Exam III Flashcards
Boyle’s Law
At a constant temperature, pressure and volume are inversely related.
P1 x V1 = P2 x V2
Ex. Ambubag
Dalton’s Law of Partial Pressures
The total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.
Pt = P1 + P2 + P3 …
Ex. Calculate the partial pressure of each gas in room air.
Avogadro’s Law
Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
Avogadro’s Numbers
1 mole of gas = 6.023 x 10^23 molecules
Molar volume of any ideal gas = 22.7 L at STP
Fick’s Law of Diffusion
Accounts for molecular weight, concentration gradient, solubility, and membrane interactions (surface area and thickness).
Diffusion is directly proportional too… (3)
Difference in partial pressure
Area of the membrane
Solubility of the solute
Diffusion is inversely related to… (2)
Thickness of the membrane
Square root of the molecular weight
Graham’s Law of Effusion
The rate of effusion (gas moving through a small orifice) of a gas is inversely proportional to the square root of its molecular weight.
Ex. CO2 and O2 (CO2 is more soluble, but a larger molecule).
Henry’s Law
At a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid.
If we increase the partial pressure of a gas above a liquid, we will also increase the partial pressure of the same gas in the liquid.
p = kc
Ideal Gas Law/Universal Gas Law
Combines Boyle’s, Charles’, Gay-Lussac’s and Avogadro’s laws.
Allows us to calculate the volume for which 1 mole of a gas will expand at any given temperature or pressure.
Can be used to calculate precisely how much O2 is left in a cylinder.
Ideal Gas Law/Universal Gas Law Equation
P x V = n x R x T
P = Pressure
V = Volume
n = # of moles
R = Gas constant (0.0821 Latm/molk)
T = Temperature (kelvin)
Gas Constant
0.0821 Latm/molk
Molecular Weight of N2O
44g
Atomic weight:
N = 14
O = 16
14 + 14 + 16 = 44
Molecular Weight of O2
32
Atomic weight:
O = 16
16 + 16 = 32
Celsius to Kelvin
K = C + 273.15
Fahrenheit to Celsius
(F - 32) x 5/9 = C
Concentration Effect
N2O is 35x more soluble in blood than N
→ rapid movement of N2O across lung tissue into the blood and slow replacement of N from blood into the alveoli
→ net movement of molecules out of alveoli causes them to shrink
→ gases left behind are therefore concentrated in a smaller space.
*Boyle’s Law + Fick’s law
Second Gas Effect
Volatile agent + N2O
→ N2O rapidly diffuses
→ concentration of volatile agent increases
→ creates a larger pressure gradient from the alveoli into the blood
→ higher rate of diffusion.
Diffusion Hypoxia
Body tissue is saturated with N2O at the end of surgery.
If we do not allow enough time to replace N2O with O2 during emergence, the rapid influx of N2O into the alveoli will dilute the partial pressure of O2 in the alveoli.
If patient is placed on RA instead of 100% FiO2, the dilution of oxygen will be equal to breathing a hypoxic gas mix.
N2O Tank Calculations (>745 psi)
Utilize ideal gas law:
V = (n x R x T) / P
Ex. N2O tank has 2000g left (Current weight - tare weight)
2000g / 44 g/mole = 45.22 moles
V = (45.22 x 0.0821x 298) / 1 atm = 1111.7 L
Flow rate @ 2L / min
1111.7 L / 2 L /min = 555.85 mins / 60 = ~9.26 hours.
N2O Tank Calculations (<745 psi)
V2 = (V1 x P2) / P1
Ex. 1/4 tank = 250 L/745psi Tank psi = 620 psi
V2 = (250 x 620) / 745 = 208 L
Flow rate: 7 L / min = 208 / 7 = 29.71 mins = ~30 mins
O2 Tank Calculations
V2 = (V1 x P2) / P1
Ex. Full O2 tank = 660L/2200 psig. Tank reads 620 psig and O2 flow @ 4 L/min
V2 = (660 x 620) / 2200 = 186L / 4 = 46.5 mins
Vapor Pressure
Pressure exerted by the molecules of a liquid that have been liberated to a vapor form on the walls of a closed container at thermodynamic equilibrium.
Saturated Vapor Pressure (SVP)
Amount of pressure exerted by the vapor at equilibrium with its condensed state at a specific temperature.
The amount of pressure a vapor can exert before it returns to its liquid state.
