1. What is FEV1 % Predicted?

FEV1 % Predicted is a measure used in pulmonary function testing that compares a person's measured FEV1 (Forced Expiratory Volume in 1 second) to the predicted FEV1 value for a healthy person of the same age, height, sex, and ethnicity. It helps assess the severity of lung disease.

2. How Does the Calculator Work?

The calculator uses the FEV1 % Predicted formula:

Where:

• Measured FEV1 — The actual FEV1 measurement from spirometry (L)
• Predicted FEV1 — The expected FEV1 value for a healthy individual (L)

Explanation: This calculation expresses the measured FEV1 as a percentage of what would be expected in a healthy person, providing a standardized way to interpret lung function results.

3. Importance of FEV1 % Predicted

Details: FEV1 % Predicted is crucial for diagnosing and monitoring obstructive lung diseases like asthma and COPD, determining disease severity, assessing treatment response, and evaluating prognosis.

4. Using the Calculator

Tips: Enter both measured and predicted FEV1 values in liters (L). Both values must be positive numbers. The predicted FEV1 is typically calculated using reference equations based on age, height, sex, and ethnicity.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal FEV1 % Predicted value?
A: Typically, values above 80% are considered normal. Values between 70-79% may indicate mild impairment, 60-69% moderate impairment, and below 60% severe impairment.

Q2: How is predicted FEV1 determined?
A: Predicted values are calculated using reference equations that consider age, height, sex, and sometimes ethnicity. Different equations exist for different populations.

Q3: Why use % predicted instead of absolute values?
A: Percentage predicted normalizes results for individual characteristics, allowing for better comparison across different patients and tracking changes over time.

Q4: Can FEV1 % Predicted be used for diagnosis?
A: While it's an important measure, diagnosis should be based on comprehensive pulmonary function testing and clinical evaluation, not just this single value.

Q5: How often should FEV1 be measured?
A: Frequency depends on the clinical situation. For stable COPD or asthma, it might be measured annually. For acute exacerbations or treatment changes, it may be measured more frequently.