Lung statics 2

Question 1

What are the 3 determinants of lung volume?

Answer 1

1. pulmonary compliance
2. chest wall compliance
   3.

Question 1

Define the transpulmonary pressure

Answer 1

Difference in the airway opening pressure (mouth) and intrapleural pressure

Question 2

The more compliant the lung, the …
a) looser it is
b) stiffer it is

Answer 2

a) looser it is

Question 3

What is the formula for compliance?

Question 4

When there is no flow, the pressure at the airway opening should be the same as …

Answer 4

alveolar pressure

Question 5

Why is the pressure-volume cuve different between inspiration and exhalation? What is this difference called?

Answer 5

Hysteresis

Question 6

How does emphysema/COPD affect elastic recoil of the lungs?

Answer 6

Loss of elastic recoil i.e. increased compliance

Make sure you can draw the emphysema PV curve compared to normal.

Question 7

How does pulmonary fibrosis affect elastic recoil of the lungs?

Answer 7

Increased lung stiffness i.e. decreased compliance.

Make sure you can draw the pulmonary fibrosis PV curve compared to normal.

Question 8

What are the 3 determinants of compliance?

Answer 8

1. Tissue forces (lung)
2. Surface tension
3. Compliance of the chest wall

Question 9

What do tissue forces in the lung arise from?

Answer 9

From the elastin-collagen-proteoglycan network of the lung tissue and the elastic recoil of the lung tissue.

Question 10

Lungs have a tendency to want to…

Answer 10

deflate

Question 11

What can decrease tissue forces in the lung?

Answer 11

Destruction of lung parenchymal architecture (emphysema)

Question 12

What can increase tissue forces in the lung?

Answer 12

Lung scarring (fibrosis)

Question 13

Surface tension occurs at the …. of the alveoli.

Answer 13

air-liquid interface

Question 14

Surface tension arises from…

Answer 14

the tendency of the liquid molecules to stick together rather than to associate with air molecules - will cause the alveoli to collapse

Question 15

What prevents the alveoli from collapsing under their surface tension?

Answer 15

Pulmonary surfactant, which modifies surface tension

Question 16

What is surfactant composed of?

Answer 16

Small layer of phospholipids

Question 17

What happens when lungs are filled with saline?

Answer 17

Air-liquid interface is lost , resulting in the loss of surface tension and therefore less elastic recoil (the lung no longer wants to collapse on itself) and increased compliance.

Question 18

Why is surface tension important for adequate function of the lungs?

Question 19

The smaller the radius of the alveoli, the … the surface tension
a) greater
b) smaller

Question 20

The smaller the radius of the alveoli, for the same surface tension, the … the pressure inside the alveoli
a) greater
b) smaller

Answer 20

a) greater

Smaller alveolus = greater intra-alveolar pressure

Question 21

Decsribe Laplace’s law on surface tension and alveolar instability

Question 22

If you are at RV (maximum forceful expiration), how does the chest wall react?

Answer 22

Chest wall wants to expand

Question 23

When you are at FRC, how does the chest wall want to react?

Answer 23

The chest wall wants to expand, while the lungs (pulmonary tissue) want to deflate. This leads to an equilibrium…

Question 24

As opposed to the lungs, the chest wall always has a tendency to …

Answer 24

expand

Question 25

When you are at TLC (maximum inspiration), how does the chest wall want to react?

Answer 25

Once around 60-80% of the TLC is reached, it no longer wants to expand - it wants to contract (and so do the lungs) - this really helps drive expiration after a big breath.

Question 26

The lung always wants to deflate (always exerts a positive pressure). Te chest wall usually wants to expand (exerts a negative pressure) until you reach 60-80& of the TLC, at which point it wants to contract (exerts a positive pressure)

Answer 26

Review pressure graph (blue, green, red curves and the different pressures…)

Question 27

What are the 3 main determinants of the residual volume (what makes it different from person to person)?

Answer 27

1. Limits of the chest wall (youth)
2. Premature airway closure (due to age-related loss of elastic recoil)
3. Limit of expiratory force

Question 28

How does age affect elastic recoil? How does this affect the time needed to empty the lungs?

Answer 28

Loss of elastic recoil with age (proteoglycan network affected) - > small airways are more easily collapsed - > takes longer to empty lungs

Question 29

How does the limit of expiratory force affects the RV?

Answer 29

If you can’t expire with much force, you will have a greater residual volume than someone capable of expiring with greater force.

Question 30

Why is it that when small airways collapse more easily due to loss of elastic recoil it takes longer to empty lungs?

Answer 30

???

Question 31

Explain regional differences in compliance in the lungs.

Answer 31

The weight of the lungs causes the lower zone of the lungs to have smaller resting volumes. However, the lower zone of the lungs are more easily ventilated as they are at the steeper part of the P/V curve. ?????

Question 32

At TLC, both the upper and lower part of the lung are maximally inflated….

Question 33

At RV, both the upper and lower part of the lungs are maximally deflated…