PPT 5 Fluids Flashcards by Felicia Woodall

What defines a fluid?

material that has the ability to flow

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what states of matter are considered fluids?

liquids and gases

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hydrostatics

is the study of fluids that are not moving.

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hydrodynamics

is the study of fluids in motion

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Venturi effect and/or bernoulli principle

When fluid flow through a constricted region of a tube, the velocity of fluid increases and lateral pressure decreases. (lateral pressure exerted by the fluid on the walls of the tube)

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applications (examples) of the bernoulli principle and/or Venturi effect.

The Venturi oxygen mask, nebulizer, jet ventilator and injectors.

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Laminar flow

streamlined, in a straight line.

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What law describes laminar flow.

Poiseuille’s law

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What is flow directly proportional to?

fourth power of radius (r)

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is flow through large bore needles faster or slower than flow through small bore needles?

Flow through large bore needle is faster than small bore needle

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Flow is directly proportional to?

gradient change in pressure.

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Flow is inversely proportional to? (choose two)

fluid viscosity and

length of the tube

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viscosity and flow in polycythemia?

increased viscosity, therefore decreased flow.

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viscosity and flow in anemia?

decreased viscosity, therefore increased flow.

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vessel diameter is also called?

radius

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The relation between vessel diameter ( or radius) and resistance is?

Inverse, if one goes up the other will go down.

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The greater the radius then the smaller or larger the resistance?

smaller

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to what power of the radius is resistance inversely proportional?

radius (r) to the fourth power.

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If a vessel has twice the length of another vessel but the same radius then?

The twice as long vessel will have twice the resistance to flow.

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If the viscosity of the blood increases by 2 fold then the resistance to flow will increase by how much?

2- fold

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Will an increase in radius reduce or increase resistance?

it will reduce resistance with an increase in radius.

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change in radius alters resistance to the ? power of the change in radius.

fourth

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a 2-fold increase in radius decreases resistance by how much?

16-fold

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vessel resistance is very sensitive to change in what?

radius

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formula for resistance to flow (laminar flow) (there are technically two formulas)

``` R= change P/F R= 8nl/pie r^4 ```

increasing radius of a needle or catheter on an IV can ? flow.

increase flow

Smaller gauge numbers on an IV indicate?

larger diameters

Selecting a needle with a shorter length can increase or decrease flow through an IV line?

increase

If you increase the height of the IV bag then it ?

increases the hydrostatic pressure in the IV bag.

How do you apply poiseuille's law while transfusing packed RBCs?

Large diameter IV catheter, pressure bag and dilution by adding normal saline.

what happens to your blood flow in polycythemia?

sluggish flow due to increase viscosity of blood.

what happens to your blood flow in anemia?

increased blood flow due to decreased viscosity of blood.

larger the endotracheal tube, what happens to the flow of gas?

the flow is better (more radius)

anything that increases diameter of the airway is going to help with better flow, what is a medication that increases diameter of the airway?

Beta 2 agonist increase diameter of the airway.

increasing peak inspiratory pressure leads to?

increased gradient which leads to increase delivery of tidal volume.

Flow becomes turbulent if?

1. Velocity of flow is high 2. Tube wall is rough 3. Kinks, bends, narrowing or branches in the tube. 4. Fluid flow through orifice.

Laminar flow does not become turbulent when fluid is flowing through an angled tube if the angle is less than?

25 degrees

Does resistance to flow increase or decrease when flow becomes turbulent?

resistance to flow increases when flow becomes turbulent which leads to difficult ventilation.

What formula predicts whether flow will be laminar or turbulent.

Reynolds number (Re)

Reynolds number is directly proportional to?

fluid velocity, tube diameter (d), and fluid density (p)

Reynolds number is inversely proportional to?

fluid viscosity (n)

flow will become turbulent if ?

velocity gets high enough (narrowing of a vessel)

When reynolds number is greater than ???, flow will change from laminar to turbulent?

greater than 1500-3000 flow will change

When flow is turbulent what factor determines flow?

density (p) NOT viscosity.

What affect do low density gases have on breathing (needed when someone is having an asthma attack)

they make breathing easier

Name a low density gas we use in the OR?

Helium (He)

helium/oxygen gas mixture is known as?

Heliox

Whats special about Heliox when used during a severe asthmatic attack when the obstruction is causing flow to be turbulent?

heliox decreases work of breathing and restores laminar flow (because it is a low density gas)

Flow is inversely proportional to? (when talking about turbulent flow)

density

What are bruits?

Turbulent flow causes audible vibration called bruits

Causes of turbulent blood flow? (4 examples)

High velocities Sharp turns in the circulation Rough surfaces in the circulation Rapid narrowing of blood vessels

Turbulence is increased by?

decreased Blood viscosity (e.g. decreased crit, anemia) increased Blood velocity (e.g. narrowing of vessel)

Who has the lower density helium or nitrogen?

Helium

What is the Coanda Effect?

Tendency of fluid flow to follow a curved surface upon emerging from a constriction This may cause preferential flow in one tube at a bifurcation

If a constriction occurs at a bifurcation what will then occur? eventually leading to maldistribution.

Constriction occurs at bifurcation then increase velocity and decrease pressure thus fluid will stick to the side of branch leading to maldistribution

What can a mucus plug cause if it occurs at the branching of the respiratory tree?

maldistribution of respiratory gases.

What can cause unequal blood flow in the arteries?

Atherosclerotic plaque

Formula for pressure in a fluid?

P=pgh | Pressure = density x acceleration due to gravity x height

nonstandard but fairly common "pressure" units in terms of mass per area?

g/cm^2 N/m^2 is the standard metric unit of pressure.

The pressure at any depth of a fluid can be calculated if? (if you know 2 other things)

you know the pressure at some other depth and the density of the fluid.

at a given depth in a fluid that fluid exerts what kind of pressure in all directions?

the same pressure in all directions

Does the container a liquid is in have any effect on the pressure?

pressure is independent of container shape.

True or false Pressure applied to a confined fluid will increase pressure throughout the fluid by the same amount?

TRUE, if you increased pressure on top of a confined fluid by x amount then x amount pressure everywhere in the fluid goes up.