The volume of air in the dead space fo human lungs is normally

Options

A. 230 mL
B. 210 mL
C. 190 mL
D. 159mL

Answer

To determine the volume of air in the dead space of human lungs, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Dead Space**:
- The dead space in the lungs refers to areas where air is present but no gas exchange occurs. This includes parts of the respiratory system such as the trachea and bronchi.

2. **Identifying Tidal Volume**:
- Tidal volume is the amount of air that is inhaled or exhaled during normal breathing. A portion of this tidal volume does not participate in gas exchange.

3. **Percentage of Dead Space**:
- It is commonly understood that approximately 30% of the tidal volume is considered dead space.

4. **Calculating Dead Space Volume**:
- The average tidal volume in adults is about 500 ml. Therefore, to find the dead space volume, we can calculate 30% of 500 ml:
\[ \text{Dead Space Volume} = 0.30 \times 500 \text{ ml} = 150 \text{ ml} \]

5. **Considering Variability**:
- While the calculated value is 150 ml, it is important to note that the dead space volume can vary slightly among individuals. The typical range is often cited as being between 158 ml to 160 ml.

6. **Selecting the Correct Option**:
- Among the provided options (230 ml, 210 ml, 190 ml, and 159 ml), the closest and most accurate estimate for the volume of air in the dead space of human lungs is **159 ml**.

### Final Answer:
The volume of air in the dead space of human lungs is normally **159 ml**.

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