Which pairing correctly matches an acid-base disorder with its major cause and compensation?

• A. Metabolic acidosis - ketoacidosis/diarrhea - hyperventilation
• B. Metabolic acidosis - vomiting - hyperventilation
• C. Respiratory alkalosis - COPD - hyperventilation
• D. Respiratory acidosis - anxiety - excretion of bicarbonate

Answer: (A)

The key idea being tested is how the body compensates for an acid-base disturbance. In metabolic acidosis, the primary problem is a loss of base (bicarbonate) or an excess of acid, and the body’s rapid response is to hyperventilate to blow off CO2, which helps raise the pH. Classic causes of metabolic acidosis include ketoacidosis and diarrhea, both of which reduce bicarbonate or increase acid. So pairing metabolic acidosis with ketoacidosis or diarrhea and with hyperventilation as the compensatory response fits the physiological pattern.

The other options don’t align with the typical cause-and-compensation relationships: vomiting produces metabolic alkalosis, not acidosis; COPD usually leads to respiratory acidosis rather than respiratory alkalosis; anxiety causes hyperventilation and respiratory alkalosis, not respiratory acidosis, and excretion of bicarbonate is a renal adjustment seen in chronic respiratory acidosis rather than a direct pairing with anxiety.