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2nd Quarter > Physics Quiz #4 > Flashcards

Physics Quiz #4 Flashcards

1
Q

Both liquids and gases are fluids?

A

True

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2
Q

What are the forces associated with fluids(3)?

A
  • gravity
  • pressure
  • friction
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3
Q

What is friction?

A
  • the resistance to flow from the surface interaction

- it is proportional to viscosity

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4
Q

What is viscosity?

A

The inherent property of a fluid that resists flow

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5
Q

What is the result of pressure forces in a fluid established by differences in pressure from one point to another, which creates a pressure gradient?

A
  • flow

- all flow moves from higher pressure, or resistance to lower

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6
Q

What is Laminar flow?

A

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

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7
Q

Which molecules in laminar flow encounter the least adhesive force of the walls of the tube?

A

molecules in the center of the tube

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8
Q

Molecules in the center of the tube move at a velocity twice that of the mean flow?

A

True

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9
Q

True laminar flow predominates in the smallest airways(terminal bronchioles)?

A

True

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10
Q

What is transitional flow?

A

a mixture of laminar flow along the walls of the tube with turbulent flow in the center

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11
Q

What is turbulent flow?

A

described as chaotic with irregular eddies throughout

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12
Q

Which law is described: In straight circular tubes, the radius will have the most dramatic effect on flow = constancy X Radius to the 4th power(r^4) X pressure gradient

A

Poiseuille’s Law

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13
Q

According to Poiseuille’s law, doubling the radius will result in_____-fold increase in flow; tripling of the radius increases the flow by_____-fold?

A
  • doubling=16 fold

- tripling-81 fold

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14
Q

Resistance is inversely proportional to r^4(the greater the radius, the smaller the resistance).

A

True

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15
Q

When the radius of a tube is tripled, how much will the resistance decrease?

A

81 fold

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16
Q

Resistance is directly proportional to fluid viscosity(the greater the blood viscosity, the greater the resistance).

A

True

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17
Q

Resistance is directly proportional to tube length(the longer the tube, the greater the resistance).

A

True

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18
Q

How are flow and resistance related?

A
  • flow through a tube is inversely proportional to resistance
  • if resistance doubles, flow is halved
  • if resistance is halved, flow is doubled
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19
Q

Whose law is described: When considering flow through a tube, the gradient in hydrostatic pressure(inflow pressure minus outflow pressure) equal flow times resistance.

A

Ohm’s Law

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20
Q

Whose law is described: MAP-CVP = CO x SVR or SVR = (MAP-CVP)/CO x 80

A

Ohm’s Law

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21
Q

What happens to flow and what happens to resistance when the radius of the tube increases? When radius of the tube decreases?

A
  • When the radius of a tube increases, resistance to flow decreases and flow increases
  • When the radius of a tube decreases, resistance to flow increases and flow decreases
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22
Q

Is flow through 16 gauge IV catheter greater or lesser than through a 20 gauge catheter?

A
  • 16 gauge

- the greater the radius, the more flow

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23
Q

What happens to fluid flow if viscosity is increased?

A

flow decreases

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24
Q

Patients with polycythemia have ___ blood flow due to ___ viscosity of blood. Patients with anemia have ___ blood viscosity, hence ___ flows through tissues.

A 
Polycythemia = decreased, greater
Anemia = decreased, greater
25
Q

How will flow be affected when length of a tube increases? If the length of tube is decreased by 50%? If the length of a tube is doubled?

A
  • flow will decrease
  • flow will double
  • flow will be decreased by half
26
Q

If the radius of a tube decreases to 1/3 of its original size, flow will decrease to 1/81 of its original value?

A

true

27
Q

Which of the following will decrease peak inspiratory pressure? 1. change ETT from 8.0 to 6.0 or 2. change ETT from 6.0 to 8.0?

A

changing ETT from a 6.0 to a 8.0 will decrease the PIP, PIP is greater when inflow resistance is higher and vice versa

28
Q

These interventions are a direct manipulation of whose law: To improve flow when delivering a unit of PRBC’s a large-diameter IV catheter is recommend, a pressure bag may be placed on the unit of PRBCs to increase the driving pressure(pressure gradient) and the PRBCs may be diluted with normal saline to lower viscosity.

A

Poiseuille’s Law

29
Q

Which factor will have the most dramatic improvement on flow: increasing the pressure, thinning the liquid(less viscous), shortening the tube, or increasing the diameter of the IV catheter?

A

increasing the diameter of the catheter

30
Q

Identify 3 conditions that can change laminar to turbulent flow during anesthetic administration.

A
  1. Gases changing direction(bend in tube of more than 20 degrees)
  2. increased velocity
  3. rough walled(corrugated) tubes
31
Q

This is used to predict when flow through a cylindrical tube changes from laminar to turbulent.

A

Reynold’s number(Re)

32
Q

Reynold’s number states that resistance to flow increases when flow becomes turbulent.

A

True

33
Q

What is the formula for Reynold’s number(Re)?

