Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BLOCK B - RESPIRATION > Lung Dynamics > Flashcards

Lung Dynamics Flashcards

1
Q

What are lung dynamics?

A

Mechanical behavior of lungs during periods of airflow (lung volumes are changing over time)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Lung dynamics are governed by…

A

physical characteristics of the airways, through which airflow occurs, and the lung parenchyma.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the lung parenchyma?

A

It is the functional tissue of the lungs involved in gas exchange. It is mainly composed of the walls of the alveoli.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain laminar vs turbulent flow

A

Laminar flow occurs when the flow stream lines are parallel to the sides of the tube. Gas is more localized in the middle of the tube.

Turbulent flow occurs when the stream lines become chaotic. The mean forward velocity of the gas is the same at any point in the flow, whether in the centre of the tube or near the walls.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What influences the nature of airflow as gas moves from the mouth to the alveoli and back?

A

The size of the airways determines in large part the nature of flow (laminar vs turbulent, which changes as gas moves from the mouth to the alveoli and back.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where is flow more turbulent? Where is flow more laminar?

A

Turbulent: larger airways
Laminar: smaller airways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is required for a gas to move across a tube?

A

A pressure difference (ie. driving pressure called delta P) between the two ends of a tube.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is another name for laminar flow?

A

Poiseuille flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

With laminar flow, the flow rate (V dot) is directly proportional to…

A

the driving pressure (ΔP)

ΔP∝K1*(Vdot)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

With turbulent flow, the driving pressure needed to maintain a given flow varies with…

A

the square of the flow rate (rather than being directly proportional)

ΔP∝K1*(Vdot)^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When does the driving pressure need to be higher? Why?
a) to drive turbulent flow
b) to drive laminar flow

A

a) to drive turbulent flow (it is a more inefficient type of flow)

Because the driving pressure needed to maintain the same flow rate for turbulent flow is proportional to the square of the flow rate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which type of flow is more energetically efficient?

A

Laminar flow - you can achieve a greater flow rate for the same driving pressure in laminar flow compared to turbulent flow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

During laminar flow, the driving pressure needed to generate a given amount of flow varies directly with … and inversely with…

A

During laminar flow, the driving pressure needed to generate a given amount of flow varies directly with the TUBE LENGTH and inversely with the FOURTH POWER OF THE TUBE RADIUS.

The longer the tube, the greater the driving pressure needed to maintain the same flow rate.

The greater the tube radius, the less pressure needed to maintain the same flow rate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

During laminar flow, if the radius of the tube is halved, the driving pressure must be increased…

A

the driving pressure must be increased by 16-fold to maintain the same amount of airflow.

ΔP∝ 1/(r^4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

When is laminar flow most likely to occur?

A

When flow rate is low and tube diameter is small (i.e. in smaller airways)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When is turbulent flow most likely to occur?

A

When flow rate is high and tube diameter is large (i.e. in larger airways like the trachea)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does a higher Reynold’s number indicate?

A

Higher Reynold’s number. = more turbulent flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can we make turbulent flow more laminar? What is the clinical advantage of doing so?

A

By giving patients a mixture of helium and oxygen (heliox).
You can improve the ability to breathe in a person with obstructed airways by giving them this mixture because it decreases the density of the gas and makes the airflow more laminar. This helps reduce airway resistance and facilitates breathing in patients with upper airway obstruction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is resistance?

A

Resistance is the energy cost of flow

20
Q

What is the formula for resistance?

A

R = ΔP/V dot

*V dot = flow rate

Only formula you need to know!

21
Q

Resistance is determined by…

A
  • tube geometry
  • physical properties of gas or fluid
22
Q

For Poiseuille (laminar) flow, resistance is inversely proportional to …

A

the 4th power of the radius

(i.e. even a small increase in radius can result in a large decrease in airway resistance, and vice versa)

23
Q

What are the two possible geometrical arrangements of tubes?

A

In parallel: side by side
In series: end to end

24
Q

Which of the following has a greater total resistance?

a) tubes connected in series (end to end)
b) tubes connected in parallel (side by side)

A

a) tubes connected in series (end to end) have a greater total resistance

25
Q

The dichotomous branching arrangement of the airways is what type of geometrical arrangement?

A

Parallel geometrical arrangement (tubes connected side by side)

26
Q

Why does the branching of the airways reduce resistance overall, even though the branching leads to increasingly smaller vessels?

A

Because the overall cross-sectional area of al the smaller tubes in the periphery of the lung is much greater than the cross-sectional area of the trachea, even though individual airways are getting smaller!

