Pulmonary function tests

Question 1

What are pulmonary function tests?

Answer 1

• Tests that measure:
• Lung volumes
• Rate of airflow
• Gas exchange

Question 2

What are pulmonary function tests used for?

Answer 2

• Diagnose patients with respiratory problems
• Establish severity and progression of lung disease
• Assess treatment response
• Monitor patients on meds with lung toxicity

Question 3

What instruments and methods are used to carry out pulmonary function tests?

Answer 3

• Peak flow meter
• Spirometry
• Diffusing capacity for carbon monoxide
• Body plethysmography

Question 4

How is peak expiratory flow measured?

Answer 4

• Peak flow meter
• Measures maximum airflow rate attained during forced expiration
• Normal = >80% of predicted average value based on height, gender and age
• Useful in monitoring people with asthma
• Baseline is determined when patient is asymptomatic

Question 5

What is spirometry used for?

Answer 5

• Measures some lung volumes
• Calculates airflow as volumes are measured over time
• Produces graphical representations

Question 6

Define tidal volume

Answer 6

• Amount of air moving in and out of lungs at rest

Question 7

Define inspiratory reserve volume

Answer 7

• Additional amount of air can be inhaled after normal inspiration
• I.e. how much more air we can breathe in above tidal volume

Question 8

Define expiratory reserve volume

Answer 8

• Additional amount of air can be exhaled after normal expiration
• I.e. how much more air we can breathe out above tidal volume

Question 9

Define residual volume

Answer 9

• Amount of air remaining in lungs after maximal forceful expiration

Question 10

Define inspiratory capacity

Answer 10

• Total volume of air that can be inspired following a normal expiration (tidal volume + inspiratory reserve volume)

Question 11

Define functional residual capacity

Answer 11

• Volume of air present in lungs at end of passive expiration
• Expiratory reserve volume + residual volume

Question 12

Define total lung capacity

Answer 12

• Volume of air contained in lungs at end of a maximal inspiration
• Tidal volume + inspiratory reserve volume + expiratory reserve volume + residual volume

Question 13

Define vital capacity

Answer 13

• Volume of air exhaled after maximum inspiration
• Inspiratory reserve volume + tidal volume + expiratory reserve volume

Question 14

Define total lung capacity

Answer 14

• Volume of air contained in lungs at end of maximal inspiration
• Tidal volume + inspiratory reserve volume + expiratory reserve volume + residual volume

Question 15

Define FEV1

Answer 15

• Forced expiratory volume in 1 second
• Maximum volume of air that can be forcefully expired within 1 second
• After maximum expiration

Question 16

Define FVC

Answer 16

• Forced vital capacity
• Total amount of air exhaled after maximal inspiration
• During entire test
• Occurs over 6 seconds

Question 17

What does the FEV1:FVC ratio represent?

Answer 17

• Represents proportion of patient’s forced vital capacity that they are able to expire in first second of forced expiration
• If FEV1:FVC <0.7 = obstructive pattern

Question 18

What can spirometry can generate graphical representations of?

Answer 18

• Volume of air moved as a function of time - volume-time plot
• Rate of airflow as a function of volume of air in lungs - flow-volume loop

Question 19

What does a volume-time plot show?

Answer 19

• Shows FEV1 graphically
• FVC graphically
• Y axis shows volume of air expired
• X axis shows time

Question 20

What does flow volume loop show?

Answer 20

• Volume of air present in lungs at transition of maximum inspiration to expiration = Total lung capacity
• Volume of air present in lungs at transition of expiration to inspiration is residual volume

Question 21

What is seen in spirometry of a patient with an obstructive lung disease?

Answer 21

• FEV1 decreased
• Size of decrease indicates severity

Question 22

What does spirometry in patients with COPD and asthma show?

Answer 22

• In COPD, FVC is initially normal but decreases in severe disease
• Asthma, FVC is typically decreased due to small airways closing prematurely
• Key diagnostic finding = FEV1:FVC <0.7

Question 23

What happens to total lung capacity and functional residual capacity if there is small airways collapse?

Answer 23

• Air trapping occurs
• Total lung capacity and functional residual capacity are increased
• Due to increased residual volume

Question 24

How do we differentiate between asthma and COPD on spirometry?

Answer 24

• Should see improvement in FEV1 of 12% or more between attacks
• Airways obstruction is reversible

Question 25

Is COPD reversible?

Answer 25

- Degree of reversible airways obstruction - Some patients may respond to inhalers

Question 26

What is seen on a volume-time plot and flow volume loop in obstructive lung disease?

Answer 26

- COPD and asthma are obstructive lung diseases - Reduced FEV1 - Indent in line representing expiration (should be straight)

Question 27

What is FEV1 like in restrictive lung diseases?

Answer 27

- May be normal or decreased - Decrease is proportionate to FVC

Question 28

What is FVC like in restrictive lung disease?

Answer 28

- Decreased

Question 29

What are FRC and TLC like in restrictive lung diseases?

Answer 29

- Always decreased

Question 30

What does a volume-time plot show in restrictive lung disease?

Answer 30

- Low volumes - Rate of air flow is typically normal

Question 31

What will a flow-volume loop show in restrictive lung disease?

Answer 31

- Similar shape to normal - Smaller volumes at all points

Question 32

Give examples of restrictive lung diseases?

Answer 32

- Interstitial lung disease - Myasthenia gravis

Question 33

What do diffusing capacity for carbon monoxide tests determine?

Answer 33

- How much oxygen travels from alveoli of lungs to bloodstream by measuring CO diffusion - Provides information on alveolar-capillary membrane

Question 34

What decreases DLCO?

Answer 34

- Emphysema decreases surface area of alveoli - Alveolar inflammation increases thickness of alveolar membrane - Pulmonary fibrosis increases thickness of alveolar - Would expect to see abnormal X-ray or spirometry

Question 35

What does abnormal DLCO with normal chest X-ray and spirometry suggest?

Answer 35

- Problem with vascular part of membrane - Suggests idiopathic pulmonary hypertension or chronic thrombo-embolic disease of lung

Question 36

How do you differentiate different restrictive lung diseases?

Answer 36

- Parenchymal lung diseases will have a restrictive patter and abnormal DLCO - Restrictive lung diseases related to abnormalities of chest wall (kyphoscoliosis) have normal DLCO - Restrictive lung disease related to neuromuscular disease - e.g. myasthenia gravis - have normal DLCO

Question 37

What is the FEV1:FVC ratio in obstructive disease like?

Answer 37

- Decreased - FEV1 is normal or decreased - FVC is normal or decreased

Question 38

What is the FEV1:FVC ratio in restrictive disease like?

Answer 38

- Normal or increased - FEV1 is normal or decreased - FVC is decreased