What is the major difference between a gas and a vapor
A vapor may be liquefied by pressure without cooling, a gas cannot
What is PSI? What is Psig?
PSI = pounds per square inch
Psig = pounds per square inch gauge (takes atmosphere into consideration)
example: at sea level your anesthesia gauge is set at 0 Psig, but the atmospheric pressure around the gauge is 14.7 PSI
What is Newton's first law?
An object at rest or moving at constant velocity in a straight line will continue in the state until an external force acts upon it
What is vapor pressure?
At equilibrium, the pressure exerted by molecular collisions of gas against the container walls is the vapor pressure
Describe the mechanism inside the Bourdon gauge
- within the gauge is a thin-walled metal tube, somewhat flattened and bent into a C
- attached to its free end is a lever system that magnifies any motion of the free end of the tube.
- on the fixed end of the gauge is a fitting you thread into a boiler system
- as pressure increases within the boiler, it travels through the tube. like the snakelike paper whistle, the metal tube begins to straighten as the pressure increases inside of it
- as the tube straightens, the pointer moves around a dial the indicates the pressure in PSI
What is a manometer?
A monometer is a device calibrated to measure pressure. Come in different configurations: open, closed, aneroid manometers
Gas pressures are also known as....?
What is atomic weight?
atomic weight is the weight of each individual atom
Describe what happens when you increase the temperature of a gas
Causes an increase in kinetic energy of the gas, which in turn leads to an increase in molecule strikes against against the container, thus increasing the pressure.
Which gas law is this: Gases stored in metal cylinders, if the temp of the cylinder is increased, the pressure inside the cylinder will increase, even though no gas has been added to the cylinder
Gay-Lussac's Ideal Gas Law
What will happen when a volatile liquid resides in a closed container?
The molecules of the substance will equilibrate between the liquid and gas phase
produced by a gas within a container is a result of the collision of gas molecules with the wall of the container
pressure = force/area
Ideal gas law is also known as...
Common gas law
Density of a gas is also known as...?
Gram molecular volume
What are the CONSTANTS in Boyle's gas law, Charles' gas law, and Gay-Lussac's Gas law?
Boyles = Temperature
Charles = Pressure
Gay-Lussac = Volume
What is an ideal gas?
- Highly rarefied gas, one in which the molecules are extremely far apart
- No attraction between the molecules
- Ideal gases do not actually exist
Describe Gay-Lussac's Ideal Gas Law
as temperature increases there is an increase in the rapid molecular motion of gas molecules increasing the frequency of molecules hitting the 'container' in which they are stored in and subsequently increases the pressure measured
What is standard condition and SATP?
Standard temperature and Pressure (STP) is 0 degrees celsius at 760mmHg (1atm)
Standard ambient temperature and pressure denotes a reference temperature of 25 degrees celsius and 760mmHg (1atm)
Describe Charles' Ideal Gas Law
- volume of gas at a CONSTANT pressure varies DIRECTLY with absolute temperature (changing temperature)
- only works in an environment where volume can move; container can expand
- (V1/T1) = (V2/T2)
- To double pressure increase temp by 273 degrees
- A given quantity of gas, kept at constant pressure expands by 1/273 of its volume at 1 degree celsisus for each degree rise in temperature
Real gases deviate strongly from ideal behavior at high ___________ and/or ____________ temperature
High pressure, low temperature
Describe Avogadro's Hypothesis
- one mole of a gas at standard temperature and standard pressure occupies of a volume of 22.4 liters
The amount of gas dissolving in a liquid will _____________ as temperature rises
Vapor pressure is dependent on...
Temperature and the physical characteristics of the liquid
What is a barometer and who invented it?
An instrument for measuring atmospheric pressure
Invented in 1643 by the Italian scientist Evangelista Torricelli, who used a column of water in a tube 34 ft long. The water column was soon replaced by mercury, which only requires a 3ft tube
If a tank of compressed gas at 0 degrees celsius had a pressure of 2200 PSI, what would the pressure be in the tank if it were placed in a room that was 20 degrees celsius?
(20 degrees X 1/273) x 2200 PSI = (0.073) x 2200 psi = 161.17 PSI
161.17 + 2200 = 2361.17 PSI
Vapor pressures of desflurane, sevoflurane, isoflorane
The amount of matter in an object. From a physics perspective, mass can be defined as the resistance of an object to acceleration.
What is Wood's Metal?
a fusible alloy that becomes liquid at approximately 70 degrees celsius (158 degrees F). contains BLT with Cheese
What is gram molecular volume?
