Which statement best defines alveolar minute volume?

• A. The volume of air moved through the lungs in 1 minute minus the dead space, calculated by multiplying tidal volume (minus dead space) and respiratory rate
• B. The total air moved into the lungs per minute
• C. The volume of air reaching the alveoli per minute
• D. The air remaining in the conducting airways after exhalation

Answer: (A)

The main idea here is alveolar ventilation—the portion of each breath that actually reaches the gas-exchange surfaces in the alveoli per minute. Alveolar minute volume is calculated by taking the air you move with each breath that can reach the alveoli (tidal volume minus dead space) and multiplying it by how many breaths you take each minute. Put simply, VA = (tidal volume − dead space) × respiratory rate. This reflects the real air available for gas exchange per minute.

For example, if tidal volume is 500 mL, dead space is 150 mL, and the rate is 12 breaths per minute, alveolar ventilation is (500 − 150) × 12 = 3600 mL per minute. The total air moved per minute (minute ventilation) would be 500 × 12 = 6000 mL, which includes air that remains in the conducting airways and doesn’t reach the alveoli.

The air remaining in the conducting airways after exhalation describes dead space, not alveolar ventilation. And while the phrase “volume of air reaching the alveoli per minute” captures the same idea in common language, the explicit subtraction of dead space in the formula makes the statement about alveolar minute volume precise and widely accepted.