Mod 16: Scientific Foundations

What is matter?

composition of the universe and may be solid, liquid, gas

What is a gas?

a fluid, and is compressible and easily changes volume with changes in pressure and temp

What is a liquid?

a fluid that exhibits minimal to no compressibility, and may change volume with changes in pressure and temp

What is a solid?

a material that resists changes in shape and volume

What do fluids constantly do?

change shape and move

What are shape and movement determined by?

• gravity

• pressure

• friction

  • viscosity

What is an example of high viscosity?

Honey is more viscous than water

What are the 3 types of fluid flow?

1. laminar

2. turbulen

3. transitional

What is laminar flow?

flow in which all molecules of a fluid travel in parallel path within the tube

In laminar flow, molecules in the center of the tube …

move the fastest

Where is laminar flow seen in the body?

in the smallest airways (terminal bronchioles)

What is turbulent?

irregular, chaotic flow

• exhibited when vasculature makes sharp turns

What is transitional flow?

a mixture of laminar and turbulent

• turbulent in the center

fluid flow

What does Poiseuille’s Law describe?

flow

When is the formula for Poiseuille’s Law?

F =(πr⁴ x ∆P) / (8nL)

What are the variables for Poiseuille’s Law?

• F = flow (sometimes written as Q)

• R = radius

• ∆P = change in pressure

• N = viscosity

• L = length of tube

what does Poiseuille law show?

***Radius will have the greatest impact on flow***

Doubling the radius has a …

16 fold increase in flow (r⁴)

What are clinical applications of fluid flow?

IV gauges

RBCs

Pressure bags

Length of PIVs

What does Reynold’s Number use?

Poiseuille’s Law AND factors in the fluid’s density to determine if the flow is laminar or turbulent

What Reynold’s number is laminar flow?

<2000

In Reynold’s number, the higher the number…

the more turbulent the flow.

What is the formula for Reynold’s Number?

(vpd)/n

What is the variable for Reynold’s Number?

(vpd)/n

• V = linear velocity of the fluid

• P = density of the fluid (**density=mass/volume)

• D = diameter of the tube

• N = viscosity

What is velocity?

the rate at which an object changes

What is Bernoulli’s principle?

describes the effect of fluid flow through a constriction in a tube (narrowed area in the tube)

What does Bernoulli’s principle explain?

as flow passes through the narrowing, the velocity of that flow increases and the pressure in the are decreases

Bernoulli’s Principle: the pressure must …

drop when velocity increases due to the conversation of energy

When is Bernoulli’s principle useful?

with metered dose inhalers

What does the venturi effect utilize?

the pressure drop across a narrowing in a tube → concept of Bernoulli’s Principle

Venturi Effect

When a hole is put in the narrowed area of a tube, air is allowed to be entrained and enter the flow

Clinical application of the venturi effect?

nebulizers, venturi masks

What is the Coanda effect?

explains that fluid flow tends to follow a curved surface upon exiting the narrowed area in a tube

What is the Coanda effect the opposite of?

Bernoulli’s principle

What does Laplace’s Law describe?

the relationship of wall tension (T) to pressure (P) and radius in cylinders and spheres

What is tension?

a stress force exerted over a given area

What does Laplace’s Law explain clinically?

why smaller-diameter capillaries do not burst during periods of hypertension, but larger vessels/aneurysm may

Formula for cylinders (Laplace’s Law)

T = Pr

tension increases with an increase in pressure or radius

Why are aneurysm more likely to rupture?

abdominal aorta maintains a MAP along its length, including the aneurysm → greater radius + greater tension = rupture

Formula for spheres (Laplace’s Law)

2T = Pr or T = Pr/2

In spheres, wall tension is what compared to cylinders?

half as much

in Laplace’s law, what does the math show clincally?

greater tension (& risk of rupture) exists with large saccular aneurysms compared to smaller ones

Cardiac Ventricular application of Laplace’s Law

cardiac ventricle (sphere) of increasing size explains inotropic support but eventual failure to contract with increasing wall tension and pressure

• frank-starling curve

Alveolar Application of Laplace’s Law

• lower surface tension = lower pressure required in alveoli to stay open

• surfactant lowers surface tension more in smaller alveoli (greater concentration present) than in larger alveoli

  • → surfactant has the ability to equilibrate surface tension among different-sized alveoli and create stabilized alveolar pressures

What is solubility?

the maximum amount of one substance (solute) that is able to dissolve into another substance (solvent)

What are factors that affect solubility?***

• intermolecular interactions

• temperature

• pressure

When is solubility increased between substances?

when they have similar electron configurations

salt and water have similar polarity

What is a saying to remember for solubility?

like dissolves like

What is temperature needed for in solubility?

to break the bonds of substances that are dissolving

What kind of reaction is temperature usually in solubility?

