Which term describes the air that does not participate in gas exchange?

Which term describes the air that does not participate in gas exchange?

• A. Alveolar dead space
• B. Physiologic dead space
• C. Anatomic Deadspace
• D. Total dead space

Answer: (C)

Dead space is the portion of each breath that does not participate in gas exchange. The air in the conducting airways—the trachea and bronchi—never reaches the alveoli for gas exchange, so it’s considered dead space. This specific region is called anatomic dead space. Air in alveoli that are ventilated but not perfused is alveolar dead space, and when you combine that with the anatomic portion you get physiologic dead space. Some texts also refer to total dead space as the physiologic dead space, which is the sum of the anatomic and alveolar components. So the term that describes the air not participating in gas exchange in the conducting airways is anatomic dead space. In a typical adult, this is about 150 mL.

Dead space is the portion of each breath that does not participate in gas exchange. The air in the conducting airways—the trachea and bronchi—never reaches the alveoli for gas exchange, so it’s considered dead space. This specific region is called anatomic dead space.

Air in alveoli that are ventilated but not perfused is alveolar dead space, and when you combine that with the anatomic portion you get physiologic dead space. Some texts also refer to total dead space as the physiologic dead space, which is the sum of the anatomic and alveolar components.

So the term that describes the air not participating in gas exchange in the conducting airways is anatomic dead space. In a typical adult, this is about 150 mL.