What is the primary change observed in pH during respiratory acidosis?

• A. Increased pH
• B. Decreased pH
• C. Normal pH
• D. Fluctuating pH

Answer: (B)

In respiratory acidosis, the primary change observed is a decrease in pH. This condition arises when there is an accumulation of carbon dioxide (CO2) in the bloodstream, typically due to inadequate respiratory function, leading to an increased concentration of carbonic acid. This increased carbonic acid lowers the pH of the blood, resulting in acidosis.

The respiratory system regulates blood pH by controlling the levels of CO2; when respiration is impaired (as in conditions such as chronic obstructive pulmonary disease or severe pneumonia), CO2 builds up. As a result of this elevation in CO2, the equilibrium of the bicarbonate buffer system shifts, leading to a higher concentration of hydrogen ions (H+), which in turn lowers the pH.

Thus, the key understanding is that in respiratory acidosis, the imbalance from CO2 retention directly affects acidity levels, causing a significant drop in pH, clearly manifesting as a decreased pH in the context of this question.