American EMT Academy Week III Practice Test

When arterial carbon dioxide rises above normal:

The brain stem inhibits respirations. Respirations increase in rate and depth. Exhalation lasts longer than inhalation. Respirations decrease in rate and depth.

Correct Answer:

Respirations decrease in rate and depth.

Explanation:

When arterial carbon dioxide rises, the body’s drive to breathe increases. CO2 crosses into the cerebrospinal fluid and lowers its pH, which stimulates central chemoreceptors in the brainstem. This signals the respiratory muscles to elevate both the rate and the depth of breathing, so more CO2 is expelled. In other words, the normal response to hypercapnia is faster, deeper breaths to blow off the excess gas. The other descriptions don’t fit this automatic ventilatory drive: simply inhibiting breathing or slowing it down would worsen CO2 buildup, and exhalation duration isn’t the direct mechanism by which the body responds to increased CO2.

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