- volume at std conditions is equal for all gases and is 22.4 liters per mole of the known gas
- The ratio of the gases molecular weight to its volume
32g/mole/22.4l/mole = 1.429g/L
1 liter of O2 will weigh 1.429g
What is Newton's third law?
For every action, there is an equal and opposite reaction
(you push an object, the object is pushing back on you)
Describe Boyle's Ideal Gas Law
- at a CONSTANT temperature, a decrease in volume of a gas results in an increase in the pressure of a gas
- increased pressure because less space that the gas is in
- during expiration, intrapulm pressure increases and volume decreases
- squeezing breathing bag on circuit, decrease vol of gas in bag, increase of pressure within the bag causing gas to flow from breathing bag (high pressure) to lungs (low pressure)
What is Newton's second law?
F = ma
Force is equal to mass times acceleration
What is barometric pressure?
the molecules of gases composing the atmosphere exert a pressure on all earthly surfaces.
The molecules close to the surface of the earth are compressed by those above them.
One atmosphere of pressure (1atm) = 760mmHg at sea level
Describe what happens when you decrease the temperature of a gas
reduces kinetic energy, reducing molecule strikes, and decreases pressure
The ideal gas law is based on three tenets, what are they?
- gas molecules are in constant, random motion
- molecules in the sample show a range of kinetic energies, but the avg kinetic energy depends on the temperature
- no attractive or repulsive forces between the gas particles, so all collisions are elastic
what is the ideal gas law equation?
PV = nRT
p = pressure
v = volume
n = number of molecules (or moles, AKA Avogadro's #)
R = constant for all gases, approaching ideal behavior
T = temperature
What is the vapor pressure of water vapor in the alveolar gas at normal body temperature
Ideal gas laws examine the relationship between what three components?
Volume, temperature, pressure
Avogadro did NOT come up with his 'number' but how did he come up with the idea of it?
- Knew that pressure was the result of molecules of gas striking the container's walls
- molecules of gas at a given temperature all have the same velocity
- therefore, the number of molecules in equal volumes of gas must be the same
- the molar volumes of all gases should be the same
What is a vapor?
The gaseous state of matter that mostly appears as a liquid in nature.
Gaseous aggregate of molecules
Formula for pressure, and unit of measure
Pressure = Force/ Surface Area
What is Avogadro's Principle?
Equal volumes of gases under the same conditions of temperature and pressure contain the same number of molecules.
6.023x10^23 molecules ar in ONE MOLE of ANY substance
Gay-Lussac's Law: each 1 degree change in temperature will yield...
a 1/273 increase or decrease in the pressure of the given gas (starting for 0 degrees celsius)
Gas diffusing into the cuff of an LMA is an example of what gas law?
What is a bourdon gauge used for?
Used to measure high pressure (clinker pressures), gauze pressures measure the pressure relative to atmospheric pressure, not the absolute pressure.
When the gauge pressure reads zero, the pressure in the cylinder is the same as atmospheric
What is gram molecular weight?
- molecular weight of a compound expressed in grams is referred to as the gram molecular weight (which equals one mole of a substance)
- oxygen (diatomic) has a molecular weight of 32
How much space will one gram (molecular weight), or one mole occupy
Pressure alone will not cause a ________ to liquefy; heat must be ____________ in order for a liquid to be formed
Relate critical temperature to gases
Gases liquefy if sufficient pressure is applied and the temperature is below a critical value, called the critical temperature
What are the critical temperatures for Nitrous Oxide and Oxygen?
N2O = 39.5 degrees Celsius --> means that N2O can be compressed and stored as a liquid at room temperature
O2 = -116 degrees Celsius --> CANNOT be liquefied at room temperature, no matter how much pressure is applied
Why can't a tank of liquid oxygen be used in the OR?
at room temp, oxygen is above its critical temperature, and therefore a gas. Above critical temperature a gas cannot be condensed into liquid despite how much pressure is applied
What is critical pressure? What is oxygen's critical pressure?
The pressure necessary to cause liquefaction at the critical temperature
- Oxygen -116 degrees Celsius at 49.6 atm
Define saturated vapor pressure
- during the process of evaporation in a closed container there will become a point (equilibrium) where there are the same number of molecules returning tot he liquid as there are escaping the liquid.
Function of the temperature of the system, NOT the ambient pressure of the system
at sea level, isoflurane vapor and oxygen are at equilibrium in a container, what is the partial pressure of oxygen?
