Pulmonary Tests Flashcards
How do you distinguish between obstructive vs restrictive lung disorders?
Volume time curve
- restrictive —> shorter
- FEV1 same, FVC low —> high FEV1/FVC
- obstructive —> short and long
- FEV1 low, FVC low —> low FEV1/FVC
What are the 2 types of respiratory disorders?
- Obstructive —> obstructed airflow
- airway diseases eg. COPD
—> see via chest X-ray - Restrictive —> restrict lung filling
- extra-airway diseases eg. obesity
How do you interpret volume-time spirometry?
FVC —> highest value
FEV1 —> volume at 1 second
PEFR —> gradient of line portion
How do you interpret flow volume loop spirometry?
FVC —> width of loop
FEV1 —> separate marker
PEFR —> highest point
How does a peak flow meter work?
Most forceful exhalation —> PEFR
- compare to chart
What is FVC, FEV1 and PEFR?
FVC = Forced Vital Capacity
- max exhalation volume
FEV1 = Forced Expiratory Volume 1
- max expired volume in 1 second
PEFR = Peak Expiratory Flow Rate
- max rate of exhalation
How is FEV1/FVC used in diagnosis?
Normal —> 0.75-0.85
Restrictive —> high (>0.85)
Obstructive —> low (<0.75)
What is the use of volume time curves?
Distinguish between restrictive vs obstructive lung diseases
- Restrictive —> shorter
- FEV1 same, FVC low —> high FEV1/FVC
- Obstructive —> short and long
- FEV1 low, FVC low —> low FEV1/FVC
What are flow-volume loops?
Graph of lung volume against flow rate
- expiration —> up
inspiration —> down
1. Tidal breath —> find TV
2. Inhale to TLC —> find IRV
3. Fastest exhale —> find PEF
4. Exhale till only RV left —> see FEV1
—> find ERV
5. Inhale back to TLC —> find VC
How do restrictive vs obstructive diseases affect flow-volume loops?
Restrictive —> narrower (dec FVC)
Obstructive —> narrower (dec FVC)
—> coving (dec FEV1)
- extrathoracic —> bottom blunted
- rest normal
intrathoracic —> top blunted
- rest normal
fixed obstruction —> both blunted
- rest normal
