Measuring lung volumes 3.1.4

Question 1

What does a spirometer measure?

Answer 1

It is used to measure lung volume, it measures the movement of air in and out of the lungs as a person breathes

Question 2

What is the mechanism of a spirometer?

Answer 2

• During inspiration, air is drawn from the chamber so that the lid moves down.
• During expiration, air returns to the chamber, raising the lid
• These movements are recorded on a data logger
• The carbon dioxide rich air exhaled is passed through a chamber of soda lime, which absorbs the carbon dioxide - this enables an oxygen consumption to be measured

Question 3

Name 3 precautions that should be used when using a spirometer

Answer 3

• Soda lime should be fresh
• Subject should be asthma free and healthy
• The water chamber should not be overfilled

Question 4

What does the total lung volume consist of?

Answer 4

The vital capacity and the residual volumes

Question 5

Define vital capacity

Answer 5

• The maximum volume of air that can be moved by the lungs in one breath.

Question 6

What is the average vital capacity?

Answer 6

In the region of 2.5 - 5.0 dm3

Question 7

What does vital capacity depend on?

Answer 7

• The persons size
• Their age and gender
• Their level of regular exercise

Question 8

Define residual volume

Answer 8

The volume of air that remains in the lungs even after forced expiration.

Question 9

What is the approximate residual volume?

Answer 9

1.5 dm3

Question 10

Define tidal volume

Answer 10

The volume of air moved in and out with each breath
- Normally measured at rest

Question 11

What is the typical tidal volume at rest?

Answer 11

0.5 dm3

Question 12

What is breathing rate at rest, per minute?

Answer 12

12 - 14 breaths per minute