602 × 10-19 C.

Coulomb's Law

• Like charges repel, while opposite charges attract, and this force acts inversely to the square of the distance between them.
• Opposite charges positioned closely exhibit greater attraction, and like charges repel more intensely when near each other.
• The electrostatic, also known as coulombic, force is the attraction between two charges.
• The magnitude of electrostatic force between two fixed point charges is given by Coulomb's law.
• Coulomb's law indicates the magnitude, not the direction, of the electrostatic force between charges
• The force's directionality depends on the signs (+/-) of the charges involved.
• The force between them is very large.

Electric Field

• Every charge has a force field that applies electric force on a test charge surrounding a central charge
• Electric field uses newtons per coulomb (N/C) as its SI units.

Electric Potential Energy

• Potential energy occurs when a charge at rest is put in place, acquiring kinetic energy but not moving.
• Electric force is the force field that surrounds every charge, and this force applies its effects on any test charge positioned around a central charge.
• Electric potential energy is the name for this.
• Joule represents the SI unit for electric potential energy.

Electric Potential

• Electric potential measures energy per charge unit, quantified as a volt (V) or E.
• The SI unit for potential difference is the Volt, with 1 J/C (Think Force).

Electric Current

• Electric current, symbolized as I, measures the amount of charge flowing per unit time within a conductor.
• Electric current is the flow through a conductor, like copper wire
• The SI unit, ampere (A), is the unit of measurement for current: 1 A = 1 C/sec.
• The symbol for amp is I.

Electrical Conductor

• Electrical conductors are materials that permit easy charge movement.
• Metals are good electrical conductors.
• Atoms that lack tightly held electrons form good electrical conductors.
• Metals make good conductors, as they have outer electron shells with few electrons.

Electrical Insulators

• . Electrical insulators are materials that restrict charge movement.
• Electrical insulators are also known as dielectrics – insulator mediums
• Most insulators are nonmetallic.
• Good insulators can maintain a significant static charge.

Semiconductors

• Display electrical conductivity properties of both electrical conductors and insulators
• Made of semimetals like silicon
• Used in electronic devices like computers
• Minute impurities known as doping agents can control the conductivity
• Transistors are useful amplifying or switching circuits

Resistance

• All materials impede the flow of electrons under ordinary conditions.
• The measure of a material's resistance is the energy required to move electrons through it.
• For a material with constant resistance R, the relationship between potential difference V (voltage) and current I is: V = IR or R = V/I (or R = V/A)
• Ohm’s Law: V = IR

Conductance

• Voltage (electromotive force or driving pressure) = current x impedance
• Focusing on the SI units, R = V/A
• A volt divided by an ampere equals an ohm (Ω), which is the SI unit of resistance.
• The conductance G is the reciprocal of resistance
• Conductance is measured in siemens (S) or mho, equivalent to 1/Ω.
• G = 1 / R

Electrical Power

• A change in electric potential energy arises from a charge moving across a potential difference, represented by V.
• Power (P) consumed or dissipated by an electrical circuit is calculated: P = IV (or AV). Watts | Amps Volts amps = watts / volts
• The SI unit of power is the watt, calculatable as 1 watt = 1 W = 1 AV.

Electrical Energy

• Multiplying power by time gives energy: energy = power × time (work).
• Electrical companies use kilowatt-hour (kWh) as the standard energy unit.
• Thinking of electricity as water flowing through a pipe can help us understand amps, volts and watts
• If water is used as an analogy of electricity:
  • The water pressure (on or off) would be the voltage (force).
  • Amps would be the volume of water flowing through the pipe (0 or on).
  • Watts would be the power (volts x amps) the water could provide (filling up slow or fast?).

Electrical Diagrams

• Diagrams help represent electric circuits schematically.
• A circuit is required for charge flow.
• Symbols in electrical diagrams identify circuit elements like batteries, switches, and resistors.
• Direct current (DC) circuits feature current flowing in one direction
  • Direct current circuits typically use batteries
• Periodically changing direction at 60 Hz defines alternating current (AC) circuits
  • Alternating current circuits generally use wall outlets or AC generators (power companies) – oscillates between + and – voltage.
• Impedance in AC refers to resistance, characterized by capacitance and inductance.
• Capacitance refers to the capacity to store positive and negative charges.
• Wireless power transfer uses induced magnetic waves to transfer current without contact.

