Ventilation & Compliance

Question 1

What is tidal volume?

Answer 1

The air displaced between inspiration and exhalation (around 500mL)

Question 2

What is residual volume?

Answer 2

Volume of air that always remains in the lungs. 1) Stops alveoli collapsing at end of respiration 2) Provides reservoir of air that allows gas exchange too occur all the time (around 1200mL)

Question 3

What is functional residual capacity?

Answer 3

Amount of air in lungs at the end of normal relaxed expiration. Helps to maintain potency of airways - stops the collapse of smaller airways. Reduced by a number of anaesthetics.

Question 4

What is vital capacity?

Answer 4

Maximum amount of air that can be shifted in one breath. (Breathe in and out as much as possible). Tidal volume + expiratory reserve volume + inspiratory reserve volume (around 4600mL)

Question 5

What is pulmonary ventilation?

Answer 5

Total air movement into/out of lungs

Question 6

What is alveolar ventilation?

Answer 6

Fresh air betting to alveoli and therefore available for gas exchange

Question 7

Define partial pressure

Answer 7

The pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture.

Question 8

What is the function of surfactant

Answer 8

Reduces surface tension on alveolar surface membrane - reducing tendency for alveoli to collapse

Question 9

What is/Where does surface tension occur?

Answer 9

Occurs at air-water interface ad refers to interaction between water molecules

Question 10

What is compliance?

Answer 10

Change in volume relative to change in pressure - it represents stretchability of the lungs. Changes in disease/age

Question 11

What is high/low compliance?

Answer 11

High compliance = large increase in lung volume for a small decrease in ip pressure
Low compliance = small increase in lung volume for large decrease in ip pressure

Question 12

Expiration or inspiration requires a greater change in pressure from FRC to reach a particular volume?

Answer 12

Inspiration

Question 13

Why does expiration require a lesser change in pressure from FRC to reach a particular volume

Answer 13

Due to elastic recoil as work of inspiration is recovered during expiration (passive)

Question 14

How does emphysema effect work of respiration?

Answer 14

Loss of elastic tissue means expiration requires effort

Question 15

How does fibrosis effect work of respiration?

Answer 15

Inert fibrous tissue means effort of inspiration increases.

Question 16

Describe obstructive lung disease?

Answer 16

Obstruction of air flow especially on expiration - increased airway resistance e.g. Asthma & COPD

Question 17

Describe restrictive lung disease?

Answer 17

Restriction of lung expansion - loss of lung compliance & incomplete lung expansion.

Question 18

What is chronic bronchitis?

Answer 18

Type of COPD which involves inflammation of bronchi

Question 19

What is emphysema?

Answer 19

Type of COPD which involves the destruction and loss of elasticity of alveoli e.g. fibrosis, infant respiratory distress syndrome, oedema, pneumothorax

Question 20

What is fibrosis?

Answer 20

Type of restrictive disease that involves the formation of excessive fibrous connective tissue (Idiopathic or Asbestosis

Question 21

Describe spirometry

Answer 21

Technique used to measure lung function:
Static - only consideration made is the volume exhaled
Dynamic - time taken to exhale a certain volume is being measured

Question 22

What volumes can be measured by spirometry?

Answer 22

• tidal volume
• IRV
• inspiratory capacity
• vital capacity
• ERV

Question 23

What is FEV1?

Answer 23

Forced Expiratory Volume in 1 sec = 4.0L healthy males

Question 24

What is FVC?

Answer 24

Forced Vital Capacity = 5.0L in healthy males