Respiratory 3 & 4

Question 1

Define residual volume.

Answer 1

Air that the lung cannot dispel.
(the alveoli is always partially inflated as this makes it easier for the lung to inflate and provides a reservoir of air to allow gas exchange at all times)

Question 2

What is the term for the amount of air that can be expired from the lungs by determined effort after normal inspiration?

Answer 2

Expiratory reserve volume

Question 3

Define functional residual capacity.

Answer 3

The normal amount of air left after normal expiration.

It is the sum of the residual volume and the expiratory reserve volume.

Question 4

What is the term used to define the amount of air which enters the lung during normal inspiration?

Answer 4

Tidal volume.

The same amount will leave the lung during expiration.

Question 5

Define the term inspiratory reserve volume.

Answer 5

The amount of air inhaled above the tidal volume upon taking a deep breath.

Question 6

What is the term used to define the maximum amount of air that can be inspired?

Answer 6

The inspiratory capacity.

It is the sum of the tidal volume and the inspiratory reserve volume.

Question 7

Define the term vital capacity.

Answer 7

The maximum amount of air that can be expired.

It is the sum of the expiratory reserve volume, the tidal volume and the inspiratory reserve volume.

Question 8

What is the term used to define the sum of the vital capacity and the residual volume?

Answer 8

Total lung capacity

Question 9

What is anatomical dead space?

Answer 9

Air that fills the conducting airways upon inspiration that will be exhaled without undergoing gas exchange.
It is usually 150ml.

Question 10

What are the two types of ventilation?

Answer 10

• pulmonary (minute) ventilation

- alveolar ventilation

Question 11

What is pulmonary ventilation?

Answer 11

The total air movement into/out of the lungs.

Question 12

What is alveolar ventilation?

Answer 12

The fresh air that reaches the alveoli and therefore is available for gas exchange.
(This is functionally more significant than pulmonary ventilation)

Question 13

What must be taken into account in order to calculate the alveolar ventilation?

Answer 13

The anatomical dead space.

Question 14

What occurs as a result of hyper-ventilation?

Answer 14

• increased alveolar ventilation
• PO2 rises
• PCO2 falls

Question 15

Is the feeling of ‘breathlessness’ more susceptible to changes in oxygen or carbon dioxide?

Answer 15

Carbon dioxide

Question 16

What is surfactant and what is it’s function?

Answer 16

A detergent-like fluid produced by type II alveolar cells.

It reduces surface tension on the alveolar surface membrane.

Question 17

What does the term surface tension refer to and where does it occur?

Answer 17

Surface tension refers to the attraction between water molecules.
It occurs wherever there is an air-water interface.

Question 18

How does surfactant combat surface tension?

Answer 18

Surface tension creates an inwardly directed pressure that wants to collapse the alveoli.
Surfactant negates this by sitting in-between the water molecules and reducing the directed pressure, and therefore increasing lung compliance.

Question 19

Is there greater pressure in smaller alveoli or larger alveoli?

Answer 19

There is greater pressure in smaller alveoli.

Question 20

Why do premature babies suffer Infant Respiratory Distress Syndrome?

Answer 20

Babies born before 36 weeks gestation have incomplete surfactant production, meaning the pressure required to inflate the alveoli is too great.

Question 21

How is IRDS treated?

Answer 21

Synthetic surfactant administered via aerosols.

Question 22

What are the lungs filled with in utero?

Answer 22

Saline

This means there is no surface tension to overcome.

Question 23

What is compliance?

Answer 23

The change in volume relative to the change in pressure.

ie. how much volume changes for any given pressure

Question 24

Define high compliance.

Answer 24

A large increase in lung volume for a small decrease in intrapleural pressure.

Question 25

Define low compliance.

Answer 25

A small increase in lung volume for a large decrease in intrapleural pressure.

Question 26

Would healthy lungs have high or low compliance?

Answer 26

High compliance

Question 27

Why does it require a greater change in pressure to reach a particular lung volume during inspiration than expiration?

Answer 27

• inspiration must overcome surface tension (active)

- normally the work of inspiration is recovered as elastic recoil during expiration (passive)

Question 28

Briefly define emphysema.

Answer 28

The loss of elastic tissue meaning that expiration requires effort.

Question 29

Briefly define fibrosis.

Answer 29

Fibrous tissue is laid down meaning that the effort of inspiration increases.

Question 30

Where in the lung usually has the greatest compliance?

Answer 30

The base of the lung.

Question 31

Where in the lung usually has the least compliance?

Answer 31

The apex of the lung.

Question 32

Why does compliance vary around the lung?

Answer 32

The main reason is gravity.
The alveoli at the base of the lung will expand more on inspiration as they are the most deflated on exhalation and therefore there is the greatest pressure change.

Question 33

What technique is commonly used to measure lung function?

Answer 33

Spirometry

Question 34

Define static spirometry.

Answer 34

Only the volume of the expiration is considered.

Question 35

Define dynamic spirometry.

Answer 35

The time taken to exhale a certain volume is considered.

Question 36

What cannot be measured by spirometry?

Answer 36

• residual volume

- functional residual capacity