If a person breathes with maximal effort but with his nose and mouth closed, the alveolar pressure can be decreased to as low as

Options

A. `-80 mm Hg`
B. `+10 mm Hg`
C. `-180 mm Hg`
D. `-250 mm Hg`

Explanation

To solve the question regarding the alveolar pressure when a person breathes with maximal effort but with their nose and mouth closed, follow these steps:

### Step-by-Step Solution:

1. **Understanding Alveolar Pressure**: Alveolar pressure is the pressure within the alveoli of the lungs. It can change during the breathing process based on the volume of air in the lungs and the effort exerted during breathing.

2. **Breathing with Closed Airways**: When a person attempts to breathe with their nose and mouth closed, they cannot take in fresh air. This situation creates a scenario where the pressure in the alveoli can be altered significantly.

3. **Maximal Effort Breathing**: Maximal effort breathing refers to the act of trying to inhale or exhale forcefully. In this case, the person is trying to expand their lungs against a closed airway, which can lead to a decrease in pressure within the alveoli.

4. **Pressure Changes**: Under normal circumstances, the alveolar pressure fluctuates between atmospheric pressure (0 mmHg) and negative pressure during inhalation. However, with maximal effort and closed airways, the pressure can drop significantly.

5. **Identifying the Lowest Pressure**: The question asks for the lowest possible alveolar pressure that can be achieved under these conditions. Based on physiological data, the alveolar pressure can decrease to about -80 mmHg when maximal effort is exerted with closed airways.

6. **Conclusion**: Therefore, the answer to the question is that the alveolar pressure can be decreased to as low as **-80 mmHg**.

### Final Answer:
The alveolar pressure can be decreased to as low as **-80 mmHg**.

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