## Glossary of Physics of anesthesia

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- that which tends to change the state or motion of an object
- force

- 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
- laminar

- 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
- density

- in laminar flow, as this fluid property decreases, flow increases
- viscosity

- type of flow usual in lower respiratory tract
- laminar

- type of flow usual in upper respiratory tract
- turbulent

- 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
- surfactant

- 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
- tension

- 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
- azeotrope

- pathway with length greater than width
- tube

- pathway with width greater than length
- orifice

- 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
- osmole

- 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
- density

- tendency toward turbulence decreases when this fluid property is increased
- viscosity

- 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