Question

in chronic obstructive pulmonary disease (copd), decreased carbon dioxide elimination results in increased carbon dioxide tension in arterial blood, leading to which of the following acid - base imbalances?
metabolic alkalosis
metabolic acidosis
respiratory acidosis
respiratory alkalosis

Explanation:

In COPD, decreased CO₂ elimination means CO₂ accumulates. CO₂ combines with water to form carbonic acid ($\ce{CO_{2} + H_{2}O <=> H_{2}CO_{3}}$), increasing acid in blood. Respiratory acidosis is due to impaired ventilation (like in COPD) causing elevated $\ce{PaCO_{2}}$ (arterial CO₂ tension) and increased carbonic acid, leading to acid-base imbalance. Metabolic imbalances relate to non - respiratory acid - base changes (e.g., bicarbonate), so metabolic alkalosis/acidosis are incorrect. Respiratory alkalosis is from too much CO₂ elimination (e.g., hyperventilation), opposite of COPD's CO₂ retention.

Answer:

C. Respiratory acidosis