760 - 238 (vapor pressure of iso) = 522 mmHg of oxygen
- process by which molecules intermingle as a result of their kinetic energy of random motion
- diffusion is passive, cannot be stopped/controlled/reversed
- net action of matter, heat, momentum, or light whose end is to minimize a concentration gradient
- spontaneous process
- can only occur in one direction (from high conc to low conc)
what is the direction of diffusion determined by?
the differences in partial pressures and not by any differences in the amount of gas (or concentration gradient)
4 Factors that affect diffusion through a living membrane
1) solubility of the gas in the constituents of the membrane
2) the thickness of the membrane
3) permeability of the membrane
4) velocity of the membrane
3 mechanisms by which diffusion occurs through a cell membrane
1) directly through the lipid bilayer of the cell membrane
2) through protein channels within a membrane
3) by reversible binding to carrier proteins that can traverse the membrane
The diffusion rate of a gas is DIRECTLY proportional to (3 things)
1) partial pressure gradient of the gas
2) membrane area (larger membrane = better)
3) solubility of the gas in the membrane
The diffusion rate of a gas is INVERSELY proportional to:
1) membrane thickness
2) square root of the molecular weight (heavier = more kinetic energy/heat to move large molecule
The rate that a gas diffuses within a space or across a membrane is governed by ________'s Law and __________'s Law
Fick's Law and Graham's Law
Describe Fick's Law of Diffusion
- the RATE of diffusion of a substance across unit area (such as surface or membrane) is proportional to the concentration gradient of each gas
- higher concentration --> faster diffusion
- only applies to a single homogenous phase
Describe Graham's Law of Diffusion
- the rate of diffusion of a gas is INVERSELY PROPORTIONAL to the square root of either the density or the molar mass of the gas
- applicable only under comparable conditions of temperature and pressure
- diffusion of individual molecules. molec wt of water = 18, molec wt of alcohol = 56 --> water diffuses faster than alcohol
N2O is more soluble in blood than N2...how much more soluble is it?
34x more soluble.
What are the cardiovascular and respiratory effects of Nitrous Oxide?
- slightly stimulates SNS
- less depression than with volatiles
- less resp dep than with volatiles
- inhibits hypoxic and CO2 ventilatory drive but does not increase PaCO2
- increases in pulm vascular resistance are exaggerated in pts with pulm HTN
What are the disadvantages of nitrous oxide?
- increases volume or pressure in internal gas spaces
- limits use of higher O2 partial pressures
- produces diffusion hypoxia
- stimulates pulm stretch receptors, leading to increased resp rate
- may increase muscle tone
- long-term admin --> neuro injury, aplastic anemia, death, enzyme inhibitor (see other card about that)
- greenhouse gas stuff
nitrous oxide is an enzyme inhibitor. describe the effects of this
- inactivates the thymidylate synthetase leading to congenital anomalies
- inhibits methionine synthetase by oxidizing the cobalt atom of vit b12, leading to peripheral neuropathy from chronic abuse
- long-term use can lead to bone marrow suppression
What is tension?
when equilibrium is established between the dissolved gas in the liquid and the undissolved portion of gas overlying the liquid. the gas molecules within the liquid exert the SAME PRESSURE as the gas molecules overlying the liquid - THIS IS TENSION
The solubility of gas in a liquid depends upon...
the pressure of the gas overlying the liquid
What remains constant in Henry's Law?
Describe Henry's Law
- with temp remaining constant, the solubility of a gas in liquid is directly proportional to the partial pressure of the gas overlying the liquid
- OR quantity of gas (# of molecules) dissolved in liquid varies directly with the partial pressure of the gas overlying the liquid.
- the higher the inspired O2 tension, the higher the partial pressure of O2 in the blood
PaO2 values (40-60) and correlating % Hgb sat
PaO2 40 = 70% Hgb Sat
PaO2 50 = 80% Hgb Sat
PaO2 60 = 90% Hgb Sat
What is the solubility coefficient
refers to a volume (cm^3) of a vapor or a gas that dissolves in 100ml of solvent (water of blood)
Describe the effects of temperature on solubility
- less gas dissolves in a liquid as the temperature rises
- as a glass of drinking water is allow to warm to room temp, small bubbles are noted to form along the sides of the glass. demonstrates that water is not able to hold the gas in solution any longer
- as an anesthetized pt becomes more hypothermic, more anesthetic gas becomes dissolved in their blood