Altitude
Increased altitude will increase anesthetic gas concentration.
Decreased altitude will decrease anesthetic gas concentration.
Anesthetic depth is dependent on partial pressure of anesthetic gas.
When atmospheric pressure decreases (increased altitude), liquids boil at lower temperatures.
Desflurane Vapor Pressure
669 mmHg
Isoflurane Vapor Pressure
238 mmHg
Sevoflurane Vapor Pressure
137 mmHg
Incorrect Volatile Agent in Vaporizer
High (VP) → Low (Vaporizer) → High (Dose)
Low (VP) → High (Vaporizer) → Low (Dose)
Ex. Sevo (137) → Iso Vaporizer (238) → Low dose
Boiling Point
Temperature the bulk of the liquid at a given pressure converts to vapor.
Occurs when the vapor pressure is greater than or equal to atmospheric pressure.
Decreased atmospheric pressure = Decreased boiling point
Ex. The higher the VP (at room temp), the lower the boiling point (Desflurane).
Partial Pressure
The pressure of an individual component in a gaseous mixture.
Solids
Materials that resist change in shape and volume
Liquids
Fluids that exhibit minimal to no compressibility and may change volume with changes in pressure and temperature.
Gases
Fluids that are compressible and easily change volume with changes in pressure and temperature.
Melting
Solid → Liquid
Evaporation
Liquid → Gas
Condensation
Gas → Liquid
Freezing
Liquid → Solid
Sublimation
Solid → Gas
Deposition
Gas → Solid
Critical Temperature
Temperature above which a substance can no longer be liquefied by the application of pressure alone.
> Critical temp → gas
< Critical temp → vapor (exists in equilibrium with the liquid phase).
Critical Pressure
Pressure required to liquefy a vapor at its critical temperature.
Heat of Fusion (enthalpy of fusion)
Amount of energy required to change a substance from a solid state to a liquid state at a constant temperature and pressure.
Occurs at the melting point.
Heat of Vaporization (enthalpy of vaporization)
Amount of heat energy required to change a substance from a liquid state to a gaseous state at a constant temperature and pressure.
Occurs at boiling point.
Law of Laplace
Relationship between pressure, radius, and tension in a spherical or cylindrical shape.
Law of Laplace: Cylinder
T = P x r
Tension is directly proportional to pressure and radius.
Radius increases → pressure decreases.
Radius decreases → pressure increases.
If radius and pressure increase → Tension increases
Ex. Blood vessels
Law of Laplace: Sphere
2T = P x r OR T = P x (r/2)
Spheres can handle x3 the pressure or radius.
Law Used to Calculate O2 Tanks
Boyle’s Law: V1 + P1 = V2 + P2
or
V2 = (V1 - P2) / P1
Coulomb’s Law
The change in potential energy caused by the movement of electrons from an area of high concentration or high charge density to an area of low concentration or low charge density.
Like charges repel.
Opposite charges attract.
Coulomb
SI unit for electric charge
The amount of electrical charge transported in one second by a steady current of one ampere.
Ohm’s Law
Potential flow of electrical charge is proportional to actual current after accounting for resistance.
V (voltage) = A (current) x O (resistance)
Ex. BP = CO x SVR
Current
How much charge is flowing past a point in a circuit in 1 second
Coulomb/sec or amperes (amps)
Beer Lambert’s Law
Lambert’s = Intensity of transmitted light decreases as the distance travelled through the substance increases.
Beer’s = Intensity of transmitted light decreases as the concentration of the substance increases.
Pulse Oximetry
Applies to Beer-Lambert law to the absorption of two specific frequencies (infrared and visible red) by hemoglobin.
Visible Red Wavelength
Absorbed by DEOXYgenated hemoglobin.
660nm
Infrared Wavelength
Absorbed by OXYgenated hemoglobin.
940 nm
Disadvantages of Pulse Oximetry (6)
Susceptible to artifact and light.
Limits with hypothermic or vasoconstricted states.
Nail polish/acrylics.
Dye interference (ICG and methylene blue).
Abnormal hgb states and erroneous values (carbon monoxide).
Risk of burns in poor perfusion states.
Causes of Electrical Injury
Direct contact with metal casing due to insulation damage or faulty construction.
Inductance due to the magnetic field of alternating current, producing a small electrical flow in the surrounding metal casing despite no direct contact.
Stray capacitance from buildup of electrical potentials with with an alternating current circuit despite no closed-circuit electrical flow.
