Minute volume is calculated by which formula?

• A. It increases if tidal volume decreases
• B. It decreases if respiratory rate increases while tidal volume remains the same
• C. It increases if tidal volume increases while respiratory rate remains the same
• D. It is unaffected by tidal volume

Answer: (C)

Minute volume is the total air moved in and out of the lungs each minute. It’s found by multiplying the amount of air per breath (tidal volume) by how many breaths you take each minute (respiratory rate). So when tidal volume increases and the rate stays the same, more air is moved per breath, and that directly raises minute volume. For example, with a tidal volume of 500 mL and a rate of 12 breaths per minute, minute volume is 6,000 mL/min. If tidal volume increases to 600 mL at the same rate, minute volume becomes 7,200 mL/min. Conversely, reducing tidal volume would lower minute volume, and increasing the respiratory rate with the same tidal volume would also raise minute volume—so the statement that minute volume is unchanged by tidal volume is incorrect.