FEV1/FVC Ratio
Primary spirometry metric for airflow obstruction. <LLN suggests obstructive; normal ratio + low FVC suggests restrictive.
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<70% Obstructive Normal ratio + low FVC Restrictive GOLD 1-4 staging
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Why: Distinguishes obstructive (COPD, asthma) from restrictive (fibrosis) lung disease.
How: Enter FEV1, FVC, demographics. Ratio and % predicted determine pattern and GOLD stage.
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Normal Spirometry (35 years)
Healthy adult with normal pulmonary function testing
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Mild COPD - GOLD 1 (58 years)
Former smoker with mild airflow obstruction, minimal symptoms
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Moderate COPD - GOLD 2 (65 years)
Active smoker with progressive dyspnea and chronic cough
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Severe COPD - GOLD 3 (70 years)
Long-term smoker with severe limitation, frequent exacerbations
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Asthma - Reversible Obstruction (28 years)
Young adult with asthma showing significant bronchodilator response
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Restrictive Pattern - ILD (55 years)
Patient with interstitial lung disease showing restrictive pattern
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Enter Spirometry Values
Spirometry Results
Patient Demographics
Clinical Information
For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
🏥 Health Facts
LLN more accurate than fixed 70%
— Pulmonary
Post-bronchodilator for GOLD
— COPD
What is the FEV1/FVC Ratio?
The FEV1/FVC ratio is the most important parameter in spirometry for detecting airflow obstruction. FEV1 (Forced Expiratory Volume in 1 second) represents how much air can be forcefully exhaled in one second, while FVC (Forced Vital Capacity) is the total amount of air that can be forcefully exhaled. The ratio between these values helps distinguish between obstructive and restrictive lung diseases.
Obstructive Pattern
FEV1/FVC < LLN (or <70%): Indicates airflow obstruction seen in COPD, asthma, bronchiectasis.
- COPD
- Asthma
- Chronic bronchitis
Restrictive Pattern
Normal/High ratio with low FVC: Suggests restriction - reduced lung volumes.
- Pulmonary fibrosis
- Chest wall disease
- Neuromuscular disease
GOLD Classification
For obstructive disease, FEV1% predicted determines severity staging.
- GOLD 1: ≥80%
- GOLD 2: 50-79%
- GOLD 3: 30-49%
- GOLD 4: <30%
How to Interpret Spirometry Results
Interpretation Algorithm
Step 1: Check FEV1/FVC Ratio
If FEV1/FVC < LLN (or <70%): OBSTRUCTIVE pattern
Step 2: Assess FVC
If ratio normal but FVC <80%: Possible RESTRICTIVE pattern (confirm with TLC)
Step 3: Grade Severity
Use FEV1% predicted to determine GOLD stage for obstructive disease
When to Use This Calculator
COPD Diagnosis
Confirm airflow obstruction in smokers or those with chronic respiratory symptoms.
Asthma Assessment
Evaluate for reversible airway obstruction with pre/post bronchodilator testing.
Disease Monitoring
Track progression and treatment response in known lung disease.
Clinical Pearls for FEV1/FVC Interpretation
- 💡FEV1/FVC ratio below LLN (lower limit of normal) is more specific than fixed 0.70 cutoff
- 💡Fixed 0.70 cutoff may overdiagnose COPD in elderly and underdiagnose in younger patients
- 💡Bronchodilator response of >12% AND >200mL suggests reversible obstruction (asthma)
- 💡Reduced FEV1 and FVC with preserved ratio suggests restrictive pattern - confirm with TLC
- 💡Quality criteria: 3 acceptable maneuvers with FEV1 and FVC within 150mL
- 💡Mixed pattern requires both reduced FEV1/FVC AND reduced TLC
- 💡GOLD staging uses post-bronchodilator FEV1 % predicted for COPD severity
Treatment Summary by Pattern
Obstructive Pattern (COPD)
- • Smoking cessation (most important)
- • Bronchodilators (SABA, LABA, LAMA)
- • ICS if frequent exacerbator with eosinophilia
- • Pulmonary rehabilitation
- • Oxygen therapy if indicated
- • Vaccinations (flu, pneumococcal, COVID)
Obstructive Pattern (Asthma)
- • ICS as controller therapy
- • SABA for rescue
- • Step up/down based on control
- • Allergen avoidance
- • Biologics for severe asthma
- • Asthma action plan
Restrictive Pattern
- • Treat underlying cause
- • Pulmonary rehabilitation
- • Oxygen therapy if needed
- • Antifibrotics for IPF
- • Immunosuppression for inflammatory ILD
- • Lung transplant evaluation if severe
Mixed Pattern
- • Address both components
- • Bronchodilators for obstruction
- • Treat underlying restrictive disease
- • Comprehensive pulmonary rehabilitation
- • Multidisciplinary management
When to Refer to Pulmonology
- →Uncertain diagnosis or atypical presentation
- →Severe disease (FEV1 <50% predicted)
- →Rapid decline in lung function
- →Suspected interstitial lung disease
- →Frequent exacerbations despite optimal therapy
- →Consideration for biologics, oxygen, or transplant
- →Need for complete PFT testing (full lung volumes, DLCO)
Spirometry Quick Reference
Normal
FEV1/FVC >0.70
FEV1 >80% predicted
Obstructive
FEV1/FVC <0.70
COPD, Asthma
Restrictive
FEV1/FVC ≥0.70
FVC <80%, confirm with TLC
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