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N927 Chemistry & Physics of Anesthesia > Lecture 7A - Fluids & Flow > Flashcards

Lecture 7A - Fluids & Flow Flashcards

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1
Q

energy

A
  • capacity to do work
  • the internal energy of a system is the sum of all the potential and kinetic energy in the particles within the system
  • the internal energy is a quantity results from the state of the particles within a system
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2
Q

work

A

-work = force X distance
-measure the amount of change a force produces when it acts on a body
(ForkeD)

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3
Q

forms of energy

A
  • light
  • water
  • magnetic
  • heat
  • chemical
  • electrical
  • sound
  • wind
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4
Q

energy building blocks

A

potential energy + kinetic energy

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5
Q

kinetic energy

A
  • energy of movement
  • inherent energy in the motion of a body
  • associates mass and motion (velocity)
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6
Q

velocity

A

-distance traveled per unit time

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7
Q

KE formula

A

M X V(squared) X 0.5

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8
Q

potential energy

A

-energy stored for later use (positional use)
-stored capacity of a body or a system to do work by virtue of its configuration or position
-amount of work an object can do by returning to its original position
-stretched elastic band:
- inflated lung, filled heart, electrochemical
gradient across cell membrane, compressed CW

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9
Q

potential energy formula

A

mass X gravity X height = MGH

mnemonic: when you drive through a pot hole you go, “MGH!!!”

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10
Q

KE formula

A

[mass X velocity (squared) ] / 2

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11
Q

thermodynamics

A
  • study of energy
  • how it is converted from one form to another and back again
  • how it flows into and out of the system
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12
Q

Zeroth Law of Thermodynamics

A

-no heat will flow between 2 objects when they are placed in contact with one another if they are in thermal equilibrium (both have the same temperature)
(0th Law: 0 temp difference, 0 energy movement)

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13
Q

First Law of Thermodynamics

A

-law of conversation of energy
- energy cannot be created or destroyed
- energy can be transformed from one kind of energy
into another kind of energy
-the change in the internal energy of system is equal to sum of the heat processes that cause energy to flow into or out of a system
(1st law: everything has to equal 1 whole so law of conservation of energy)

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14
Q

Second Law of Thermodynamics

A
  • 2 objects with 2 different temps and heat will flow from higher to lower temps
    -heat flows from a body of higher temperature to a body of lower temperature when the 2 bodies are in contact with one another
    (2nd Law: 2 objects, 2 temps)
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15
Q

Entropy

A
  • greater the entropy, the less available the energy for work
  • entropy indicates the degree to which a given quantity of thermal energy is available for doing useful work
    (mnemonic: when I go somewhere tropical, I can’t do work)
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16
Q

Third Law of Thermodynamics

A
  • the temperature of an object can not be lowered to absolute zero
  • zero degree Kelvin (0 degree K)
  • no movement of H2O molecules
    (mnemonic: make the hand # for 3 with pointer and thumb together –> makes a zero for 0 degrees K, absolute 0, cannot get to absolute 0)
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17
Q

what 2 things make a fluid?

A
  • liquid

- gas

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18
Q

Poiseuille Law

A
  • fluid flows through a tube

(mnemonic: poise (like the tampon brand) = tube

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19
Q

Graham Law

A
  • fluid flows through an orifice

mnemonic: graham crackers and oreos

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20
Q

Flow Formula

A

Flow = pressure gradient/resistance

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21
Q

Fluids have what two things

A

KE + PE

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22
Q

CRNA Application of Fluid Flow

A
  • flowmeter
  • heliox (diameter)
  • IV Fluids (gauge of cannulas)
  • ventilation (diameter of airway tubes)
  • anesthesia vaporizer
  • hemodynamic regulation
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23
Q

Pressure Formula

A

Pressure = Force/Area

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24
Q

What is force - 3 P’s

A
  • force can push, pull, pivot a fluid (liquid or gas)
  • force is energy
  • energy is the capability to do work
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25
Q

Pressure Definition

A
  • a force exerted by atoms and molecules
  • molecules have motion
  • molecules have mass
  • gravity gives molecules weight
  • pressure = force/area –> force applied to an object over its surface area
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26
Q

Is Pressure evenly distributed?

A

YES! Pressure will be evenly distributed.

