If chest barely moves during inhalation and the respiratory rate is normal, which respiratory parameter is most likely decreased?

• A. Tidal volume
• B. Minute volume
• C. Inspiratory Reserve Volume
• D. Expiratory Reserve Volume

Answer: (B)

The situation shows shallow breathing with a normal breathing rate, so the amount of air moved per breath is reduced. Minute volume, which is the total air moved per minute, is the product of tidal volume (air per breath) and respiratory rate. With the rate held steady and tidal volume decreased by the shallow inhalation, the minute volume must drop. That’s why the most likely decreased parameter is minute volume.

Note how the other measures fit: tidal volume itself is decreased because each breath brings in less air, but the question focuses on the per-minute amount of air moved given a normal rate, so minute volume directly reflects the overall ventilation change. Inspiratory and expiratory reserve volumes are about extra air beyond normal tidal breaths, which isn’t directly indicated by shallow, routine inhalation here.