Pulmonary function tests Flashcards
1
Q
What are pulmonary function tests?
A
- Tests that measure:
- Lung volumes
- Rate of airflow
- Gas exchange
2
Q
What are pulmonary function tests used for?
A
- Diagnose patients with respiratory problems
- Establish severity and progression of lung disease
- Assess treatment response
- Monitor patients on meds with lung toxicity
3
Q
What instruments and methods are used to carry out pulmonary function tests?
A
- Peak flow meter
- Spirometry
- Diffusing capacity for carbon monoxide
- Body plethysmography
4
Q
How is peak expiratory flow measured?
A
- 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
5
Q
What is spirometry used for?
A
- Measures some lung volumes
- Calculates airflow as volumes are measured over time
- Produces graphical representations
6
Q
Define tidal volume
A
- Amount of air moving in and out of lungs at rest
7
Q
Define inspiratory reserve volume
A
- Additional amount of air can be inhaled after normal inspiration
- I.e. how much more air we can breathe in above tidal volume
8
Q
Define expiratory reserve volume
A
- Additional amount of air can be exhaled after normal expiration
- I.e. how much more air we can breathe out above tidal volume
9
Q
Define residual volume
A
- Amount of air remaining in lungs after maximal forceful expiration
10
Q
Define inspiratory capacity
A
- Total volume of air that can be inspired following a normal expiration (tidal volume + inspiratory reserve volume)
11
Q
Define functional residual capacity
A
- Volume of air present in lungs at end of passive expiration
- Expiratory reserve volume + residual volume
12
Q
Define total lung capacity
A
- Volume of air contained in lungs at end of a maximal inspiration
- Tidal volume + inspiratory reserve volume + expiratory reserve volume + residual volume
13
Q
Define vital capacity
A
- Volume of air exhaled after maximum inspiration
- Inspiratory reserve volume + tidal volume + expiratory reserve volume
14
Q
Define total lung capacity
A
- Volume of air contained in lungs at end of maximal inspiration
- Tidal volume + inspiratory reserve volume + expiratory reserve volume + residual volume
15
Q
Define FEV1
A
- Forced expiratory volume in 1 second
- Maximum volume of air that can be forcefully expired within 1 second
- After maximum expiration
16
Q
Define FVC
A
- Forced vital capacity
- Total amount of air exhaled after maximal inspiration
- During entire test
- Occurs over 6 seconds
17
Q
What does the FEV1:FVC ratio represent?
A
- 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
18
Q
What can spirometry can generate graphical representations of?
A
- 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
19
Q
What does a volume-time plot show?
A
- Shows FEV1 graphically
- FVC graphically
- Y axis shows volume of air expired
- X axis shows time
20
Q
What does flow volume loop show?
A
- 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
21
Q
What is seen in spirometry of a patient with an obstructive lung disease?
A
- FEV1 decreased
- Size of decrease indicates severity
22
Q
What does spirometry in patients with COPD and asthma show?
A
- 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
23
Q
What happens to total lung capacity and functional residual capacity if there is small airways collapse?
A
- Air trapping occurs
- Total lung capacity and functional residual capacity are increased
- Due to increased residual volume
24
Q
How do we differentiate between asthma and COPD on spirometry?
A
- Should see improvement in FEV1 of 12% or more between attacks
- Airways obstruction is reversible
25
Is COPD reversible?
- Degree of reversible airways obstruction
- Some patients may respond to inhalers
26
What is seen on a volume-time plot and flow volume loop in obstructive lung disease?
- COPD and asthma are obstructive lung diseases
- Reduced FEV1
- Indent in line representing expiration (should be straight)
27
What is FEV1 like in restrictive lung diseases?
- May be normal or decreased
- Decrease is proportionate to FVC
28
What is FVC like in restrictive lung disease?
- Decreased
29
What are FRC and TLC like in restrictive lung diseases?
- Always decreased
30
What does a volume-time plot show in restrictive lung disease?
- Low volumes
- Rate of air flow is typically normal
31
What will a flow-volume loop show in restrictive lung disease?
- Similar shape to normal
- Smaller volumes at all points
32
Give examples of restrictive lung diseases?
- Interstitial lung disease
- Myasthenia gravis
33
What do diffusing capacity for carbon monoxide tests determine?
- How much oxygen travels from alveoli of lungs to bloodstream by measuring CO diffusion
- Provides information on alveolar-capillary membrane
34
What decreases DLCO?
- 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
35
What does abnormal DLCO with normal chest X-ray and spirometry suggest?
- Problem with vascular part of membrane
- Suggests idiopathic pulmonary hypertension or chronic thrombo-embolic disease of lung
36
How do you differentiate different restrictive lung diseases?
- 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
37
What is the FEV1:FVC ratio in obstructive disease like?
- Decreased
- FEV1 is normal or decreased
- FVC is normal or decreased
38
What is the FEV1:FVC ratio in restrictive disease like?
- Normal or increased
- FEV1 is normal or decreased
- FVC is decreased