• endothermic - requires more energy that it produces

• usually when solids dissolve in liquids

What is an endothermic reaction?

consumes instead of produces heat

When there is an increase in temp, what happens to solubility?

it increases

• b/c additional energy/heat promotes more dissolving

what is an exothermic reaction?

energy is released in excess of the energy required to break the bonds of the solute'

• increased temp will decrease solubility

What has little influence on solubility of solids and liquids?

pressure

Temperature in relation to a Gas.

solubility in liquids is inversely r/t to temp

In the solubility of gases, increased temp means …

greater kinetic energy

What does greater kinetic energy of a gas allow?

dissolved gas molecules to escape and prevents further dissolving

What does lower temp do to a gas’ solubility?

slows the kinetic energy of gas molecules allowing them to dissolve into liquids

in gas solubility, as temp increases…

less gas is able to dissolve into a liquid

when the patient is cold, it is harder for patients to wakeup

Pressure in relation to Gas solubility.

gas solubility is directly proportional to pressure (partial pressure)

^^describes Henry’s Law

What is partial pressure?

the percent of a gas in terms of total atmospheric pressure

what is normal atm pressure?

760 mmHg

What is Henry’s law?

at constant temp the amount of gas dissolved in a liquid is directly proportional to the pressure of that gas above the liquid

Simple: more pressure pushes more gas into the liquid

ex: when you open a soda bottle, the pressure release and the gas escapes from the liquid

What is the formula for henry’s law?

p = kc

• p = partial pressure of the solute above the solution

• k = henry’s constant (different for different gases)

• c = concentration of the solute in solution

For Henry’s Law just know …

gas solubility is directly related to partial pressure (think of soda)

How can you figure out the approximate partial pressure of a patient?

multiply the fiO2 by 5

O2 dissolved in blood =

PaO₂ × 0.003

CO₂ dissolved in blood =

PaCO₂ × 0.067

What is entropy?

the universe’s trend to equilibrate all things

What direction is entropy in?

it is unidirectional: movement of energy from high concentration to lower concentration

Why does entropy move?

b/c of a gradient

In entropy, what influences the speed of flow?

the difference in the gradient

Entropy drives the …

universe

What is diffusion?

process of net movement of one type of molecule through space as a result of random motion intended to minimize a concentration gradient

• passive

What is diffusion driven by?

entropy

Why does diffusion occur?

Browninan motion

What is Brownian motion?

the inherit kinetic energy of molecules

What does the kinetic energy of Brownian Motion allow?

molecules to move freely through fluid → mixtures in the fluid tends to be evenly distributed

What does molecular weight determine relative to diffusion?

velocity at which a molecule will distribute

What is temperature’s relationship to kinetic energy?

it is directly proportional to kinetic energy

What does greater velocity correlate to?

faster diffusion

In diffusion, molecules will smaller mass ….

will diffuse faster

Every molecule at a given temp will …, but its …. will be determined by ….

• have the same kinetic energy (regardless of its size)

• velocity

• molecular weight

If a fluid is permeable through a membrane, then ….

diffusion is dependent on 5 factors

What are the 5 factors that diffusion through a membrane is dependent on?

1. concentration gradient

2. tissue area

3. fluid: tissue solubility

4. membrane thickness

5. molecular weight

1, 2, 3 = directly proportional

4, 5 = inversely proportional

What is Graham’s Law?

the rate of effusion (gas diffusion through an orifice) of a gas is directly proportional to the square root of its molecular weight

What is the formula for Graham’s Law?

r = 1/√mw

What is the bottom line of Graham’s Law?

the larger the molecule, the slower it diffuses

What is Fick’s Law?

the rate of transfer is directly proportional to the available surface area and pressure gradient, and inversely proportional to membrane thickness and molecular weight of gas

What is a clinical application of Fick’s Law?

diffusion hypoxia from nitrous oxide

What is osmosis?

movement of water across a semipermeable membrane to balance a concentration gradient

True or false. Semipermeable membranes are permeable to water and solutes.

false, to water only

what is osmotic pressure?

force needed to stop osmosis from occuring

What is oncotic pressure?

pulling force by large proteins in the blood that draws water into the circulatory system

What plasma protein is important for oncotic pressure?

albumin

Oncotic pressure is a type of …

osmotic pressure exerted by plasma proteins

Oncotic pressure opposes …

hydrostatic pressure (pushes water out of capillaries)

What is normal oncotic pressure?

25-30 mmHg

What kind of membrane is vasculature?

semipermeable