  • as the molecule bumps into the wall and each other, the force is spread evenly over the area.
  • remember: Pressure = force/area
  • so you can put your pressure gauge anywhere within the pressurized area and it will give you the same readings throughout
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27
Q

what is force?

A

force is the 3 P’s - push, pull, pivot of mass

aka speed up [push], slow down [pull], change direction [pivot]

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28
Q

electromagnetic force

A

a force that has the ability to attract and repel charges and thereby make them speed up, slow down, or change direction

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29
Q

gravitational force

A

the natural phenomenon of attraction between two physical objects

  • gravity is the force that attracts objects of mass towards each other
  • G-force is what causes things to accelerate
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30
Q

what is G-force?

A

G-force is the amount of acceleration caused by gravity

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31
Q

force and velocity

A

if an object has force acting on it (aka speed up or slow down) then its velocity is changing
-velocity is distance travelled over unit time

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32
Q

What is a change in velocity called?

A

acceleration

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33
Q

Force Equation

A

Force = Mass X Acceleration

  • so increase mass will increase force
  • increase acceleration will increase force
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34
Q

force definition

A

force can change or tends to change the state of rest or motion of an object
-force is the push or pull on an object

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35
Q

What does the push of pull of force do to an object?

A
  • start it moving if it is still (push)
  • stop its movement if it is moving (pull)
  • speed it up (Push)
  • slow it down (pull)
  • change its direction (pivot)
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36
Q

force and velocity relationship

A

a force will change the velocity of an object

- aka a force will change the distance travelled per unit time of an object

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37
Q

Force Formula

A

Force = Mass X Acceleration

mnemonic: FMLA

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38
Q

Is force a vector?

A

YES

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39
Q

what does force as a vector mean?

A

think of force as a vector which means it has direction and magnitude
(mnemonic : Force Vector to have direction and magnify the tude)

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40
Q

What is force measured in?

A 
Newtons (kg X (meters/second2)) 
Fig Newtons
Force = Mass X Acceleration 
so mass = kg
acceleration = meters/second (squared)
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41
Q

force and velocity relationship

A
  • a force is an influence that causes a change in the motion (velocity) of an object that has mass
  • a force can accelerate an object that has mass (push)
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42
Q

formula for work

A

work = force X distance
so therefore when force is applied to an object, work can be done
- the magnitude of the work is calculated as the distance over which the mass (object) was accelerated (velocity changed - distance travelled per unit time)

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43
Q

work is the exertion of what?

A

force to produce movement

formula for work is force X distance

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44
Q

work is….

A

force X distance
so force applied over a certain distance is work
(ForkeD)

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45
Q

formula for force

A

force = mass X acceleration

FMLA

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46
Q

work =

A

force X distance

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47
Q

work =

A

mass X acceleration X distance

(force) X distance

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48
Q

work =

A 
mass X acceleration X distance
kg X meters/second squared X meters
(kg X meters/second squared = 1 Newton)
so.....
work = Newton Meters
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49
Q

finalized units of work

A

Newton X meters

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50
Q

what does 1 Newton X Meters =

A

joule

Nemonic: Joule met Newton

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51
Q

What is a Newton?

A

mass X meters/ second squared

kg X 1 meter/ second squared

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52
Q

what is the force of gravity?

A

Force of Gravity = 9.81 meters/second squared
(Nemonic: space launch countdown 9, 8, 7 (but think 1)

so 9.81 meters/second squared

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53
Q

What is the force of gravity on a human?

A

take human KG weight X 9.81 meters/second squared

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54
Q

What is a dyne?

A

1 gm X 1cm/sec squared
(Dyne on grams and cents newtons)
because it is the same a Newton but with grams and centimeters in place of kg and meters

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55
Q

energy is the currency of what?

A

energy is the currency of force

force field energy

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56
Q

What does applying force to an object do?

A

to apply force to an object, some amount of energy must be transferred to the object
- thermal, potential, and kinetic are examples of types of energy that are transferred to an object

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57
Q

how is work accomplished?

