Flashcards in Physics and Chemistry Deck (49):
The closer the vapor pressure is to atmospheric pressure, the more easily it _____.
*this is why desflurane is placed in a heated vaporizer
Vapor pressure is a function of _______.
The % concentration of any gas is found by _______.
dividing the pressure of the gas over the total pressure. (760 for 1 atm)
If halothane was added to an isoflurane vaporizer, what would happen to the delivered concentration? halothane added to sevo?
added to iso: it would be about the same because the VP of halothane is 244 and Iso is 240mmHg
added to sevo: the delivered concentration would be more than what was dialed because the VP of halothane is 244mmHg versus Sevo VP of 170mmHg
To remember what happens to a volatile agent that was added to the wrong vaporizer, just remember:
HLH= if a HIGHER VP agent is placed in a LOWER VP vaporizer, the concentration will be HIGHER
LHL= if a LOWER VP agent is placed in a HIGHER VP vaporizer, the concentration will be LOWER
Desflurane vaporizer is heated to _____. What is the vapor pressure at this temperature?
39 degrees C; approximately 2 atm or 1500mmHg
Name some units of pressure.
mmHg, cm H2O, atm, psi, kPa, bar
What is the conversions for the following:
mmHg--> cm H2O
atm--> mmHg--> psi--> kPa--> bar
1 mmHg= 1.36 cmH2O
1 atm=760 mmHg=14.7 psi=101 kPa= 1 bar
1 psi= 54 mmHg
What type of gauges measure high pressures?
measures the pressure relative to atmospheric pressure, not the absolute pressure--> when it reads 0... the pressure inside is equal to the atmosphere
"force" along a straight line
T= P x r is what law?
Law of LaPlace
as a structure expands (ie: radius increases-->cylindrical-- blood vessel), the tension (force) in the wall of the structure increases
In regards to the Law of LaPlace.... If you have a small soap bubble on one end of a straw and a large one on the other end, what will happen?
The small one will collapse because it has a greater pressure
*this is ONLY true when there is a liquid-air interface..... this happens in ARDS, when smaller alveoli collapse due to lower than normal surfactant and empty into alveoli with lower pressures--> causing atelectasis
** normal alveoli with normal surfactant--> tension would increase with the radius
According to Poiseuille's Law, doubling the radius increases flow _____ times.
tripling the radius= increases flow 81 times
halving the radius= decreases flow to 1/16th of original
Changing what single factor, according to Poiseuille's Law, has the most impact on flow?
What property of a fluid determines flow, when flow is laminar?
When does flow become turbulent?
1) velocity of flow is high
2) tube wall is rough (corrugated)
3) kinks, bends, narrowing, or branches (RAE tube)
4) fluid flows through an orifice
*does not become turbulent when flowing through an angled tube if the angle is <25 degrees
5) reynolds # exceeds 1500-2000
Resistance to flow ______ when flow becomes turbulent.
What explains why the temperature of a cylinder of compressed gas decreases as the gas is released?
How to remember the common gas laws???
Can the gay people possible b---- v-----.
What is the generalized ideal (universal) gas law?
where P= pressure, V=volume, T=temperature, n=moles of gas, and R=universal gas constant
One ____ is the molecular weight of a substance in grams.
_______ described the relationship between the amount of gas and volume of gas.
What is Avogadro's number?
the number of molecules in one mole of a substance is 6.022 x 10 to the 23rd
What was Avogadro's hypothesis?
one mole of gas at standard temperature (0C) and standard pressure (1atm) occupies a volume of 22.4 liters
2 moles of gaseous N2O occupy what volume under standard conditions?
22.4 x 2= 44.8 liters
What is critical temperature?
gases liquefy if sufficient pressure is applied and the temperature is below a critical value called the critical temperature
ex) critical temperature of N2O is 36.5C, so it can be compressed and stored as a liquid at room temperature
ex) critical temperature of O2 is -119C, O2 cannot be liquefied at room temperature no matter how much pressure is applied
heat cannot be dissipated ("constant heat")
What is the Joule-Thompson effect?
"Joule is Cool"
when compressed gas is allowed to escape freely into space, the process is adiabatic and cooling occurs (explains why condensation forms after opening a valve)
At 20C, a full E-cylinder of O2 has a pressure of ~ _______psi and contains approximately ______L.
What law is all about diffusion?
Diffusion rate of a gas is directly proportional to:______
1) partial pressure gradient
2) membrane area
3) solubility of gas in membrane
Diffusion rate of a gas is inversely proportional to:______
1) membrane thickness
2) the square root of the molecular weight
Fick's law explains what 4 clinical scenarios?
1) concentration effect
2) second gas effect
3) diffusion hypoxia
4) why turning on N2O leads to an increase in volume (or pressure) in gas spaces in the patients body
What does Graham's law explain?
why smaller substances diffuse in greater quantities (so does Fick's law)
What crosses the alveolar and capillary membrane the fastest... CO2 or O2?
CO2 diffuses 20 times faster than O2 d\t its fluid solubility
Equilibration of an inhalational agent occurs in the body when the partial pressure of the gas is _______.
the same everywhere
The process by which the fetus receives O2 and drugs is ________.
simple diffusion across the placental barrier
Diffusion of gas from alveoli to blood requires:______.
a difference in partial pressure
Agents that poorly penetrate the BBB or placental barrier have what characteristics?
1) lipid INSOLUBLE (ionized, etc)
2) large (high molecular weights)
A membrane that is impermeable to one or more solutes is said to be _________.
a semipermeable membrane
What does osmosis require?
1) semipermeable membrane
2) difference in concentration of solutes
________ that accompanies liver disease is the cause of ascites.
hypoalbuminemia---> less osmotic pressure keeping the fluid in
albumin is the major determinant of intravascular volume
Who's law explains the pulse-ox?
How is the majority of heat lost?
List the routes of heat loss from greatest to least.
1) radiation 60%
2) convection 15-30%
3) evaporation 20%
4) conduction <5%
What happens to relative humidity as temperature falls?
relative humidity increases as temperature falls because saturated vapor pressure falls
relative humidity (%)= actual vapor pressure
________________ x 100%
saturated vapor pressure
What is the partial pressure of saturated water vapor at 37C?
What happens to the air when temperature falls?
air has reduced capacity to hold water vapor, so water condenses