Total dead space in healthy individuals –
**Core Concept**
The total dead space in healthy individuals refers to the volume of the respiratory system where gas exchange does not occur. This includes the **anatomical dead space**, which comprises the conducting airways, and the **alveolar dead space**, where blood flow and ventilation do not match.
**Why the Correct Answer is Right**
In healthy individuals, the total dead space is approximately equal to the **tidal volume** minus the **alveolar volume**. The **anatomical dead space** is roughly 150 mL, which corresponds to the volume of the conducting airways.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it underestimates the total dead space.
**Option B:** This option is also incorrect as it overestimates the total dead space.
**Option D:** This option is incorrect because it does not accurately reflect the total dead space in healthy individuals.
**Clinical Pearl / High-Yield Fact**
Remember that **anatomical dead space** increases with lung volume and decreases with lung disease, such as chronic obstructive pulmonary disease (COPD).
**Correct Answer:** B. 150 mL