A

transfer of energy to an object over a certain distance is how work is accomplished
(force field energy) –> energy is the currency of force, work = force X distance. so transfer of energy to an object over a certain distance is how work is accomplished

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58
Q

Potential energy formula

A

M X G X H

think: MGH when you drive over a pothole

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59
Q

M X G X H with different units applied is…

A

Newton X M
mass = kg
G = kg X meters/second2
so M X G X H = Newton X Meter

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60
Q

How are KE and PE measured? (units)

A

Joules

Memory trick: joulE went to work at the Energy plant

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61
Q

force changes what?

A

velocity of an object aka changes the acceleration of an object

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62
Q

formula for work

A

work = force X distance

ForkeD

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63
Q

energy is

A

the capability to do work

- energy is expended when work is done

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64
Q

work and energy are measured in?

A

JOULES

- memory trick: joulE went to work at the Energy plant

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65
Q

What is power?

A

power is the capacity to do work and is quantified as the amount of work done per unit time
- power = work/unit time
(Memory trick: power through overtime work…so power = work over time aka power = work/time)

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66
Q

What is power related to?

A

power is related to force, work, and energy
How? power = work/time
force = work X distance
energy is the currency of work

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67
Q

Formula for power?

A

power through overtime work….
work/time = joules/second

(JoulE goes to work at the Energy plant)

power = work/time = joules/second = watts

Think: WaPOW (like a hit) so power is in watts

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68
Q

formula for pressure

A

pressure = force/area

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69
Q

what is pressure?

A

force extended by atoms and molecules

  • generated by kinetic energy
  • have molecular weight and motion
  • gravity and energy is imparted to the particles
  • is the force applied to an object over its surface area
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70
Q

what direction is pressure applied?

A

in a direction perpendicular to the surface of the object

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71
Q

what type of quantity is pressure?

A

scalar quantity

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72
Q

what does an increase in density do to the pressure?

A

increased density = increased pressure

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73
Q

what does a reduction in density do to the pressure?

A

decreased density = decreased pressure

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74
Q

what is the formula for flow?

A 
Q = delta P/R
flow = pressure gradient/resistance

so rearranged could be:

  • delta P = F X R
  • R = delta P/F
75
Q

what are the two types of flow?

A

Turbulent and Laminar

76
Q

what is laminar flow?

A

Laminar Flow is molecules move in sheets from IMF

think: laminated papers in sheets

77
Q

what is turbulent flow?

A

Turbulent flow is molecules moving with disrupted sheets

78
Q

Does laminar slow have more or less resistance?

A

Laminar flow has less resistance to airflow

Again think laminated paper is smooth feeling

79
Q

Does turbulent flow have more or less resistance?

A

Turbulent flow has more resistance to airflow

80
Q

What creates the resistance in laminar and turbulent flow?

A

adhesion forces with the fluids attraction to the wall which creates drag on the molecules in sheets against the wall. –> the sheets against the wall have IMF with the lower sheet (cohesive forces) so then they drag on them, and that sheet has IMF with the sheet below it, etc.

81
Q

what area of the laminar flow will experience the least amount of resistance?

A

the inner most because will experience the least amount of drag from the adhesion forces of the molecules attraction to the wall

82
Q

What does increased viscosity do to the flow of a fluid?

A

increased viscosity = decreased flow

83
Q

what does reduced viscosity do to the flow of a fluid?

A

reduced viscosity = increased flow

84
Q

how does turbulent flow affect resistance?

A

turbulent flow leads to increased resistance to the gas flowing through the tube

85
Q

what is the physiological impact of turbulent flow?

A

turbulent flow = increased resistance = increased pressure to move air = increased WOB, increased cardiac workload
AKA turbulent flow causes increased work demand

86
Q

Definition of Resistance

A

resistance is a passive force exerted in opposition to another active force

87
Q

Is resistance an active or passive force?

A

resistance is a passive force.

it acts on the active forces.

88
Q

What is the practical use of resistance?

A

resistance is the decline in pressure which results when a fluid (gas of liquid) flows through a tube

89
Q

what declines due to resistance?

A

pressure declines due to resistance

90
Q

what two forces cause resistance?

A

COHESION & ADHESION
adhesion = attraction to the wall
cohesion = attraction to like molecules in the fluid

91
Q

resistance causes what?

A

friction

92
Q

what is viscosity?

A

viscosity is a measure of a fluids internal resistance (cohesive force) to flow

93
Q

does viscosity increase or decrease with increasing IMF?

