Lung Volumes And Lung Function Testing

Question 1

What happens to the lung at high pressure?

Answer 1

Lung stiffer, low compliance

Question 2

What conditions cause decrease compliance in the lungs?

Answer 2

Alveolar oedema, pulmonary fibrosis etc…

Question 3

What factors are needed for efficient ventilation?

Answer 3

High lung compliance

Low alveolar surface tension (due to surfactant)

Question 4

Define TV, IRV, ERV, VC, RV, FRC and TLC

Answer 4

Tidal volume: volume of air entering and leaving the lung on each normal breath (0.5L)
Inspiratory reserve volume: extra volume of air inspire above the normal TV with full force
Expiratory reserve volume: extra volume of air expired by forceful expiration at the end of normal tidal expiration
Vital capacity: max amount of air expelled from the lungs after filling lungs to a max and expelling it to the max ( TV + ERV + IRV)
Residual volume: volume of air present in lungs after forceful expiration
Functional residual capacity:amount of air in lungs after normal expiration (ERV + RV)
Total lung capacity: max volume of air the lungs can hold ( VC + RV)

Question 5

How does one calculate FRC, TLC and RV?

Answer 5

Helium dilution and nitrogen wash out

Question 6

What are the characteristics of a restrictive deficit?

Answer 6

Reduced Forced vital capacity
Normal FEV1
Ration normal or increased

Question 7

What are the characteristics of an obstructive deficit?

Answer 7

Reduced FEV1
normal FVC
reduced ration FEV1/FVC

Question 8

Explain the concept of peak expiratory flow

Answer 8

PEF is a person’s maximum speed of expiration. It is measured with a peak flow meter.
The flow volume curve has 2 phase: effort dependent (TLC to PEF) and effort independent phase (PEF to RV).

Question 9

Explain the flow volume curve and Peak Expiratory Flow Rate

Answer 9

Person breathe in to TLC and forcefully breathe out. a peak is obtained at end of effort dependent phase as air primarily moves from the larger airways. then it becomes effort independent

Question 10

Explain flow volume loop in obstructive and restrictive deficits

Answer 10

Same shape as normal in restrictive, only shit to right as volumes are decreased
Scooping in obstructive due to air not being able to come out of the narrower airways. Can’t exhale effectively so retain air in lungs. So higher residual volume

Question 11

How do you test for gas transfer?

Answer 11

By diffusion conductance. Measure how easily CO crosses form alveolar air to blood