L14

Question 1

what is inspiration

Answer 1

Inspiration – active process, requires the
active involvement of diaphragm and
external intercostal muscles

Question 2

what is expiration

Answer 2

Expiration – passive process at rest, due
to elastic recoiling which pulls the thorax
inwards and relaxed diaphragm inwards

Question 3

describe the events during inspiration

pressures

Answer 3

diaphragm and inspiratory intercostals contract causing the thorax to expand

Pip becomes more subatmospheric (more negative)

transpulmonary pressure increases causing the lungs to expand

Palv becomes subatmospheric (more -ive) because they start to expand causing air to flow into the alveoli (increase in volume = decrease in pressure)

Question 4

describe the events during expiration

Answer 4

diaphragm and inspiratory intercostals stop contracting causing the chest wall to recoil inward

Pip starts to move towards preinspiration value

transpulmonary pressure moves back to preinspiration value

lungs recoil back to preinspiration size

air in alveoli become compressed causing alveolar pressure to become greater than atmospheric pressure causing air to flow out of the lungs

Question 5

If Patm=0 mmHg and Palv = 4 mmHg, then

A) Transpulmonary pressure is -4 mmHg

B) It is the end of the normal expiration and there is no
airflow

C) Transpulmonary pressure is +4 mmHg

D) It is the end of the normal inspiration and there is
no air flow

E) Air is flowing out of the lung

Answer 5

E

Question 6

what work has to be done in the work of breathing

Answer 6

overcome the elestic properties of the lungs (stiffness)

overcome airway resistance

Question 7

what are the 2 things that contribute to the stiffness of the lungs

Answer 7

compliance and surfactant

Question 8

what is lung compliance

Answer 8

A measure of elastic property of the lung, compliance is the
inverse of stiffness

Defined as the magnitude of the change in the lung volume (ΔVL) produced by the given change in the transpulmonary
pressure (ΔPtp)

Question 9

what is the equation for compliance in the lungs

Answer 9

CL = ΔVL ⁄ ΔPtp

Question 10

what are the 2 compliance curves

Answer 10

Inspiratory compliance curve

Expiratory compliance curve

Question 11

the less compliance the lungs have the more work you have to do to expand the lungs

what are some diseases associated with this

Answer 11

emphysema = increase in lung compliance

fibrosis = decrease in lung compliance

Question 12

how do we overcome surface tension at the fluid gas interface

Answer 12

surfactant

Question 13

what creates the surface tension

Answer 13

The alveolar wall is lined with water molecules which always try and bond together (polar forces)

They are always trying to connect to each other therefore the water prevents the alveoli from expanding. They are always trying to collapse the alveoli

Question 14

what cells produce surfactant

Answer 14

alveolar type II cells

Question 15

what is the major constituent of surfactant

Answer 15

phospholipids

This is made of proteins and phospholipids but mainly phospholipids

Question 16

how does surfactant lower surface tension

Answer 16

Reduces attractive forces between
fluid molecules lining alveoli.

Surface tension in alveoli is reduced.

Easier to increase lung size i.e. increased compliance

This prevents the smaller alveoli from collapsing. The alveoli are all different sizes therefore the smaller ones the water is closer together and they are more likely to collapse smaller alveoli

Question 17

what is it called when surfactant is absent in premature babies

Answer 17

respiratory distress syndrome (RDS)

Question 18

what happens when you are sitting down in terms of surfactant

Answer 18

When you are sitting down the lungs become more stiff therefore you stimulate more surfactant

Question 19

what is the treatment for respiratory distress syndrome (RDS)

Answer 19

Therapy is – assisted ventilation and administration of natural or synthetic surfactant given through the infant’s trachea

Question 20

Surfactant:

A. lowers surface tension at the fluid-gas interface of the
alveoli

B. stabilizes the smaller alveoli, thereby preventing them
from collapsing due to high pressure.

C.is a mixture of both lipids and protein, but its major
component is protein.