A

viscosity increases with increasing IMF

94
Q

does viscosity increase or decrease with decreasing IMF?

A

viscosity decreases with decreasing IMF

95
Q

does viscosity measure adhesive or cohesive forces?

A

viscosity measures cohesive forces

96
Q

how can you decrease the viscosity of a fluid?

A

to decrease the viscosity of a fluid, add head to increase the KE of the molecules. Increased KE of molecules will increase the movement of the molecules and therefore create a higher likelihood to overcome the IMF

97
Q

Poiseueille’s Law refers to fluids flowing through a…

A

tube

98
Q

Poiseueille’s Law describes laminar or turbulent flow?

A

Poiseueille’s Law describes laminar flow.

Poise (like the tampon brand) is a tube. and periods are lame. so poiseueille’s law is about flow through a tube with laminar flow.
periods are lame and poise is a tampon for tubular flow.

99
Q

Flow is directly or inversely proportional to radius?

A

flow is directly proportional to radius.
increase radius = increased flow
decreased radius = decreased flow

100
Q

Flow is directly or inversely proportional to pressure gradient?

A

Flow is directly proportional to pressure gradient.
Increased pressure gradient = increased flow.
Decrease pressure gradient = decreased flow.

101
Q

Flow is directly or inversely proportional to viscosity?

A

Flow is inversely proportional to viscosity.
Increased viscosity = decreased flow.
Decreased viscosity = increased flow.

102
Q

Flow is directly or inversely proportional to length?

A

Flow is inversely proportional to length.
Increased length = decreased flow (because of resistance forces along the length of the tube)
decreased length = increased flow

103
Q

What is longer in a tube? What is shorter in a tube?

A

A tube has a longer length and a shorter diameter.

Length > Diameter

104
Q

what is the formula for flow?

A 
Q = delta P/R
...rearranged
Q X R = delta P
....rearranged
R = delta P/ Q
105
Q

Poiseueille’s Law Formula

A

F = pi X radius (4th power) X delta Pressure/ (8 X viscosity) X length)

106
Q

does a lower needle gauge increase or decrease flow?

A

increase flow….increased flow through 18 g then 22 g

107
Q

does a shorter needle length increase or decrease flow?

A

increase flow with shorter needle length (aka less resistance forces…resistance is passive force (adhesion) acting on active flow forces (cohesion))

108
Q

does increased hydrostatic pressure increase or decrease flow?

A

increased hydrostatic pressure increases flow…

increased pressure = increased flow

109
Q

does a polycythemic patient have increased or decreased flow?

A

polycythemia means increased viscosity. increased viscosity = decreased flow.

110
Q

How could you improve flow in a patient with polycythemia?

A

hydrate and warm the sickle cell disease patient…

the increased temperature will increase KE and increased movement of molecules to break IMF and therefore increase flow

111
Q

does an anemic patient have increased or decreased blood flow?

A

An anemic patient has increased blood flow because has decreased viscosity.

112
Q

What is a tube?

A

a tube is a passage where length > diameter

113
Q

what law applies to tubes?

A

Poiseulles Law

114
Q

what flow is present in tube/Posieulle’s Law?

A

Laminar Flow

Periods are Lame

115
Q

Poiseuille’s Law relates to what factors?

A

F= pi X radius(to the fourth) X delta P/ (8 X viscosity) X length

  • diameter
  • pressure differential
  • length
  • viscosity
116
Q

What law related to orifices?

A

Graham’s Law relates to orifices

Graham crackers and oreos

117
Q

what is an orifice?

A

an orifice is an opening through which a fluid may pass whose diameter is greater than its length
diameter > length

118
Q

in an orifice which is bigger, the diameter or the length?

A

Diameter > length (think oreo is a circle)

119
Q

Graham’s Law relates flow through an orifice to:

A

Graham’s law relates flow through an orifice to density.

We keep graham crackers and oreos in the den.

120
Q

What is the formula for density?

A

Density = Molecular weight of gas

121
Q

what is the formula for flow rate?

A

Flow rate = 1/ sq. root of MW

- the bigger the molecular weight, the slower the flow

122
Q

What causes turbulent flow?

A

turbulent flow is a disruption of the molecular sheets. This disruption occurs at the branches and bend of blood vessels/airways

123
Q

What are pathological things that cause turbulent flow in the body?

