If a patient with a chest injury is only able to inhale small amounts of air per breath, he or she

• A. will eliminate more carbon dioxide than if breathing deeply.
• B. must increase his or her respiratory rate to maintain adequate minute volume.
• C. often breathes at a slower rate because of lung damage caused by the injury.
• D. will maintain adequate minute volume if his or her respiratory rate stays the same.

Answer: (B)

Minute volume is the amount of air moved in and out of the lungs each minute, and it’s determined by multiplying tidal volume (air per breath) by respiratory rate (breaths per minute). If a chest injury limits how much air can be inhaled per breath, tidal volume drops. To keep minute volume from falling, the patient must increase the breathing rate. If the rate stays the same, minute volume decreases, reducing ventilation and gas exchange. Deep breaths won’t compensate when the inhale volume per breath is limited, and slower or unchanged rates won’t maintain adequate minute volume.