Flashcards in Physics Quiz #4 Deck (59):

1

## Both liquids and gases are fluids?

### True

2

## What are the forces associated with fluids(3)?

###
-gravity

-pressure

-friction

3

## What is friction?

###
-the resistance to flow from the surface interaction

-it is proportional to viscosity

4

## What is viscosity?

### The inherent property of a fluid that resists flow

5

## 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?

###
-flow

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

6

## What is Laminar flow?

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

7

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

### molecules in the center of the tube

8

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

### True

9

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

### True

10

## What is transitional flow?

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

11

## What is turbulent flow?

### described as chaotic with irregular eddies throughout

12

## 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

### Poiseuille's Law

13

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

###
-doubling=16 fold

-tripling-81 fold

14

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

###
True

15

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

### 81 fold

16

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

### True

17

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

### True

18

## How are flow and resistance related?

###
-flow through a tube is inversely proportional to resistance

-if resistance doubles, flow is halved

-if resistance is halved, flow is doubled

19

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

### Ohm's Law

20

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

### Ohm's Law

21

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

###
-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

22

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

###
-16 gauge

-the greater the radius, the more flow

23

## What happens to fluid flow if viscosity is increased?

### flow decreases

24

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

###
Polycythemia = decreased, greater

Anemia = decreased, greater

25

## 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?

###
-flow will decrease

-flow will double

-flow will be decreased by half

26

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

### true

27

## 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?

### 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

## 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.

### Poiseuille's Law

29

## 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?

### increasing the diameter of the catheter

30

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

###
1. Gases changing direction(bend in tube of more than 20 degrees)

2. increased velocity

3. rough walled(corrugated) tubes

31

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

### Reynold's number(Re)

32

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

### True

33

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

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

34

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

### true

35

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

### true

36

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

### > 2000, flow changes from laminar to turbulent

37

## When density is large, Re is ___?

### Large(turbulent)

38

## When viscosity is large, Re is ___?

### small(laminar)

39

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

###
True

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

40

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

###
-viscosity

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

41

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

###
-Density

-With high flows, flow through a variable orifice flow meter is turbulent and flow rate is inversely proportional to gas density.

42

## 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?

### 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

## Describe Orifice Flow.

###
- 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

## What is Bernoulli's Principle?

###
-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

## What is the Venturi effect?

###
-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

## Venturi extended whose work? What observations did Venturi make?

###
-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

## What is LaPlace's Law?

### -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

## Define Tension

###
-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

## What is LaPlace's law and cylindrical calculation for Tension?

###
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

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

### yes, because the radius is larger, it increases the tension in the wall to the "breaking point"

51

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

###
-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

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

###
-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

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

###
-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

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

### when the ballon is small

55

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

###
-true

-because tension in the wall is independent of size, the pressure inside the surfactant-deficient alveoli will change with size

56

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

###
-false

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

57

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

### True

58

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

###
-true

-because alveolar will tension increases in proportion to increases in radius, the pressure within the alveolus does not change

59