L15 - Respiration 2

Question 1

Which factors affect airway resistance? What is the main determinant?

Answer 1

length of the system, viscosity of air and diameter of airways
diameter of airways is the main determinant because this factor can be controlled

Question 2

What is the work of breathing affected by?

Answer 2

airway resistance and lung compliance

Question 3

What is lung compliance? How does lung compliance affect work of breathing?

Answer 3

lung compliance is the ability of lung to stretch and therefore, decreased lung compliance = increased work of breathing

Question 4

What is lung elastance?

Answer 4

ability of lung to spring back after being stretched

Question 5

If lung compliance increases, then lung elastance will also always increase. (true/false)

Answer 5

false

Question 6

In what cases does lung compliance decrease?

Answer 6

decreases in diseases such as pulmonary fibrosis when inelastic scar tissue is formed

Question 7

In what cases does lung elastance decrease?

Answer 7

decreases in diseases such as emphysema when elastin fibres in lung are destroyed

Question 8

How does alveolar surface tension affect lung compliance?

Answer 8

surface tension due to hydrogen bonds between water molecules which resist any force that increases its surface area, thus opposes expansion of alveolus creating surface tension
also, liquid surface area tends to shrink due to attraction between water molecules, thus reducing alveolus size

Question 9

What is the Law of LaPlace? How does this relate to breathing?

Answer 9

if two bubbles have the same surface tension, the small bubble will have a higher pressure i.e. small alveolus would have increased resistance to stretch and increased work of breathing

Question 10

What prevents alveoli from collapsing?

Answer 10

surfactant and alveolar interdependence

Question 11

What is surfactant and how does it affect breathing?

Answer 11

surface active agents which disrupt cohesive forces between water molecules and replace water at the surface (decreases surface tension and resistance of lung to stretch)

Question 12

How are smaller alveoli able to stretch just as much as larger alveoli?

Answer 12

surfactant is more concentrated in smaller alveoli

Question 13

What is alveolar interdependence and how does it affect breathing?

Answer 13

alveoli are interconnected so collapsing alveoli stretch surrounding alveoli and when surrounding alveoli recoil this pulls the collapsing alveoli back open

Question 14

What are two categories of respiratory disease?

Answer 14

obstructive and restrictive lung disease

Question 15

What is obstructive lung disease? Give some examples.

Answer 15

narrowing of lower airways and increased airway resistance
more difficult to expire
e.g. asthma, emphysema, chronic bronchitis

Question 16

What is restrictive lung disease? Give some examples.

Answer 16

decrease in lung compliance and increased difficulty of inflating lung
e.g. pulmonary fibrosis

Question 17

What does a spirometer do?

Answer 17

measures lung volumes and capacities

Question 18

Do we really know what the residual volume (RV) is? Can we measure it with spirometry?

Answer 18

no, it can only be estimated with spirometry

Question 19

What can residual volume be measured with?

Answer 19

with a helium dilution method

Question 20

Why is expiration more affected than inspiration when there is an issue with passage of air?

Answer 20

because we have more muscles dedicated to inspiration

Question 21

How does obstructive lung disease affect FEV1/FVC ratios?

Answer 21

decreases FEV1/FVC ratios

Question 22

What is FEV1?

Answer 22

the amount of air breathed out during the first second of forced expiration

Question 23

What is FVC?

Answer 23

the amount of air breathed out after the fifth second of forced expiration

Question 24

What is a normal FEV1/FVC ratio?

Answer 24

around 80%

Question 25

Which one/s of the following will NOT decrease with an obstructive lung disease? (FEV1, FVC, FEV1/FVC ratio, vital capacity, residual volume, total lung capacity, none of the above)

Answer 25

residual volume and total lung capacity

Question 26

How does obstructive lung disease affect the lungs?

Answer 26

severely reduced FEV1, reduced FVC, reduced FEV1/FVC ratio, reduced vital capacity, increased residual volume, no change in total lung capacity

Question 27

Which one/s of the following will NOT decrease with a restrictive lung disease? (FEV1, FVC, FEV1/FVC ratio, vital capacity, residual volume, total lung capacity, none of the above)

Answer 27

FEV1/FVC ratio and residual volume

Question 28

How does restrictive lung disease affect the lungs?

Answer 28

reduced FEV1, reduced FVC, increased or no change in FEV1/FVC ratio, reduced vital capacity, no change in residual volume and reduced total lung capacity

Question 29

What is anatomic dead space and what is the effect it has upon breathing?

Answer 29

conducting airways known as anatomical dead space e.g. trachea and bronchi
air in conducting airways is not available for gas exchange and therefore we have “wasted” ventilation which affects efficiency of breathing

Question 30

What is minute ventilation (Ve)?

Answer 30

total ventilation over a fixed time period - usually expressed per minute

Question 31

How is minute ventilation calculated?

Answer 31

Ve = tidal volume (TV) x frequency of ventilation (f)

Question 32

What is alveolar ventilation (Va)?

Answer 32

volume of alveolar air (tidal volume minus physiological dead space) exchanged per unit time

Question 33

Is there a ‘functional’ difference between TV of 0.15L / f = 40 and TV of 1.20L / f = 5?

Answer 33

yes, there is a big difference because in the first situation we are only exchanging the anatomic dead space