Macroshock
Electrical shocks that traverse intact skin.
Larger amounts of current applied to the external surface of the body.
The impedance of the skin offers a higher resistance which requires a greater current to induce vfib.
DC Circuit
Direct current flow of electrons in one direction
AC Circuit
Alternating circuit
Flow of electrons reverses direction @ set frequency (60 Hz)
Line Isolation Monitor (LIM)
Device placed between the live wires and the ground to measure the impedance to flow.
Alarms if a live wire has contact or high capacitance to ground.
LIM Alarms Protocol
Alarms @ 2-5 mA
Disconnect last piece of equipment plugged into and inspect it to verify that it is the offending item.
May also be activate because of the cumulative effect of minor leakage of many piece of properly working equipment but no risk present.
Microshock
Smaller amounts of current that is applied directly to the myocardium.
Since skin is bypassed, it takes much less current to induce vfib.
What increases susceptibility to microshock?
Direct pathways:
CIV
PA catheters
Pacer wires
Macroshock threshold for perception
1 mA
Macroshock for Loss of Consciousness
50 mA
Macroshock for Vfib
100-300 mA
Microshock for Vfib
100 μA
Power units
Watts
Electrical potential units
Volts
Electrocautery
High frequency electrical currents to cauterize, cut, and destroy tissue,
Bipolar Devices
Two tips
One to supply the electrical current and the other to return the current.
Does not require a return electrode.
Less likely to cause burns or injuries apart from local area of use.
Unipolar Device
One tip
To deliver electrical current, large surface area return electrode with good conductive contact must be place on the patient (grounding pad).
Path of current flow to the ground pad must not cross the patients heart.
Considerations with Electrocautery
ECG → Artifact
Pacemakers → May sense electromagnetic conductance as inherent electrical activity and not pace
Magnet → Place on PPM to fire at asynchronous rate (ALWAYS interrogate PPM as part of pre-op assessment).
How does EMR interact with matter?
Reflected
Refracted (Scatter)
Diffracted (Redirected)
Absorbed (Interfered)
Radiation Safety
Time → Minimize
Distance → 6 feet away
Shielding → Lead
Max Dose of Radiation
5 rems / 5,000 milirems
Ionizing Radiation
Radiation capable of ionizing → the removal of an electron from an atom.
Ionizing radiation is so named because it is capable of removing an orbital electron from matter.
Causes cellular injury.
Examples of Ionizing Radiation
X rays
Gamma rays
Alpha and Beta particles
Non-ionizing Radiation
Radiation for which the mechanism of action in tissue does not involve ionization.
Examples of Nonionizing Radiation
Visible light
Infrared radiation
Microwaves
Radio-waves
MRI
Ultrasound
LASER
Light amplification by stimulated emmision of radiation.
Function of Lasers
They use a continual energizing of atoms in order to force photons that are of the same frequency and direction to be released which results in continuous production of monochromatic and unidirectional photons which can be directed into a laser beam.
Types of Lasers
CO2
Nd:YAG
Argon
Ruby
CO2 Laser Uses
Head, neck, face surgery
Airway surgeries
Longer wavelength, does not penetrate as deep into tissue
More suitable for superficial lesions or airway surgeries
Nd:YAG Laser Uses
Generalized cutting and coagulation
Shorter wavelength, greater ability to penetrate and destroy tissues.
Argon Laser Uses
Vascular lesions
Ruby Laser Uses
Retinal surgery
Laser Safety Considerations
Ignition source in presence of oxygen.
Eye protection for staff and patient
Smoke precautions
Misdirected beam
ETT Fire Protocol (8 steps)
Stop O2 flow
Stop ventilation
Disconnect circuit
Extubate patient
Extinguish fire
Mask ventilate
Reintubate
Refer for bronch, lavage, steriods
ETT Fire Prevention
Use low FiO2
Use nonflammable or shielded ETT cuff
Saline + methlyene blue in ETT cuff
Saline/sterile water on standby
Charge SI Unit
Coulombs (C)
Electrical Potential SI Unit
Volts (V)
Current SI Unit
Amperes (A)
Resistance SI Unit
Ohms (Omega)
Power SI Unit
Watts (W)
How do lasers function? (4)
Population inversion
Stimulated Emission
Stimulated Absorption
Spontaneous Emissions
How doe lasers differ from light? (3)
Monochromatic
Spatial Coherences
Collimation
