In conditions of hypercapnia, what is the expected impact on the respiratory drive?

• A. Decreased respiratory effort
• B. Increased respiratory effort
• C. No change in respiratory effort
• D. Unpredictable respiratory effort

Answer: (B)

In conditions of hypercapnia, which is characterized by an elevated level of carbon dioxide in the blood, the expected impact on the respiratory drive is an increase in respiratory effort. The body senses rising carbon dioxide levels through chemoreceptors located in the brainstem and peripheral tissues.

These chemoreceptors are highly sensitive to changes in carbon dioxide and, to a lesser extent, oxygen levels. When hypercapnia occurs, the increased concentration of carbon dioxide leads to decreased pH (acidosis) in the cerebrospinal fluid, stimulating the brain's respiratory centers to enhance the rate and depth of breathing. This response aims to expel excess carbon dioxide and restore normal levels in the bloodstream, thus increasing respiratory effort to improve ventilation.

In contrast, decreased respiratory effort would not help alleviate hypercapnia, nor would there be no change or unpredictable variations in effort, as the body typically mounts a protective response to such an acute change in gas levels. Therefore, the increase in respiratory effort is a direct physiological response to maintain homeostasis in the presence of excess carbon dioxide.