Tachypnea can be a normal response to which of the following?

• A. Fever
• B. Fear
• C. Exercise
• D. All of the above

Answer: (D)

Tachypnea is a rapid breathing rate and can be a normal response when the body needs more oxygen or must remove CO2 more quickly. In fever, the body's metabolism speeds up, increasing oxygen use and carbon dioxide production, so breathing rate rises to maintain balance. In fear or anxiety, the fight-or-flight response activates the sympathetic system, increasing ventilatory drive and resulting in faster breathing. With exercise, the muscles demand more oxygen and produce more CO2, so ventilation ramps up to meet that demand. Since all three situations can trigger a normal, adaptive increase in breathing rate, the best answer is that all of the above can cause tachypnea as a normal response.