5) Gas Laws Flashcards
Boyles Law
- pressure and volume inversely proportional
- ambu bag is example
- SV example
Charles Law
- temp and volume are directly proportional
- LMA cuff ruptures in autoclave
Gay Lussac’s Law
- Temperature and Pressure are directly related
- increase temperature increase vapor pressure
Avogadro Law
- N directly proportional to
Application of Ideal Gas Law
- as a cylinder of compressed gas empties, the pressure falls
Gas solubility in liquids ___ related to temp and _____ related to pressure
Inversely (hypothermic patients slow to wake up)
Directly (nitrous oxide in the ecylinder)
Henry’s Law
- at a constant temp: the amount of gas is directly proportional to partial pressure of the gas in the solution
O2 coefficient = 0.0031
CO2 coeffient = 0.067
CO2 is 25x more soluable in blood than O2
Application of Henry’s Law
- increasing FiO2
Graham’s Law
- a gas diffuses at a rate that is inversely proportional to the square root of its molecular weight
- higher weight, slower rate of diffusion
Application of Graham’s Law
- nitrous oxide diffusing into air filled cavities such as an ETT cuff
Fick’s Law
-diffusion of a gas across a semipermeable membrane is
-directly proportional to:
partial pressure gradient, membrane solubility, and solubility of the gas, and membrane area
-inversely proportional:
the membrane thickness and molecular weight
Application of Ficks Law
- gas exchange across the alveoli
- second gas effect (volume of nitrous oxide diffusing IN is > than volume nitrogen moving OUT)
Pressure Units
1atm = 14.7 psi = 760 mmHG = 760 torr = 1 bar = 1020cm H2O
Adiabatic Cooling
- occurs when a substance changes temp of matter but has no gain or loss of energy
- ex. Nitrous cylinder opens and fros forms on outside
Joule-Thompson Effect
- expansion of gas causes cooling
- as gas leaves cylinder, the expansion cools creating condensation of moisture on cylinder
Poiseuille’s Law
- describes relationship between rate and flow
Directly proportional to pressure gradient across tube and radius4
Indirectly proportional to length and viscosity
Example: IVF resuscitation a more viscous fluid would run at a slower rate, and if the length of the tube is longer (CVC vs PIV) it would run slower; if the pressure gradient was higher it would run faster (pressure bag), if the diameter was doubled it would increase by 16x
Viscosity and Density and Reynolds #
Viscosity determines laminar flow at low flow rates (low flow O2)
Density determines turbulent flow at high flow rates (ex. Heliox)
Reynolds Number
R = velocity x density x diameter / viscosity
What factors change flow from laminar to turbulent?
-increased velocity, bend >20 degrees, irregularity in the tube
Bernoulli’s Theorem
- relates how pressure and velocity interact
- narrow diameter has decreased lateral wall pressure increased velocity
- wider diameter has increased lateral wall pressure decreased velocity
- ex: Venturi tube; as the tube narrows, velocity increase and wall pressure decreases
- ex: Venturi mask
Law of LaPlace
-Transpulmonary Pressure = 2xtension / radius
Directly proportional to the surface tension
Inversely proportional to the radius
-hydrogen bonds cause water to thin
-thinner walls increase stress more apt to collapse
-surfactant increases water layer, increasing surface tension
-As the radius decreases compliance decreases
-more pressure is needed
Ohms Law
-V = IR
-voltage = current x resistance
-ex pressure transducer
Pressure current creates voltage in an ABG waveform
Macro shock vs micro shock
- macroshock is the current distributed through the body (improper grounding)
- microshock is the current applied in or near the heart