Series Circuits

• Series circuits posses only one path for current such as in flashlights
• In series circuits, battery voltages add, and resistors behave like batteries.

Parallel Circuits

• Parallel circuits provide multiple paths for current with junctions and wire intersections.
• Household circuits are parallel, ensuring electricity can flow through individual appliances without requiring all appliances to be on.
• Circuits can combine series and parallel arrangements.
• Two light bulbs in a series circuit dim to half their brightness compared to a single battery, but when in parallel, they maintain individual brightness.

Spectroscopy

• Certain wavelengths are absorbed as white light passes through a colored substance.
• The substance absorbs its complementary color.
• Light is comprised of photons
• Different wavelengths give different colors of light
• Different wavelengths have different associated levels of energy

Light Interactions With Matter

• Light Interacts with matter when the energy of a photon matches the energy gap between two electron energy levels.
• Visible and ultraviolet light cause valence electrons to jump to higher energy levels
• Energy conservation dictates that the absorbed photon's energy becomes stored as potential in excited electrons.
• The detector in spectrometer measures the intensity, or number of photons, which is the light before light goes through a sample (10) and after (1).
• Absorbance is parameter without units
• Number = more light being absorbed
• Current instruments use physical or chemical phenomena to an electric current.
• Devices exploit the photoelectric effect to measure light intensity.
  • A photon of light causes the detector to eject an electron.
  • The electrons move through an electric circuit.
• Generated electric current scales proportionally with both the ejected electrons and photons striking the detector.
• Percentage of light passing a sample is the "percent transmittance," or %T.

Beer's Law

• Describes intensity changes in light as it moves through a liquid.
• Light intensity decreases exponentially when passing through liquid.
• Pulse oximetry utilizes this law with an LED as this light source.

Beer-Lambert Law

• Absorptivity, concentration, and distance affect how much light is absorbed
  • Where A = absorbance.
• Absorptivity (a) is a constant for each substance, varies at each wavelength, and describes photons likelihood of molecule excitation.
• Higher concentration (c) means a greater possibility of the analyte and photon interacting
• Distant the light travels and distance (b) are proportional.
• Beer’s law states that: A = abc.

Pulse Oximetry

• Pulse oximetry’s operation depends on how Lambert-Beer or Beer's law applies to various light wavelengths and frequencies.
• Blood color is determined by oxygen saturation.
• Hemoglobin (Hgb) optical qualities vary with saturation, creating ratio differences between arterial and venous blood.
• A sensor measures the difference between red/visible light (650–750 nm for venous) and infrared light (900–1000 nm for arterial) – The device is placed on a finger, toe, or earlobe to transilluminate tissue.
  • Deoxygenated hemoglobin absorbs the visible red wavelength nm.
  • Oxygenated hemoglobin absorbs infrared light at 900-1000 nm (940 nm).
• Amount of light not absorbed measured by photodetector.
• This signal is used to calculate SAO2 or saturated Hgb by microprocessor
• Normal Conditions:
  • Pulse ox of 90 = 60 PaO2
  • 80 = 50 PaO2
  • 70 = 40 PaO2
• Low perfusion from pulse oximetry can cause burns to the measurement site because the LED gets hot
• Electrical safety combines electricity, patients, and wet conditions in operating rooms, which can lead to potential hazards

Grounding

• Electrical power is grounded is grounded in homes
• Electrical power is ungrounded in ORs.
• In homes, electrical equipment may be grounded or ungrounded, but it should always be grounded in the OR for safety.
• Current is isolated from ground potential for surgeons due to ungrounded power system
• In isolate power systems potential difference occurs only between wires

Fuses

• Fuses minimize possibilities of electrical shock
• Fuses prevent current from flowing from short/circuit overload
• Fuses use metal strips that melt when currents exceed a certain level
• Fuses use metal strips that melt when currents exceed a certain level.
• Polarized plugs use wide and narrow prongs.
• A casing is wired directly through 3-pronged grounds and protects against potential high risks
• Ground prongs should be longer to cause contact first.
• Green dots indicate where the grounding is, and the power outlet is in red
• They disrupt current imbalances.