27
Q

How does the velocity of flow change as air moves down through the airways?

A

Velocity of flow decreases as the diameter of individual airways decreases (flow slows down). Also, resistance to flow decreases because the total cross sectional area increases. This favours laminar flow in the smaller peripheral airways,a i.e. flow becomes more energetically efficient.

28
Q

As lung volume increases, airways are pulled open by… (2)

A
  • alveolar attachments on the membraneous bronchioles
  • effect of negative intrathoracic pressure on airways
29
Q

When you are at low lung volumes (near RV), the airway resistance is higher than at higher lung volumes (near TLC). In other words, airway resistance changes with lung volume. Explain.

A

As you breathe in, the alveoli are filled with air and the lung parenchyma stretches out, which causes the alveolar attachments to pull on the membraneous bronchioles, which open further. This increases the diameter of the airways, reducing resistance.

This is referred to as the interdependence between the parenchyma and the airways

30
Q

During flow, what pressure gradient is used to calculate total pulmonary resistance?

A

Pressure gradient between the mouth (airway opening) and the pleural space.

31
Q

Total pulmonary resistance (TPR) has two components:

A
  1. Airways resistance
    - loss of energy as air flows through the airways
    - big effect on TPR
  2. Tissue resistance
    - loss of energy as tissue molecules move past each other with changes in lung volume
    - small effect on TPR
32
Q

The airways component of total pulmonary resistance is calculated by…

A

determining the gradient between the mouth (airway opening) and the alveoli (airways resistance, Raw)

33
Q

Which has a bigger effect on total pulmonary resistance?
a) airways resistance
b) tissue resistance

A

a) airways resistance

34
Q

Maximum expiratory flow depends on… (3)

A
  1. airways resistance
  2. elastic recoil of the lungs
  3. expiratory muscle strength (to some degree)
35
Q

Why expiratory muscle strength only to some degree

A

Once flow reaches a certain level, no matter how hard the expiratory muscles push, flow will not increase any further. This phenomenon is called flow limitation.

36
Q

Why is there an expiratory flow limitation?

A

Because airways are not metal tubes and can be compressed by the increase in pleural pressure.

As you expire air from the lungs, the pleural pressure becomes more and more positive. It compresses the airways (tubes), i.e. their radius decreases. Therefore, the airway resistance increases, making it harder to blow air out even when your muscles are pushing hard.

37
Q

During expiration, the airways become narrowed at different sites, creating …, also known as …
These sites contribute to flow limitation.

A

choke points AKA equal pressure points

38
Q

Describe the effort-dependent phase of forced expiration?

A
  • early in the forced expiration (at higher lung volumes)
  • blow harder and you get more airflow
39
Q

Describe the effort-independent phase?

A
  • occurs later during the forced expiratory maneuver
  • no matter how hard one blows, beyond a certain point there is no further increase in lung flow at that lung volume
40
Q

What are some secondary factors contributing to expiratory flow limitation?

A
  • the driving pressure diminishes as lung volume decrease and elastic recoil falls
  • pressure dissipates in the airways, as energy is lost overcoming resistance
  • airway resistance increases at lower lung volumes as the radius of airways decreases (alveolar attachments are less taut)
41
Q

What determines flow in the effort-independent portion of the flow-volume curve?

A
  • elastic recoil pressure of the lung
  • resistance of the airways
42
Q

When can we detect diseases that affect elastic recoil and/or airways resistance? Why?

A

They will be detectable on forced expiratory flow-volume curves. If we see that the effort independent part of the curve is abnormal, we can infer what might be wrong with the properties of the lung and airways (elastic recoil or resistance).

43
Q

What does the flow-volume loop not indicate?

A

The FEV1

(you need a time-volume curve to see the FEV1)

44
Q

What are the spirometry measures of emphysema (obstructive lung disease)?

A

Reduced peak expiratory flow
Decreased FEV1/FVC ratio
Lower than normal FEV1 and FVC
Higher than normal RV and TLC

45
Q

What are the spirometry measures of fibrosis (restrictive lung disease)?

A

Relatively preserved peak expiratory flow
Increased FEV1/FVC ratio
Lower than normal FVC
Lower than normal RV ad TLC

46
Q

Why is the peak expiratory flow relatively preserved during fibrosis?

A
47
Q

What are the spirometry measures of chest wall diseases?

A

Reduced peak expiratory flow
Variable FEV1/FVC ratio
Lower than normal FVC
Lower than normal TLC (RV variable)

*residual volume will tend to be increased because the patient will be unable to sustain the effort of expiration
* see graph in slides!

BLOCK B - RESPIRATION (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions