🫁FEV1 Spirometry Calculator
FEV1 (Forced Expiratory Volume in 1 second) is the volume of air expelled in the first second of a forced breath out. FEV1/FVC ratio (Tiffeneau index) < 0.70 is diagnostic of obstructive lung disease. FEV1 < 80% predicted indicates airflow limitation.
- 1FEV1/FVC < 0.70 → obstruction (COPD, asthma)
- 2FEV1 ≥ 80% predicted = normal
- 3FEV1 70–79% = mild obstruction
- 4FEV1 50–69% = moderate · FEV1 < 50% = severe
FEV1=2.5L · FVC=3.2L · predicted FEV1=3.5L=FEV1/FVC=0.78 → obstruction · 71% of predicted → moderateBoth ratio and % predicted needed for staging
| Stage | FEV1 % predicted | Severity |
|---|---|---|
| GOLD 1 | >= 80% | Mild |
| GOLD 2 | 50–79% | Moderate |
| GOLD 3 | 30–49% | Severe |
| GOLD 4 | < 30% | Very severe |
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Fun Fact
COPD (the leading cause of reduced FEV1) affects over 300 million people worldwide and is the third leading cause of death. Spirometry can detect it years before symptoms appear.
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