A

Mucus in airway, plaque in blood vessel = introduce turbulent flow which injures endothelium and increases entropy.

124
Q

Does turbulent flow increase or decrease resistance?

A

Turbulent flow INCREASES resistance

125
Q

Is turbulent flow directly or indirectly proportional to resistance?

A

turbulent flow is directly proportional to resistance.

126
Q

What law applies to tubular flow?

A

Poiselle’s Law

127
Q

Poiselle’s Law applies to what type of flow?

A

Laminar flow (periods are lame)

128
Q

What is a determinant of laminar flow?

A

Viscosity is the determinant of laminar flow.

blood is thick. periods are lame

129
Q

What is the major factor of laminar flow?

A

Viscosity is the major factor of laminar flow.

blood is thick. periods are lame

130
Q

What is the major determinant of turbulent flow?

A

Density is the major determinant of turbulent flow.

-graham crackers and oreos in the den with a tub of ice cream.

131
Q

Is flow directly or inversely proportional to density?

A

flow is inversely proportional to density.
as density increases, flow decreases.
as density decreases, flow increases.

132
Q

What is the nemonic for the entire turbulent flow cascade of definitions?

A

Graham Crackers and oreos in the den with a tub of ice cream.

  • Graham’s law
  • Orifice
  • density
  • turbulent flow
133
Q

What is the nemonic for the entire laminar flow cascade of definitions?

A

Poise (like the tampon brand), tampon is a tube shape, periods are lame, blood is thick.

  • Poiseuelle’s law
  • tubes
  • laminar flow
  • viscosity
134
Q

What does Reynold’s law state?

A

increased diameter, increases turbulence.
Thus, laminar flow (through a tube, Poiselles law, laminar flow, viscosity) becomes turbulent flow (through an orifice…Graham’s law, orifice, density, turbulent flow).

135
Q

Is turbulent flow directly or inversely proportional to density?

A

Turbulent flow inversely proportional to density.
decreased density = increased turbulent flow
increased density = decreased turbulent flow.

136
Q

Is turbulent flow directly or inversely proportional to MW?

A

MW = density so…
turbulent flow is inversely proportional to MW.
increased MW = decreased turbulent flow.
decreased MW = increased turbulent flow.

137
Q

Is laminar flow through a tube directly or inversely dependent on viscosity?

A

Laminar flow is inversely proportional to viscosity.
increased viscosity = decreased laminar flow
decreased viscosity = increased laminar flow
periods are lame, blood is thick.

138
Q

What does reynold’s number predict?

A

Reynold’s number predicts when flow through a tube changes from laminar to turbulent

139
Q

What does Reynold’s number predict?

A

When flow through a tube will change from laminar to turbulent

140
Q

Is Reynold’s number about tubes or orifices?

A

Reynold’s number applies to when the tube flow will change from laminar to turbulent.

141
Q

Reynolds number is directly or inversely proportional to velocity?

A

Reynold’s number would be directly proportional to velocity.

increased velocity = increased Reynold’s number

142
Q

Reynolds number is directly or inversely proportional to tube diameter?

A

Reynold’s number is directly proportional to tube diameter.
Reynold’s number is all about if the diameter of the tube increases enough then the flow will transition from laminar to turbulent.

143
Q

Reynold’s number is directly or inversely proportional to fluid density?

A

Reynold’s number is directly proportional to density.
An increase in density = increase reynold’s number
a decrease in density = decreased Reynold’s number

144
Q

Reynold’s number is directly or inversely proportional to viscosity?

A

Reynold’s number is inversely proportional to viscosity.

145
Q

At what Reynold’s number does flow change from laminar to turbulent?

A

At >2000 flow changes from laminar to turbulent for Reynold’s number.

146
Q

if the velocity of the fluid is high, the turbulent is high or low?

A

if the velocity of the fluid is high, the turbulence is high

147
Q

if the tube narrows or have kinks or angles that introduces what?

A

narrowing, kinks, or angles introduces turbulent flow.

148
Q

which will increase turbulence a smooth or a rough wall?

A

A rough wall will increase turbulence.

149
Q

with a tube or an orifice have more turbulent flow?

