What effect does a small increase in CO2 concentration in inspired air have on ventilation?

• A. Increase ventilation
• B. Decrease ventilation
• C. No effect on ventilation
• D. Cause shortness of breath

Answer: (A)

A small increase in carbon dioxide (CO2) concentration in the inspired air leads to an increase in ventilation. This occurs because the respiratory center in the brain, particularly the medulla oblongata, is highly sensitive to changes in CO2 levels. When CO2 concentrations rise, it indicates that the body is producing more metabolic waste, which can lead to acidemia if not removed.

The body responds to elevated CO2 levels by increasing the rate and depth of breathing. This physiological response, known as hypercapnic response, helps to expel the excess CO2, thereby restoring homeostasis. Increased ventilation effectively lowers the amount of CO2 in the blood, consequently helping to maintain the acid-base balance.

In contrast, options indicating a decrease in ventilation or no effect do not align with the body's intrinsic response mechanisms to elevated CO2 levels. Therefore, the appropriate adaptive response to a small increase in CO2 concentration is indeed an increase in ventilation to efficiently clear CO2 and support normal physiological function.