Session 2 - part II

Question 1

What is the partial pressure of O2 in alveolar air?

Answer 1

13.3 KPa (Atmospheric is 21 KPa)

Question 2

What is the partial pressure of CO2 in alveolar air?

Answer 2

5.3 KPa (Atmospheric is tiny <1)

Question 3

What is the partial pressure of O2 and CO2 in venous blood?

Answer 3

6.0 KPa O2 & 6.5 KPa CO2 (at rest)

These values vary with different levels of metabolism

Question 4

What causes O2 to diffuse into the blood?

Answer 4

The partial pressure of O2 in the alveolar gas is greater than the partial pressure of O2 in the returning blood.

Question 5

What causes CO2 to diffuse into the alveoli?

Answer 5

The partial pressure of CO2 in the alveolar gas is lower than the partial pressure of CO2 in the returning blood.

Question 6

What does diffusion of gases depend on?

Answer 6

Area
Gradients
Dsitance

Question 7

What does resistance to diffusion depend on?

Answer 7

Nature of the barrier

Nature of the gas

Question 8

How does the barrier effect gas exchange in the alveoli?

Answer 8

The gas has to diffuse through other gases and the alveolar wall which has;
Simple squamous epithelium
Tissue fluid
Simple squamous of the vessel
Plasma
Membrane of the red blood cell

Question 9

Diffusion of gases through gases is inversely proportional to what?

Answer 9

Molecular weight

Question 10

Which molecule is heavier out of CO2 & O2?

Answer 10

CO2 is heavier

Question 11

Which molecule is more soluble out of CO2 & O2?

Answer 11

CO2

Question 12

What gas transports the fastest?

Answer 12

CO2 so exchange of O2 is always limiting

Question 13

How thick is the barrier for oxygen transport in the alveoli?

Answer 13

0.6 micro meters

Question 14

How can you determine the gas composition in the alveoli?

Answer 14

Take a sample from an artery in the wrist, the partial pressures will be the same here as in the alveoli

Question 15

Define ventilation

Answer 15

Expansion of the lungs which increases the volume of the respiratory bronchioles and alveolar ducts so air can flow down the airways to them.

Question 16

Which parts of the airways can/cannot expand?

Answer 16

Can - Respiratory bronchioles, alveolar ducts

Cannot - Rest of respiratory system

Question 17

How can you measure the ventilation?

Answer 17

A spirometer - Patient breathes from a closed chamber (Pressure held constant) over water whose volume changes with ventilation

Question 18

Define Tidal volume

Answer 18

Volume in and out of the same airways with each breath

Question 19

Define Inspiratory reserve volume

Answer 19

The extra volume that can be breathed in over the Tidal volume at rest

Question 20

Define Expiratory reserve volume

Answer 20

The extra volume that can be breathed out over the Tidal volume at rest

Question 21

Define Residual volume

Answer 21

The volume left in the lungs at maximum expiration.

Question 22

How do you measure Residual volume?

Answer 22

Using Helium dilution, not a spirometer

Question 23

Why do lung capacities not vary?

Answer 23

They’re measured from fixed points in the breathing cycle, so better clinically as they are always the same as always taken at the same point.

Question 24

Define Vital capacity

Answer 24

Maximum inpsiration to maximum expiration.
The biggest breath that can be taken and is often effected in disease
Usually 5L

Question 25

Define Inspiratory capacity

Answer 25

The biggest breath that can be taken from resting expiratory level
Usually 3L

Question 26

Define Functional residual capacity

Answer 26

Volume of air in the lungs at resting expiratory level.
Usually 2L
Expiratory reserve + Residual volume

Question 27

Define Ventilation rate

Answer 27

Amount of air moved in and out of a space per minute. It is the product of volume moved per breath and respiratory rate

Question 28

Define Pulmonary ventilation rate

Answer 28

Tidal volume x Respiratory rate

Question 29

What is Dead space?

Answer 29

Due to the air entering and leaving the system via the same airways, the last air stays in the airways and is the first air out. Therefore it never reaches the alveoli and is wasted.

Question 30

What is the alveolar ventilation rate?

Answer 30

The amount that reaches the alveoli

Dead space is taken into account

Question 31

Define Serial dead space

Answer 31

The volume of the airways
Measured using a nitrogen washout
Usually 0.15L

Question 32

Define Distributive dead space

Answer 32

Parts of the lung which are not airways, but don’t support gas exchange due to being dead, damaged or having poor perfusion.

Question 33

What is Physiological dead space?

Answer 33

Distributive dead space + Serial dead space

Usually 0.17L

Question 34

How do you calculate dead space ventilation rate?

Answer 34

Dead space volume x Respiratory rate (number of breaths per min)

Question 35

What type of breathing is most work, but gets most air to the alveoli?

Answer 35

Deep breathing

Question 36

What is the standard Tidal volume?

Answer 36

0.5L

Question 37

What is Pulmonary ventilation rate?

Answer 37

Tidal Volume x Respiratory Rate

Question 38

What is the standard Inspiratory volume?

Answer 38

2.5L

Question 39

What is the standard Residual volume?

Answer 39

0.8L

Question 40

What is the standard Expiratory volume?

Answer 40

1.5L

Question 41

What is the standard Functional residual capacity?

Answer 41

2.3L

Question 42

What is the standard Inspiratory capacity?

Answer 42

3.0L

Question 43

What is the standard Vital capacity?

Answer 43

5.0L

Question 44

What is the standard Lung capacity?

Answer 44

5.8L