D. All of A, B and C are correct.

E. Only A and B are correct.

Answer 20

E

Question 21

how can you describe air flow during quiet breathing

Answer 21

Air flow is mainly laminar flow during quiet breathing

Question 22

what is resistance to flow determined by

Answer 22

Poiseuille’s Law

R is inversely proportional to r^4

Question 23

what are inportant elements for airway resistance

Answer 23

Bronchoconstriction / bronchodilation

Question 24

what does cystic fibrosis and asthma have to do with airway resistance

Answer 24

We don’t inhale is viscous air but in cystic fibrosis we secrete more mucus

Bronchi restriction is in asthma is when these constrict

Question 25

where is the main area of airway resistance

Answer 25

in the larger bronchi

Most of the resistance to airflow arises in the the first 6 generations of the airway.

This is why asthma is called bronchiolar asthma

Question 26

why do we have higher in larger airways

Answer 26

Airflow Velocity decreases substantially as the effective cross-sectional area increases.

Airway generations exist in parallel rather than in series (in vascular system arterioles are arranged in series).

Question 27

what factors affect airway resistance under normal conditions

Answer 27

Lung volume
- increases during inspiration (due to
increase in transpulmonary pressure). this causes the airway radius to
become larger → decreasing airway resistance → lung
expands

Radial traction
- pulling of adjacent alveoli – reduces airway resistance

Question 28

what diseases affect airway resistance

Answer 28

Asthma

Chronic obstructive pulmonary disease (COPD) such as

• Emphysema
• Chronic Bronchitis

Question 29

know the work of breathing pressure volume loops

Answer 29

you need to look at the diagragm at the end of the lecture

Question 30

what does the pressure volume loop provide us with information about

Answer 30

the compliance of the lung

Question 31

what effect does a restrictive lung disease have on airway resistance

Answer 31

there is no change in airway resistance

Question 32

what effect does a restrictive lung disease have on lung compliance

Answer 32

Lung compliance decreased mening more work needs to be done to overcome elastic resistance and non elastic resistance

Question 33

how does a decrease in lung compliance affect the pressure volume curve

Answer 33

it shifts it to the right

Question 34

what effect does a restrictive lung disease have on intrapleural pressure

Answer 34

A more negative Pip required to move the same amount of air (inspiratory flow rates), increases the work of breathing

Question 35

what effect does a obstructive lung disease have on lung compliance

Answer 35

no change in lung compliance

Question 36

what effect does a obstructive lung disease have on airway resistance

Answer 36

it increases airway resistance

Question 37

when is emphysema

Answer 37

it is an obstructive lung disease

is when the alveoli flusses to become flaccid (they don’t recoil)

This means that you don’t need as much energy to expand the lung

However there is less elastic recoil so you have to spend more energy to push the lung back to its original position meaning that you will have to do more work breathing out (wont be a passive process)

causes you to do more work than if your system was working normally

Question 38

what effect does a obstructive lung disease have on pressure volume loops

Answer 38

Similar work to overcome elastic resistance

More work to overcome non-elastic resistance, inspiration

More work to overcome non-elastic resistance, expiration

A more positive
expiratory pressure is required causing expiration to become an active process

Question 39

what effect does a obstructive lung disease have on intrapleural pressure

Answer 39

A more negative intra pleural pressure (Pip) required to move the same amount of
air

Question 40

Which of the following statements are correct regarding airway
resistance?

(i) . Airflow velocity decreases as the size of the airways become smaller, hence the highest resistance is seen in the respiratory bronchioles.
(ii) Air way resistance is inversely related to the fourth power of the radius (r4).

(iii). In healthy individuals, inspiration reduces the airway
resistance due to an increase in the transpulmonary
pressure (Ptp).

(iv). Asthma increases airway resistance.

A. (i), (iii) and (iv) are correct.

B. (ii), (iii), (iv) are correct.

C.(i), (ii) and (iv) are correct.

D. only (ii) and (iii) are correct.

E. all of the above are correct

Answer 40

B. (ii), (iii), (iv) are correct.

i should say large bronchi

Question 41

Lung compliance is increased in emphysema

BECAUSE

chronic emphysema increases airway resistance.

Answer 41

obstructive causes no change in lung complacence

but emphysema does

therefore both statments are true but not causal