A

An orifice will have more turbulent flow (Think of the backbone of Reynold’s number…when a tube becomes more like an orifice then you have turbulent flow)

150
Q

What happens to resistance when turbulence increases?

Does resistance go up or down?

A

when turbulence increases, resistance increases.

151
Q

what determines the turbulence of the gas flow?

A

Density determines the turbulence of the gas flow.

Graham Crackers and oreos in the den with ice cream.

152
Q

when flow increases, density increases or decreases?

A

when flow increases, density decreases.

153
Q

What is a clinical application of density and its application to anesthesia?

A

Heliox with oxygen gas mixture.
Helium is less dense than nitrogen. (helium is smaller than nitrogen)
Flow rate is inverse to density.
So as density decreases, flow increases.

154
Q

What is critical flow rate?

A

Critical Flow Rate is the velocity at which a liquid or gas converts from laminar to turbulent flow

155
Q

What happens to turbulence when you increase velocity?

A

When velocity increases, the likelihood of turbulent flow increases. Critical Flow Rate is the velocity at which a liquid or a gas converts from laminar to turbulent flow.

156
Q

When motion increases what force increases?

A

Kinetic Energy increases with increased motion because the energy of motion is increasing.

157
Q

Due to the conversation of energy where energy can be neither created nor destroyed (1st law of thermodynamics), if kinetic energy increases (and all the particles are in motion in a tube) then what will decrease?

A

Laminar Flow Concept.

  • the radius decreases then to maintain the same flow, the velocity must increase. If the velocity increases then the motion increases. If the motion increases then the KE increases. According to the 1st law of thermodynamics, energy can be neither created nor destroyed, so therefore the pressure energy must decrease.
  • So KE increases due to increased velocity to maintain same flow, pressure energy decreases to maintain same total energy.
158
Q

If velocity keeps increasing, the what flow rate will be reached and what will happen at this flow rate?

A

If velocity continues to increase then you could reach critical flow rate, and then laminar flow could turn into turbulent flow?

159
Q

What normally causes turbulent flow?

A

Bends, curves, branches, and corners cause turbulent flow.

160
Q

What is Bernoulli’s Theorem?

A

Bernoulli’s Theorem states in a tube of varying diameter, a decrease in diameter results in an increase in velocity.

  • aka a more narrow tube will have an increased velocity to reach the same flow.
  • therefore the energy of motion increases (KE), and the pressure energy decreases (pressure energy)
161
Q

In a tube, when you decrease the pressure energy what happens to fluids that are adjacent to the main tube?

A

If the diameter narrows and the KE increases and the pressure energy decreases then that creates a vacuum to suck up fluid from the adjacent tubes.

162
Q

What is the Venturi effect?

A

Bernoulli’s Theorem

  • when the tube narrows, in order to maintain the same flow, the velocity (KE) increases which means the pressure energy decreases. When the pressure energy decreases it creates a vacuum. This pressure vacuum sucks other fluids into the main tube and allows them to mix.
  • generation of a sub-atmospheric pressure after the constriction allows a second gas to be drawn inward and mixed with the first gas
163
Q

How do venturi masks work?

A

Venturi masks work using Bernoulli’s theorem.
When the tube narrows, in order to keep the same flow, the KE (velocity) increases and the pressure energy decreases because the particles cannot interact with the wall as much. Therefore, the decrease in pressure creates a vacuum. The vacuum of pressure suctions adjacent fluids into the main tube and allows for mixing.
AKA the tube narrows and the lower pressure energy in the tube then the more suction of gas in from room air through an adjacent orifice.

164
Q

What theory is the pressure energy theory?

A

Pascal’s Theory is the pressure energy theory.

165
Q

How do you dilute oxygen with the venturi mask?

A

You choose the associated piece that has a specific orifice opening, this allows a certain amount of air to be suctioned into the tube.

166
Q

What are the relationships between the venturi mask and the pressure, suction, and gas flow?

A

For the Venturi effect, using Bernoulli’s principle, the more narrowing, the lesser the pressure energy, the greater the suction, the more the adjacent gas flow (RA) through the orifice.

167
Q

What in the venturi determines the amount of RA that will be suction into the tube?

A

The adapters narrowing of the tube determines how much or how little RA is suctioned into the tube through its adjacent orifice.

168
Q

What is the starling resistor as an airway model?