Ground Fault Circuit Interrupters (GFCI)

• Designed for immediately disrupting current if imbalanced
• Have two additional buttons for outlet functionality testing and circuit resetting.

Power Receptacles

• Electrical systems and receptacles differ and cause incompatibility
• North America standards are set per NEMA to accidental device and power source connections.
• The NEMA 5-20 plug minimizes the possibility of plugging into 15-A due to pin rotation.
• UL tests and maintains safety.

Ungrounded Systems

• ORs use internal ungrounded circuits to help personnel and patient protection
• Power source + secondary power source coils consists of isolation AC in isolated transformer
• No direct contact between secondary and primary circuits and should not connect ground.
• No current flows if they touch wires

Line Isolation Monitor (LIM)

• A device used to signal the grounding of an ungrounded alarm
• A circuit (2 – 5mA) identifies the fault and determines fault size
• It also measures impedance in the circuit to determine the line. -To troubleshoot it needs manual equipment unplugging

Electrical Shock

• Electrical shock from 3 mechanisms:
  • Damage insulation or faulty wirings causes contact
  • Magnetic flow makes contact metal casing; flow is produced by small contact and inductance
  • AC builds up with closed circuits causes issues

Macroshock

• Large amounts of electric current though the patient's skin that can cause V fib at 100- 300mA

Microshock

• Small amounts of electric current though the patient's skin that can cause V fib at 50-100mA

• 40% of electrical accidents in hospitals are cause by surgery
• The OR has been grounded and monitored by line monitor
• Not grounded and live is on unground wiring
• Equipment casings use grounded outlets to prevent patient contact and shock.
• Follow NFPA to manage the risks involving wet locations in procedures due to operating rooms

Surgical Diathermy (Electrocautery)

• Applied tissue resistance and high frequency AC voltage
• Energy = tissue loss and heat dissipation.
• Flow must be in circuit, and the cautery dispersal is from tip to return electode
  • Patient burns from pad placement are possible.
  • Radio uses AC that is fast for use
  • Membranes do not sustain as long
  • When using on patient with AIDC + Pacemaker it is important to understand settings
    • Use a magnet to turn of device.
    • Or has external debrillator
  • Pacemaker then turns pacemaker to continuous async mode
    • Be familiar settings when you turn in back on
  • IF pace fails then remove from AIDCD and try on your own
  • Be aware sign of possible shock.
  • All metal needs to be removed
• Use return pas as distant location on pacemaker

Electrical Fires

• Fires are now just as common as 1000 years ago now that there are new flammable anesthetic agents by including technology hazards that can cause death from electrocutery.
• Open O2 is common
• Surgery above is at highest risks headneck and upper best
• 80 % is due to regional
• Fire is oxygen + fuel + oxidizing

Fire Prevention

• Air limits
• Oxidizer - 10%
• Check O2 use
• Always check for dry skin
• Use bipolar ESU
• Open areas help avoid buildup
• Moisten the source of fire
• Call personal to help department

Fire Action

• Anesthesia is required to handle
  • Lower O2 after consult from physician
  • If laser disonue oxygen use
• Keep area humid or use suction
• Carbon dioxide should be used
• High oxygen may cause pillow to accumulate it
• Humification helps prevent

N2O facts

• Colorless ordorless
• Needs oxygen to spread
• 565 F will cause oxygen
• High heat is 1110

If fire

• Stop all
• Make team do tasks
• Turn gases off
• Get water

The Mnemonic ERASE (Fire Action)

• Extinguish
• Remove
• Activare
• Shut
• Evaluate
• Quickly simutanouesly disconnect to avoid

Air Quality

• Remove ETT and stop forcerps.
• Give water, saline, ventilate, or Intuate

Laser Facts

• IV causes skin damage
• First 2-3 level caused by laser
• Can lead to ocular trauma and lose of bleeding.
• High amount of air coolant needs.
• The O2 needs to get to the barb and avoid flow.

Time Out Assessment

• All needs to be read well and understood
• Skin - 3
• Fire is high score rating

Laser Safety

• Surgery uses LASERs, and should be matched and resistance,
• Lasers should not have resistance, as it can build up heat
• Cuffs are needed, a clear vision.

Metal Issues

• Rigid is needed
• Be ventilated
• Should be high
• Need a shutdown for windows