FEV1/FVC Ratio Calculator (Tiffeneau Index)
Health & FitnessCalculate the FEV1/FVC ratio used to assess airflow obstruction on spirometry.
FEV1/FVC Ratio
Tiffeneau index (FEV1/FVC). Educational reference only, not a substitute for clinical judgment.
Interpretation
General interpretation, using a lower threshold for patients over 65. At or above threshold - normal airflow pattern
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Frequently Asked Questions
What does the FEV1/FVC ratio measure?
It measures the proportion of total lung capacity that can be forcefully exhaled in the first second, used to identify airflow obstruction, most commonly associated with COPD or asthma.
What is considered a normal FEV1/FVC ratio?
A ratio above 70% is generally considered normal in most adults, though the threshold is often lowered to 65% for patients over 65 to account for normal age-related lung changes.
Does a low ratio always mean COPD?
A low ratio indicates an obstructive pattern, which is characteristic of COPD but can also occur in asthma and other conditions. A low ratio alone does not distinguish between these causes; the full clinical picture and pattern of FEV1 recovery after bronchodilator matter too.
Is this calculator a substitute for medical advice?
No. This is an educational reference implementation of the standard FEV1/FVC ratio, not a substitute for a physicians clinical assessment or full spirometry interpretation.
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