Question

Alice realizes she's late to class and jogs there, panting at 40 mL/minute. If her alveolar ventilation is 20 L/minute during her run, and she has a 100 mL dead space in her respiratory system, what is her tidal volume during exercise? Express your results in mL/breath.

Answer 1

Tidal volume means volume of air inhaled during normal breath.

Alveolar ventilation can be calculated using below formula, but we have all values except tidal volume. So let’s substitute the values to get tidal volume.

Alveolar Ventilation = (Respiratory Rate) × (Tidal Volume-Dead Space Volume)

As per the given description Alveolar Ventilation = 20 L/min = 20000 mL/min

Respiratory Rate (breathing rate) = 40 mL/min

Dead Space Volume = 100 mL

Substitute these values in above formula

20000 = (40) × (Tidal Volume - 100)

20000/40 = Tidal Volume – 100

500 = Tidal Volume – 100

Therefore, Tidal volume = 500 + 100 = 600 mL/breath