Which one of the following is incorrect?

Options

A. Expiratory capacity = ERV + TV
B. Vital capacity = TLC - RV
C. Inspiratory capacity = TV + IRV
D. Total lung capacity = IRV + ERV + RV

Answer

To solve the question "Which one of the following is incorrect?" regarding the definitions and relationships of various lung volumes and capacities, we can analyze each option provided in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Expiratory Capacity (EC)**:
- Expiratory Capacity (EC) is defined as the sum of Tidal Volume (TV) and Expiratory Reserve Volume (ERV).
- Formula: EC = TV + ERV
- According to the transcript, this statement is correct.

2. **Understanding Vital Capacity (VC)**:
- Vital Capacity (VC) is defined as the maximum amount of air that can be exhaled after a maximum inhalation. It can also be calculated by subtracting Residual Volume (RV) from Total Lung Capacity (TLC).
- Formula: VC = TLC - RV
- The transcript confirms that this statement is correct.

3. **Understanding Inspiratory Capacity (IC)**:
- Inspiratory Capacity (IC) is the maximum amount of air that can be inhaled after a normal expiration. It is the sum of Tidal Volume (TV) and Inspiratory Reserve Volume (IRV).
- Formula: IC = TV + IRV
- The transcript indicates that this statement is correct.

4. **Understanding Total Lung Capacity (TLC)**:
- Total Lung Capacity (TLC) is the total volume of the lungs after a maximum inhalation. It is the sum of Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), Residual Volume (RV), and Tidal Volume (TV).
- Formula: TLC = IRV + ERV + RV + TV
- The transcript states that the given option for TLC is incorrect because it does not include Tidal Volume (TV) in the equation provided.

### Conclusion:
The incorrect statement among the options provided is the one regarding Total Lung Capacity (TLC), which is missing Tidal Volume (TV) in its definition.

**Correct Answer**: The incorrect option is the one stating that Total Lung Capacity equals IRV + ERV + RV (it should also include TV).

---