1. What is Predicted FVC?

Predicted Forced Vital Capacity (FVC) is an estimated value of the maximum amount of air a person can forcibly exhale after taking the deepest breath possible. It is calculated based on demographic factors like height and age to establish expected normal values for pulmonary function testing.

2. How Does the Calculator Work?

The calculator uses the standard predicted FVC equation:

Where:

• \( height \) — Height in centimeters (cm)
• \( age \) — Age in years
• \( coeff \) — Standard coefficients (typically 0.052 for height, 0.022 for age)

Explanation: The equation accounts for the positive correlation between lung capacity and height, and the negative correlation with age due to natural lung function decline.

3. Importance of Predicted FVC Calculation

Details: Calculating predicted FVC is essential for interpreting pulmonary function tests. It helps determine if a patient's actual FVC measurement is within normal limits or indicates potential respiratory conditions such as restrictive lung diseases.

4. Using the Calculator

Tips: Enter height in centimeters and age in years. All values must be valid (height > 0, age between 1-120). The calculator will provide the predicted FVC in liters based on standard coefficients.

5. Frequently Asked Questions (FAQ)

Q1: Why is height used in FVC prediction?
A: Height correlates strongly with lung size and capacity. Taller individuals typically have larger lung volumes and higher FVC values.

Q2: Why does predicted FVC decrease with age?
A: Lung elasticity decreases and chest wall compliance changes with age, leading to reduced lung volumes and flow rates over time.

Q3: Are there different equations for different populations?
A: Yes, different prediction equations exist for various ethnic groups, genders, and geographic populations to account for physiological differences.

Q4: What is a normal FVC percentage?
A: Typically, 80-120% of predicted value is considered normal. Values below 80% may indicate restrictive lung disease.

Q5: When should FVC testing be performed?
A: FVC testing is indicated for evaluating respiratory symptoms, monitoring lung diseases, pre-operative assessment, and occupational health screening.