Exam III Flashcards
(99 cards)
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.