1. What is Function Residual Capacity?

Function Residual Capacity (FRC) is the amount of air remaining in the lungs at the end of a normal exhalation. It represents the sum of Residual Volume (RV) and Expiratory Reserve Volume (ERV), providing important information about lung function and respiratory health.

2. How Does the Calculator Work?

The calculator uses the FRC formula:

Where:

• \( FRC \) — Function Residual Capacity (m³)
• \( RV \) — Residual Volume of Lung (m³)
• \( ERV \) — Expiratory Reserve Volume (m³)

Explanation: The equation calculates the total volume of air that remains in the lungs after a normal expiration, combining the air that cannot be voluntarily expelled (RV) with the air that can be expelled with maximum effort (ERV).

3. Importance of FRC Calculation

Details: Accurate FRC measurement is crucial for assessing lung function, diagnosing respiratory disorders, monitoring disease progression, and evaluating the effectiveness of respiratory treatments. It helps identify conditions such as obstructive and restrictive lung diseases.

4. Using the Calculator

Tips: Enter Residual Volume (RV) and Expiratory Reserve Volume (ERV) in cubic meters. Both values must be valid (≥0). Normal adult RV values average around 0.0012 m³ (1200 ml) and ERV values range from 0.0007-0.0012 m³ (700-1200 ml).

5. Frequently Asked Questions (FAQ)

Q1: What is the clinical significance of FRC?
A: FRC helps maintain alveolar stability, prevents lung collapse, and ensures adequate gas exchange between breaths. Abnormal FRC values can indicate various respiratory conditions.

Q2: What are normal FRC values?
A: Normal FRC values for adults typically range between 0.0019-0.0024 m³ (1900-2400 ml), though values vary based on age, gender, height, and body position.

Q3: How is FRC measured clinically?
A: FRC can be measured using techniques such as helium dilution, nitrogen washout, or body plethysmography, which are more accurate than mathematical calculations alone.

Q4: What factors affect FRC?
A: FRC is influenced by age, gender, body position, pregnancy, respiratory diseases, and certain medical conditions that affect lung elasticity and chest wall compliance.

Q5: When should FRC be evaluated?
A: FRC assessment is important when evaluating patients with suspected respiratory disorders, monitoring chronic lung diseases, or assessing preoperative pulmonary risk.