3.1.4 measuring lung volumes

Question 1

breathing rate

Answer 1

number of breaths per minute

Question 2

oxygen uptake

Answer 2

volume of oxygen absorbed by lungs in 1 minute

Question 3

tidal volume

Answer 3

volume of air inhaled & exhaled in 1 breath (usually measured at rest)

Question 4

vital capacity

Answer 4

greatest volume of air that can be expelled from lungs after deepest possible breath

Question 5

spirometer

Answer 5

device that can measure movement of air into/out of lungs

Question 6

describe a float-chamber spirometer & what happens during inspiration/expiration

Answer 6

• chamber of air/medical-grade oxygen floating on tank of water
• inspiration: air drawn from chamber & lid moves down
• expiration: air returns to chamber & raises lid
• movements recorded by datalogger
• carbon dioxide-rich air that’s exhaled is passed though chamber of soda-lime = absorbs it & allows measurement of oxygen consumption

Question 7

precautions when using a spirometer

Answer 7

• subject must be healthy & free from asthma
• soda lime fresh & functioning
• no air leaks in apparatus = invalid or inaccurate results
• mouthpiece sterilised
• water chamber not overfilled, otherwise may enter air tubes

Question 8

what does the total lung volume consist of

Answer 8

1. vital capacity - can be measured
2. residual volume - cannot be measured with spirometer

Question 9

how is vital capacity measured

Answer 9

taking deep breath & expiring all air possible from lungs

Question 10

what does vital capacity depend on

Answer 10

• size of person (esp. height)
• age & gender
• level of regular exercise

Question 11

usual region of vital capacity

Answer 11

2.5 to 5.0 dm3

(may rise above in trained athletes)

Question 12

residual volume

Answer 12

volume of air which remains in lungs, even after forced expiration
–> usually 1.5dm3

Question 13

typical tidal volume

Answer 13

0.5dm3

Question 14

name of data from spirometer

Answer 14

spirometer trace

Question 15

describe how you would calculate oxygen uptake from a spirometer trace

Answer 15

graph (a) = records person at rest
graph (b) = records (same) person during exercise

1. on trace (a), draw line from point A to horizontal axis (y) & another from point B to horizontal axis (y)
   - measure length of time between 2 points
2. measure difference in volume between points A & B
3. divide by time taken for this decrease (step 1)
4. unit = dm3 s-1
   = rate of oxygen uptake

Question 16

how do you calculate breathing rate from spirometer trace

Answer 16

1. count number of peaks in each minute

–> breathing rate at rest usually 12-14 breaths per minute

Question 17

factors causing increased oxygen uptake

Answer 17

• increased breathing rate
• deeper breaths

–> due to increased demand eg. exercise