5) Gas Laws

Question 1

Boyles Law

Answer 1

• pressure and volume inversely proportional
• ambu bag is example
• SV example

Question 2

Charles Law

Answer 2

• temp and volume are directly proportional

- LMA cuff ruptures in autoclave

Question 3

Gay Lussac’s Law

Answer 3

• Temperature and Pressure are directly related

- increase temperature increase vapor pressure

Question 4

Avogadro Law

Answer 4

• N directly proportional to

Question 5

Application of Ideal Gas Law

Answer 5

• as a cylinder of compressed gas empties, the pressure falls

Question 6

Gas solubility in liquids ___ related to temp and _____ related to pressure

Answer 6

Inversely (hypothermic patients slow to wake up)

Directly (nitrous oxide in the ecylinder)

Question 7

Henry’s Law

Answer 7

• 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

Question 8

Application of Henry’s Law

Answer 8

• increasing FiO2

Question 9

Graham’s Law

Answer 9

• a gas diffuses at a rate that is inversely proportional to the square root of its molecular weight
• higher weight, slower rate of diffusion

Question 10

Application of Graham’s Law

Answer 10

• nitrous oxide diffusing into air filled cavities such as an ETT cuff

Question 11

Fick’s Law

Answer 11

-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

Question 12

Application of Ficks Law

Answer 12

• gas exchange across the alveoli

- second gas effect (volume of nitrous oxide diffusing IN is > than volume nitrogen moving OUT)

Question 13

Pressure Units

Answer 13

1atm = 14.7 psi = 760 mmHG = 760 torr = 1 bar = 1020cm H2O

Question 14

Adiabatic Cooling

Answer 14

• 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

Question 15

Joule-Thompson Effect

Answer 15

• expansion of gas causes cooling

- as gas leaves cylinder, the expansion cools creating condensation of moisture on cylinder

Question 16

Poiseuille’s Law

Answer 16

• 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

Question 17

Viscosity and Density and Reynolds #

Answer 17

Viscosity determines laminar flow at low flow rates (low flow O2)
Density determines turbulent flow at high flow rates (ex. Heliox)

Question 18

Reynolds Number

Answer 18

R = velocity x density x diameter / viscosity

Question 19

What factors change flow from laminar to turbulent?

Answer 19

-increased velocity, bend >20 degrees, irregularity in the tube

Question 20

Bernoulli’s Theorem

Answer 20

• 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

Question 21

Law of LaPlace

Answer 21

-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

Question 22

Ohms Law

Answer 22

-V = IR
-voltage = current x resistance
-ex pressure transducer
Pressure current creates voltage in an ABG waveform

Question 23

Macro shock vs micro shock

Answer 23

• macroshock is the current distributed through the body (improper grounding)
• microshock is the current applied in or near the heart