What ABG pattern is commonly seen in bronchiectasis with infection?

• A. Respiratory acidosis with hypercapnia
• B. Metabolic acidosis
• C. Normal ABG
• D. Acute alveolar hyperventilation with hypoxemia

Answer: (D)

In bronchiectasis with infection, the airways are inflamed and clogged with mucus, creating areas where ventilation doesn’t meet perfusion (V/Q mismatch). The body responds to the resulting hypoxemia and increased work of breathing by hyperventilating, at least initially. This acute alveolar hyperventilation drives CO2 out of the blood, so the ABG shows a respiratory alkalosis pattern (high pH, low PaCO2) while oxygen tension remains low due to the mismatch. So the characteristic ABG is respiratory alkalosis with hypoxemia. As the illness progresses and fatigue worsens, ventilation can falter and CO2 may rise, but in the acute infectious phase the hyperventilation with hypoxemia is the expected pattern.