10c.10 Dead Space

Question 1

What is dead space in the respiratory system?

Answer 1

Air that is inhaled but does not participate in gas exchange.

Question 2

Why is air in dead space not used for gas exchange?

Answer 2

It either does not reach the alveoli or reaches alveoli that lack blood supply.

Question 3

What are the two main types of dead space?

Answer 3

Anatomical dead space and physiologic dead space.

Question 4

What is anatomical dead space?

Answer 4

Air in the conducting airways that never reaches the alveoli.

Question 5

What parts of the respiratory system make up anatomical dead space?

Answer 5

Nose, pharynx, larynx, trachea, bronchi, and bronchioles.

Question 6

Can anatomical dead space change?

Answer 6

No, it is fixed and based on airway anatomy.

Question 7

Approximately how much air is in anatomical dead space in a healthy adult?

Answer 7

About 150 mL.

Question 8

What is physiologic dead space?

Answer 8

Alveoli that receive air but have no blood flow for gas exchange.

Question 9

When does physiologic dead space increase?

Answer 9

When alveoli are ventilated but not perfused (e.g., in pulmonary embolism).

Question 10

What causes physiologic dead space?

Answer 10

Pulmonary embolism, vascular obstruction, or poor perfusion.

Question 11

What is the difference between anatomical and physiologic dead space?

Answer 11

Anatomical is structural (airways); physiologic depends on blood flow to alveoli.

Question 12

What happens to alveolar ventilation during rapid, shallow breathing (tachypnea)?

Answer 12

It decreases because most air stays in dead space and does not reach alveoli.

Question 13

Why is shallow breathing inefficient for gas exchange?

Answer 13

It moves air mainly in and out of dead space rather than alveoli.

Question 14

What term describes air movement that does not contribute to gas exchange?

Answer 14

Dead space ventilation.

Question 15

What happens to oxygen and carbon dioxide exchange during dead space ventilation?

Answer 15

Minimal oxygen enters and minimal carbon dioxide is removed.

Question 16

How does dead space relate to ventilation–perfusion (V/Q) mismatch?

Answer 16

Increased physiologic dead space is a form of V/Q mismatch where ventilation exceeds perfusion.

Question 17

What are common conditions that increase physiologic dead space?

Answer 17

Pulmonary embolism, COPD, or alveolar overdistension from mechanical ventilation.

Question 18

What is the effect of increased dead space on gas exchange?

Answer 18

Decreased oxygen delivery and impaired CO₂ elimination.

Question 19

How can efficient gas exchange be maintained?

Answer 19

By ensuring deep breaths that move air beyond dead space into alveoli.

Question 20

What is the key difference between dead space and alveolar ventilation?

Answer 20

Dead space = air not exchanging gases; alveolar ventilation = air reaching alveoli for exchange.