A

The starling resistor device consists of an elastic (collapsible) tube mounted inside a chamber filled with air. The pressure inside the chamber was used to control the degree of narrowing of the tube (providing a variable resistance to flow).

  • you put a collapsible tube inside a chamber and you can adjust the pressure in there.
  • a certain pressure leads to a certain narrowing so you are adjusting the diameter in the tube
  • if you’re adjusting the diameter then you are adjusting the resistance which means you’re adjusting the flow
  • you can choose the pressure in the chamber that will narrow the tube (like airways narrowing) that will increase the resistance and that will reduce the flow.
  • if you reduce the pressure, (& increase the diameter of the tube) that would increase the flow through the tube.
169
Q

In a venturi mask, what increases and what decreases with the narrowing of the tube?

A

As the tube narrows, the kinetic energy increases and the pressure energy decreases. This creates a vacuum of pressure and allows the fluid to be sucked into the tube.

170
Q

What is a variable orifice flowmeter?

A

A variable orifice flowmeter is a tapered tube with a variable surface area

  • it is narrow at the bottom and wider at the top.
  • called a thorpe tube
  • the bobber in the tube will move up and down as you increase or decrease the diameter of the tube –> therefore you can increase the flow without increasing the pressure if you increase the diameter of the tube.
171
Q

What happens to resistance when you increase the diameter? How would this affect flow?

A

Then you increase the diameter, you decrease resistance. This would increase flow. This is the principle behind the variable orifice flowmeter.

172
Q

Explain the physics of the variable orifice flowmeter?

A

The flowmeter tube widens from inlet to outlet. The float/bobber indicates the flowrate. As the flow rate increases, the pressure would normally increase with a stable diameter tube. However, it the pressure does not increase because the diameter of the tube also gets larger which keep the pressure stable.

173
Q

Explain flow, resistance, and pressure as they relate to the variable orifice flowmeter.

A

A resistance decreases, flow increases and the pressure stays the same because the diameter of the tube also increases.

174
Q

As you increase the flow rates what type of flow (laminar or turbulent) are you more likely to have?

A

As you increase the flow rates, you are more likely to have turbulent flow. (the bobber will start shaking in the variable orifice device)

175
Q

What remains stable in the variable orifice flowmeter?

A

the pressure remains stable in the variable orifice flowmeter because the diameter of the tube increases as the flow increases and therefore you have stable pressure.
AKA the levels of the pressure transducers at the side of the tube would stay level with each other up and down the tube

176
Q

what shape is the variable orifice flowmeter?

A

funnel shaped

177
Q

what is the formula for pressure

A

Pressure = force/area

178
Q

Describe how pressure relates to wider and more narrow syringes?

A

When the same amount of force is applied to both the narrow and wide syringe the area is different. If the surface area is smaller (aka the more narrow syringe) then the pressure for the given force will be bigger. If the syringe is wider (aka more surface area) than the pressure for the given force will be smaller.

179
Q

What physical parts make up a pressure release valve?

A

For a pressure release valve, the valve is fastened to a tube. The spring exerts a particular force on the disc.
The disc has a particular surface area.
Therefore you have a particular force/particular surface area = particular pressure.

180
Q

What happens in a pressure release valve if the pressure in the tube exceeds the pressure of the spring valve?

A

If the pressure in the tube exceeds the valve pressure, then the valve is pushed up revealing vents through which pressure can be dissipated.

181
Q

If the pressure in a pressure release valve is greater than the tube, then what will happen?

A

If the pressure is greater in the pressure release valve than the tube, then nothing will happen. The tube will not vent because the pressure within the tube does not exceed the pressure of the pressure relief valve.

182
Q

If the pressure in a pressure release valve is less than the tube pressure?

A

If the tube pressure is greater than the spring valve pressure, then the spring valve would be pushed up and the vents would be revealed. Pressure would vent from the tube out through the pressure relief valve until the pressures reach equilibrium.

183
Q

What is the physics behind the pressure relief valve?

A

The physics behind the pressure relief valve is….the high pressure entering the valve pushes the diaphragm upward against the downward force produced by the spring. Pressure energy is used to do work moving the diaphragm therefore, not transmitted to gas outlet.

N927 Chemistry & Physics of Anesthesia (3 decks)

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