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
What does this flow volume loop indicate?
Coughing
What does this flow volume loop indicate?
Slow start
What does this flow volume loop indicate?
False start
What does this flow volume loop indicate?
Early termination
What does this flow volume loop indicate?
Variable effort
What does this flow volume loop indicate?
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
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
14 yo boy with severe extensive bronchiectasis
- FVC 85%
- FEV1 42%
- FEV1/FVC 42
- FEF 25-75 13%
- FEF50 15%
- PF 69%
- TLC 122%
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)