Lung Physiology 2: Lung function Tests

Question 1

What is the tidal volume? (TV)

Answer 1

Tidal volume – volume inhaled/exhaled in a normal breath, ~500ml

Question 2

What is the inspiratory reserve? (IRV)

Answer 2

Inspiratory reserve – max air that can be inhaled minus tidal volume, ~3L

Question 3

What is the expiratory reserve? (ERV)

Answer 3

Expiratory reserve – max air that can be exhaled minus tidal volume, ~1.2L

Question 4

What is the residual volume? (RV)

Answer 4

Residual volume – air remaining in lungs after max expiration to prevent collapse, ~1.2L

Question 5

What is the vital capacity? (VC)

Answer 5

Vital capacity – max air expired after max inspiration, ~4.7L (ERV +TV + IRV)

Question 6

What is the Inspired capacity? (IC)

Answer 6

Insp. capacity – max inhalation after normal tidal expiration, ~3.5L (IRV + TV)

Question 7

What is the functional residual capacity? (FRC)

Answer 7

Functional residual capacity – air in lungs after tidal expiration, ~2.4L (RV + VC)

Question 8

What is the total lung capcity? (TLC)

Answer 8

Total lung capacity – DUH… 5.9L (RV +VC)

Question 9

How do we measure a lung function with a machine?

Answer 9

• Attached to system where air is coming in and out, moving a fixed level of water
• Charts changes in volume as you breath; as water vapour replaces exactly O2

Question 10

What is FEV1?

Answer 10

the forced expiratory volume in one second (80% of vital capacity in healthy person)

Question 11

What is the PEF?

Answer 11

peak air flow – highest velocity of air measured during FVC. Flow will then decrease linearly in healthy person after PEF
- Measured with a spirometer

Question 12

What is the FVC?

Answer 12

forced vital capacity – max air expired under max force after max inspiration

Question 13

How do you measure the FEV1?

Answer 13

• Breathe in to TLC
• Exhale as fast as possible to RV
• Volume produced is the FVC

Question 14

How is carbon monoxide used to estimate TLCO

Answer 14

TLCO - the transfer capacity of the lung, for the uptake of carbon monoxide (CO)
Measuring efficiency of gas exchange. Known [CO] inhaled, 10 sec breath hold, expired [CO] measured. Reduced with COPD

Question 15

What does a low FVC and FEV1 indicate?

Answer 15

Airway restriction e.g. pulmonary fibrosis

Question 16

What does a low FEV1 indicate?

Answer 16

Airway obstruction (when the FVC ratio is similar)
e.g. COPD and asthma