Glossary of Physics of anesthesia

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that which tends to change the state or motion of an object
SI unit of force
newton (N)
force that will accelerate one kilogram one meter per second
one newton (1 N)
SI unit of pressure
pascal (Pa)
pressure of one newton acting over one square meter
one pascal (1 Pa)
approximate atmospheric pressure at sea level
1 bar
100 kPa
760 mmHg
760 Torr
14.5 psi
1 atm
1033 cm H2O
relationship of pressure to force
P = f/a
where P = pressure
f = force
a = area
type of flow in which fluid has no eddies or turbulence
where laminar flow through a tube is fastest
center of tube
required to drive fluid through a tube
pressure differential
Hagen-Poiseuille equation
Q = (π P d^4) / (128 η l)
where Q = flow
π = 3.14...
P = pressure
d^4 = tube diameter raised to the 4th power
η = viscosity
l = tube length
equation which describes the effect of pressure, tube length/diameter, and viscosity on laminar flow
Hagen-Poiseuille equation
index which estimates the onset of turbulent flow
Reynolds number (cutoff is 2000)
Reynolds number equation
Reynolds number = vρd/η
where v = linear velocity
ρ = density
d = tube diameter
η = viscosity
a decrease in this fluid property decreases the tendency toward turbulent flow
in laminar flow, as this fluid property decreases, flow increases
type of flow usual in lower respiratory tract
type of flow usual in upper respiratory tract
Laplace's law for sphere
P = 2 X T / r
where P = pressure
T = surface tension
r = radius
its presence results in surface tension increases as alveoli distend and decreases as alveoli contract
fall of pressure at a constriction in a tube
Bernoulli effect
tube which takes advantage of Bernoulli effect to entrain gases or nebulize liquids
Venturi tube
tendency of stream of fluid or gas to continue to flow along a convex surface
Coanda effect
states that at constant temperature the volume of a given mass of gas varies inversely with the pressure
Boyle's Law
Boyle's Law equation
P ∝ 1/V
where P = pressure
V = volume
states that at constant pressure the volume of a given mass of gas varies directly with the temperature
Charles' Law
Charles' Law equation
V ∝ T
where V = volume
T = temperature
states that at constant volume the pressure of a given mass of gas varies directly with the temperature
Third Perfect Gas Law
OR Gay Lussac's Law
Third Perfect Gas Law equation
P ∝ T
where P = pressure
T = temperature
a change in the volume and pressure of the contents of a system without exchange of heat between the system and its surroundings
adiabatic change
states that in a mixture of gases the pressure exerted by each gas is the same as that which it would exert if it alone occupied the container
Dalton's Law of Partial Pressures
states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules
Avogadro's hypothesis
Avogadro's number
6.022 X 10^23
Universal Gas Constant equation
PV = nRT
where P = pressure
V = volume
n = moles
R = constant
T = temperature
temperature above which a gas cannot be liquified however much pressure is applied
critical temperature
vapor pressure of a substance at its critical temperature
critical pressure
critical temperature at which a gas mixture may separate into its constituents
pseudocritical temperature
process in which the rate of change of a quantity at any time is proportional to the quantity at that time
exponential process
the time a process would have been complete had the initial rate of change continued
time constant
relationship of time constant to half-life
half-life = time constant X 0.693
partial pressure of a vapor in a closed container and at equilibrium with the liquid phase
vapor pressure
states that at a particular temperature the amount of a gas dissolved in a liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid
Henry's Law
the volume of a gas which dissolves in one unit volume of a liquid at the temperature concerned
Ostwald solubility coefficient
the ratio of the amount of substance present in one phase compared with another the two phases being of equal volume and in equilibrium
partition coefficient
another word for partial pressure for gases in a solution
a substance in its gaseous phase above its critical temperature
a gas
a substance in its gaseous phase below its critical temperature
a vapor
Dalton's Law equation
Pmixture = P1 + P2 + P3...
fall of alveolar oxygen concentration as a result of the dilution of alveolar oxygen by excretion of nitrous oxide
diffusion hypoxia
increase in concentration (partial pressure) of a gas in the alveoli when a more soluble gas diffuses quickly into the bloodstream - results in increased rate of diffusion for the second gas
second gas effect
point at which 50% of patients cease to move in response to a stimulus
MAC (minimum alveolar concentration)
rate of diffusion of a substance across a surface or membrane is proportional to the concentration gradient
Fick's Law
states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight
Graham's Law
states that depression or reduction of vapor pressure of a solvent is proportional to the molar concentration of the solute
Raoult's Law
a mixture which vaporizes in the same proportions as the volume concentrations of the components in solution
pathway with length greater than width
pathway with width greater than length
point at which increased pressure results in turbulent flow but below which flow is laminar
critical point
variable orifice flowmeter
Thorpe tube
contributors to body pH according to Stewart
1) partial pressure of CO2
2) strong ion difference
3) total weak acids
strong ions according to Stewart
K, Na, Cl, lactate
weak acids according to Stewart
albumin, phosphate
effect of decreasing the strong ion difference on body pH according to Stewart
decreases pH
property of He which makes it useful for decreasing resistance to flow through narrowed lower airways
low density
force per area of molecules in a liquid as they interface with the gas above it
vapor pressure
a compressed gas is any mixture or material having in a container at least one of these
1) >104 psia @ 130F
2) >40 psia @ 70F
3) >40 psia @ 100F for any liquid flammable material
to determine time left on a cylinder of nitrous oxide, you must determine the volume of gas available from both...
the liquid phase and the vapor phase
unit of measure for osmotic activity
6.02 X 10^23 particles of dissolved solute that cannot diffuse through a semipermeable membrane
1 osmole
pressure exerted by 1 gmw of a nonionizing, nondiffusible solute in 22.4L of water
1 atm
pressure exerted by 1gmw of a monovalent, ionizing, nondiffusible solute in 22.4L of water
2 atm
states that even in isolation from the environment, a gas cools when expanded and warms when compressed
Poisson adiabatic equation
Which of the following does NOT affect rate of laminar flow? pressure gradient, fluid viscosity, tube length, fluid density, tube diameter
fluid density
At low rates of flow, the orifice of a variable orifice flowmeter is more like what?
a tube
tendency toward turbulence increases when this fluid property is increased
tendency toward turbulence decreases when this fluid property is increased
As tube diameter is doubled, rate of flow _________ by a factor of _____.
increases, 16
As tube length is halved, rate of flow ____________ by a factor of _____.
increases, 2

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