Which of the following is NOT listed as a symptom of hypercapnia?

• A. Increased rate and depth of breathing
• B. Shortness of breath with rapid breathing
• C. Headache
• D. Dizziness

Answer: (D)

Hypercapnia, or elevated CO2 in the blood, triggers signs that reflect the body’s efforts to ventilate more and the effects of CO2 on the brain. When CO2 rises, chemoreceptors stimulate the respiratory drive, so you commonly see an increased rate and depth of breathing as the body tries to blow off the excess gas. That increased ventilation is tied to the sensation of shortness of breath with rapid breathing, often described as dyspnea with tachypnea. The brain’s blood vessels dilate in response to higher CO2, which frequently leads to headaches. Among the listed signs, dizziness is not a typical or consistently listed symptom of hypercapnia, so it doesn’t fit as a standard sign and is less specific to CO2 retention than the others.