A

Re=(fluid velocity x fluid density x tube diameter)/fluid viscosity

34
Q

When Reynold’s number exceeds 1500-2000, flow changes from laminar to turbulent

A

true

35
Q

When flow is turbulent, density(p), not viscosity(n), determines flow.

A

true

36
Q

Identify the Reynold’s number at which laminar flow changes to turbulent flow.

A

> 2000, flow changes from laminar to turbulent

37
Q

When density is large, Re is ___?

A

Large(turbulent)

38
Q

When viscosity is large, Re is ___?

A

small(laminar)

39
Q

Viscosity is a determinant of gas flow when flow is laminar?

A

True
-flow is inversely proportional to viscosity(the greater the viscosity, the lower the flow) when flow is laminar(non-turbulent).

40
Q

What property of a gas determines gas flow rate through a variable orifice flow meter at low flow rates?

A
  • viscosity

- flow through a variable orifice flow meter is laminar when flow is low, so flow is inversely proportional to viscosity

41
Q

What property of gas determines gas flow rate through a variable orifice flow meter a high flow rates?

A
  • Density
  • With high flows, flow through a variable orifice flow meter is turbulent and flow rate is inversely proportional to gas density.
42
Q

Delivery of which mixture to status asthmatics patients who are refractory to standard treatments, will help in reestablishing laminar flow through airway: delivery of He/O2 mixtures, or delivery of N2O/O2 mixtures?

A

Helium, which has a significantly lower density than nitrogen, improves flow by restoring laminar flow through the significantly narrowed airways of a severe asthma attach.

43
Q

Describe Orifice Flow.

A
  • a type of turbulent flow
  • occurs at severe constrictions, such as a nearly closed larynx, trachea, or kinked ETT
  • can occur when the diameter of tube is greater than the tube length.
44
Q

What is Bernoulli’s Principle?

A
  • describes the effect of fluids(liquids and gases) flow through a tube containing a constriction
  • as flow passes through the narrowing in a tube, the velocity of that flow increases
45
Q

What is the Venturi effect?

A
  • jet effect
  • as with a funnel, the velocity of the fluid increases as the cross sectional area decreases, with the static pressure correspondingly decreasing
  • by placing the orifice at the narrowed region of flow, air is allowed to be entrained and to enter the flow
  • air may be entrained into a flow of liquid, or a liquid may be entrained into a flow of gas
46
Q

Venturi extended whose work? What observations did Venturi make?

A
  • Venturi extended Bernoulli’s work on the relationship between the velocity of flow of a fluid and the lateral pressure exerted on the wall of a tube.
  • the lateral pressure exerted by a fluid(gas or liquid) going through a tube of varying diameter is lowest at the narrowest part, where velocity is greatest
47
Q

What is LaPlace’s Law?

A

-describes the relationship of wall tension(T) to pressure(P) and radius(r) in cylinders(blood vessels, left cardiac ventricle) and spheres(alveoli with and without surfactant)

48
Q

Define Tension

A
  • the internal force generated by a structure
  • a linear force
  • a force directed along a straight line(formulas to calculate tension vary between cylinders and spheres)
49
Q

What is LaPlace’s law and cylindrical calculation for Tension?

A

As a cylinder expands(the radius increases), the tension(force) in the wall of the structure increases
Tension(T) = Pressure(P) x radius(r)

50
Q

Is an aortic aneurysm more likely to rupture than a normal segment of aorta?

A

yes, because the radius is larger, it increases the tension in the wall to the “breaking point”

51
Q

What vessel can withstand a pressure of 100 mmHg better; a capillary or a vein?

A
  • a capillary
  • it has a tiny radius compared to a vein
  • the tension in the wall of the capillary is extraordinarily smaller than that of a vein
52
Q

The law of LaPlace states that the tension in the left ventricular wall of the heart is increased when filling is increased?

A
  • True
  • the greater the filling, the greater the tension
  • since the left ventricular wall has a substantial thickness, the law of LaPlace is modified to account for wall thickness(h)
53
Q

What is LaPlace’s calculation for spherically-shaped structures, such as alveoli?

A

-in spheres, wall tension is increased twice as much, with increasing radius compared to cylinders
P x r = 2T or T= (P x r)/2

54
Q

When do you need more pressure to blow up a ballon?

A

when the ballon is small

55
Q

For alveoli that are deficient of normal surfactant(as well as for a plastic ballon), wall tension is content and independent of radius?

A
  • true
  • because tension in the wall is independent of size, the pressure inside the surfactant-deficient alveoli will change with size
56
Q

Pressure is greater in the larger alveoli than the smaller alveoli?

A
  • false

- according to LaPlace, if two alveoli have the same surface tension, the smaller sphere will have higher pressure

57
Q

Smaller alveoli empty into larger alveoli causing atelectasis in patients with ARDS and premature neonates who are deficient of surfactant?

A

True

58
Q

For alveoli with surfactant(the normal situation), tension increases with increases in radius?

A
  • true
  • because alveolar will tension increases in proportion to increases in radius, the pressure within the alveolus does not change
59
Q

What principle of physics explains the operation of the high frequency jet ventilator?

A

the Venturi effect

2nd Quarter (27 decks)

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