Respiratory Flashcards
For results to be consistent in spirometry, FVC and FEV1 have to be within what percentage?
5%
What is a normal FEV1?
>80%
What is a normal FEV1/FVC ratio?
100%
What is FEF25-75%?
Mean expiratory flow over the mid 50% of expiration
Describe a normal flow volume loop.
Top loop is expiration
bottom loop inspiration
PEF = airflow in large airways
FEF25-75% = small airways, effort independent
FEV1 = middle airways
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What does this flow volume loop indicate?
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Coughing
What does this flow volume loop indicate?
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Slow start
What does this flow volume loop indicate?
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False start
What does this flow volume loop indicate?
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Early termination
What does this flow volume loop indicate?
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Variable effort
What does this flow volume loop indicate?
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Not at TLC prior to start
What does a reduction in FVC indicate?
- Reduced lung size
- Restrictive lung disease or
- severe air flow limitation.
What does a reduction in FEV1 indicate?
Airflow limitation or severe restrictive process. [earliest change associated with airflow limitation seen in small airways (FEF: 75 then 25-50)]
What do changes in FEV1/FVC ratio indicate?
Proportion of Vital Capacity expired in 1 second.
Normal is 80%
FEV1/FVC ratio is decreased in obstructive lung disease.
If <70%, COPD can be diagnosed.
In restrictive lung disease, both FEV1 and FVC are reduced, therefore FEV1/FVC ratio should be approximately normal or increased.
10 yr old girl with persistant wheeze and cough.
FVC 98%
FEV1 76%
FEV1/FVC 69
FEF 25-75 34%
FEF50 44%
PF 77%
FIF 50% 116
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Inspiratory loop normal
Concave expiratory loop = obstructive.
FVC good
FEV1 reduced
FEV1/FVC reduced
FEF 25-75 reduced
Obstructive picture - asthma
What do you expect to see in an obstructive picture in spirometry?
- Low FEV1
- Low FEF 25-75
- Normal FVC
- FEV1/FVC
- Flow volume loop: Concave
- Normal large airways – can reach PEF
- Airways chockablock – air comes out slower like blowing through a straw
- Bronchodilator responsiveness: >12% increase FEV1
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14 yo boy with severe extensive bronchiectasis
- FVC 85%
- FEV1 42%
- FEV1/FVC 42
- FEF 25-75 13%
- FEF50 15%
- PF 69%
- TLC 122%
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Mod to severe obstructive lung disease
- PEF reduced
- Concave expiratory loop
- FVC almost normal
- FEV1 reduced
- FEV1/FVC reduced
- FEF 25-75 reduced
- TLC high indicating air trapping
(FEV1/FVC ratio is decreased in obstructive lung disease)