Alveolar ventilation is calculated as which expression?

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Multiple Choice

Alveolar ventilation is calculated as which expression?

Alveolar ventilation is the amount of air per minute that actually reaches the gas-exchange surfaces. Each breath delivers only the portion of tidal volume that makes it to the alveoli, which is tidal volume minus dead space. Multiply that effective volume per breath by the number of breaths you take each minute to get the per-minute alveolar ventilation. That’s why the correct expression is (tidal volume minus dead space) × respiratory rate. The other forms don’t fit because they either multiply by dead space, divide by rate, or subtract dead space after a different operation, which doesn’t reflect how much air actually reaches the alveoli each minute. Example: with a tidal volume of 500 mL, dead space 150 mL, and a rate of 12 breaths per minute, alveolar ventilation = (500 − 150) × 12 = 4,200 mL/min (about 4.2 L/min).

Alveolar ventilation is the amount of air per minute that actually reaches the gas-exchange surfaces. Each breath delivers only the portion of tidal volume that makes it to the alveoli, which is tidal volume minus dead space. Multiply that effective volume per breath by the number of breaths you take each minute to get the per-minute alveolar ventilation. That’s why the correct expression is (tidal volume minus dead space) × respiratory rate.

The other forms don’t fit because they either multiply by dead space, divide by rate, or subtract dead space after a different operation, which doesn’t reflect how much air actually reaches the alveoli each minute. Example: with a tidal volume of 500 mL, dead space 150 mL, and a rate of 12 breaths per minute, alveolar ventilation = (500 − 150) × 12 = 4,200 mL/min (about 4.2 L/min).

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