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15 Cards in this Set
- Front
- Back
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What is diffusion?
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Diffusion is the slow steady movement of individual molecules from one region to another.
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Where do gas molecules move during diffusion?
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From an area of high partial pressure to an area of low partial pressure.
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When gas diffusion takes place in the lungs, oxygen and carbon dioxide must move through what 4 barriers?
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Lung tissue, capillary wall, plasma and the membrane of red blood cells.
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What are the 3 diffusion laws?
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Fick's Law, Graham's Law, Henry's Law
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Fick's Law (formula)
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diffusion = AxDxDeltaP/T
A=Cross-sectional area D=Diffusion coefficient of a gas DeltaP=Pressure Gradient of Gas T=Lung Membrane thickness |
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Fick's Law (definition)
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Rate of diffusion of a gas is proportional to its concentration.
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Graham's Law
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Used to find diffusion coefficient for D in Fick's Law
DC=solubility coefficient(a)/square root of gmw |
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Solubility Coefficient (a)
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Lab value given to every gas
O2=.023 CO2=.51 |
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Henry's Law
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At a given Temp, the volume of a gas that dissolves in a liquid (V) is directly related to its solubility coefficient (a) multiplied by its partial pressure (Pgas).
V=AxPgas Predicts how much of a gas will dissolve in a liquid. |
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Flow
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the movement of a volume of fluid per unit of time
L/sec L/min |
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Velocity
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Measure of linear distance traveled by the fluid per unit of time
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Bernoulli's Principle
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If driving pressure is constant, as gas flow meets a narrowing or restriction the molecules speed up with increasing forward velocity.
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Why the increase in velocity in Bernoulli's Principle?
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b/c the same # of molecules are trying to get through the narrowed opening in a given amount of time.
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Why is there a drop in lateral pressure w/ the increase in velocity? What happens b/c of it?
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The increased velocity causes the molecules to move faster, they spend less time hitting the walls of the tube, thus a drop in lateral pressure.
Drop in lateral pressure causes a vacuum or sucking action that can be used to entrain (bring in) additional fluid. |
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Venturi Tubes and Mask
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Venturi Tube is a modification of the Bernoulli Principle.
V.T. - Widens just after the jet port and helps keep the FiO2 constant by restoring the pressure and flow b ack toward the set values found before the narrowing. The angle of widening has to be less than 15deg to restore pressure and flow. |
