If a person is unable to breathe on his own due to some medical illness, an iron lung may be employed to take over the role of the diaphragm and the intercostal muscles. The person is placed in a cylindrical chamber called iron lung while his head remains outside the cylinder. An airtight seal is placed around his neck. Changes in the air pressure within the iron lung allow the flow of air into and out of his lungs.
Which of the following statements about the iron lung is correct?

Options

A. Breathing with an iron lung is still possible if the patient's trachea is completely blocked.
B. During exhalation, the iron lung causes the patient's lungs to expand.
C. During inhalation, the pressure in the patient's lungs is increased.
D. Inhalation and exhalation is possible even if the patient's lung is punctured.

Explanation

To solve the question regarding the iron lung and its functionality, we need to analyze the statements provided and determine which one is correct based on the information given in the video transcript.

### Step-by-Step Solution:

1. **Understand the Function of the Iron Lung**:
- The iron lung is designed to assist individuals who cannot breathe on their own due to medical conditions. It mimics the actions of the diaphragm and intercostal muscles by changing air pressure.

2. **Evaluate the Statements**:
- **Statement 1**: "Breathing with iron lung is still possible if the patient's trachea is completely blocked."
- This statement is incorrect. The trachea must be open for air to flow into the lungs. If it is blocked, breathing cannot occur.

- **Statement 2**: "During exhalation, the iron lung causes the patient's lung to expand."
- This statement is also incorrect. During exhalation, the lungs actually contract, not expand. The iron lung creates a pressure change that helps facilitate this process.

- **Statement 3**: "During inhalation, the pressure in the patient's lungs is increased."
- This statement is incorrect. Inhalation occurs when the pressure in the lungs decreases, allowing air to flow in.

- **Statement 4**: "Inhalation and exhalation is possible even if the patient's lung is punctured."
- This statement is correct. Even if the lung is punctured, the iron lung can still facilitate breathing by controlling the air pressure, allowing air to flow in and out.

3. **Conclusion**:
- Based on the evaluation of the statements, the correct answer is **Statement 4**: Inhalation and exhalation is possible even if the patient's lung is punctured.