The main cause of respiratory acidosis is which of the following?

• A. An excess of bicarbonate in the body
• B. Excess carbon dioxide retention
• C. A deficiency of bicarbonate in the body
• D. Excess carbon dioxide excretion

Answer: (B)

In respiratory acidosis, the main issue is failure to remove carbon dioxide, so CO2 builds up in the blood. CO2 combines with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. When CO2 rises, more hydrogen ions appear, lowering the pH and causing acidosis. The body’s buffering systems, including the kidneys, may compensate over time by increasing bicarbonate, but the immediate problem is CO2 retention from hypoventilation or obstructed airways.

Excess bicarbonate would raise the pH rather than lower it, representing a different disturbance. A deficiency of bicarbonate tends to cause metabolic acidosis, not respiratory. Exhaling too much CO2 would reduce acidity, potentially causing alkalosis, which again is the opposite of respiratory acidosis.