Using a spirometer: with patient standing or sitting upright ask them to blow as hard, fast and long as they can.
Terminology:
- FVC = forced vital capacity – indicator of lung volume
- FEV1 = forced expiratory volume in 1 second
- FEV1/FVC ratio = forced expiratory ratio; 0.75 to 0.8 in normal individuals
Patterns:
- Obstructive
- FEV1 is more reduced than FVC
- Overall FEV1/FVC ratio is <75%
- Causes: CABCAB
- COPD
- Asthma
- Bronchiectasis
- Cystic Fibrosis
- Alpha 1 antitrypsin deficiency
- Bronchiolitis
- Restrictive
- Reduced FVC
- FEV1/FVC is normal or increased
- Causes:
- Lung fibrosis
- Obesity
- Neuromuscular disorders
- Sarcoidosis
Severity of any spirometric abnormality based on FEV1:
- Mild >70% predicted
- Moderate 60-69% predicted
- Moderately severe 50-59% predicted
- Severe 35-49% predicted
- Very severe <35% predicted
Small print gem: spirometry should be avoided within a month of an MI.
References:
