A reduction in respiratory rate would lead to an accumulation of _____ in the blood, resulting in a corresponding increase in _____. What is the most likely condition to induce a decrease in respiratory rate?

A reduction in respiratory rate leads to decreased gas exchange in the lungs, meaning that carbon dioxide (CO2) is not removed from the blood as efficiently. The accumulation of CO2 in the bloodstream results in a shift in pH balance, as CO2 is converted into carbonic acid, which dissociates into bicarbonate and hydrogen ions (H+). Therefore, an increase in H+ ions occurs as a direct result of this CO2 accumulation, leading to a condition known as respiratory acidosis, where the blood becomes more acidic.

In this context, the correct answer highlights the relationship between decreased respiratory rate, CO2 accumulation, and the resulting increase in H+ concentration. Conditions that could induce a decrease in respiratory rate include respiratory depression due to drugs (such as opioids), neurological disorders affecting the brainstem's respiratory centers, or severe illness impairing the body's ability to maintain normal respiratory function.

The understanding of why CO2 and H+ are crucial in this scenario reflects the interplay of respiratory physiology and acid-base balance, critical areas of focus for the MCAT.