In an acute COPD exacerbation, the arterial blood gas typically shows which combination?

• A. Hyperoxia with alkalemia
• B. Hyperoxemia without acid-base disturbance
• C. Hypoxemia with hypercapnia and possible acidemia
• D. Normal ABG values

Answer: (C)

During an acute COPD flare, airways are inflamed and mucus narrows the airways, causing areas of the lung to be poorly ventilated. This leads to ventilation-perfusion mismatch and overall hypoventilation, so arterial oxygen drops and carbon dioxide builds up.

The typical ABG pattern reflects this: low PaO2 (hypoxemia) and high PaCO2 (hypercapnia) with a tendency toward acidemia because the excess CO2 lowers the blood pH. In someone with chronic COPD, there can be metabolic compensation (higher bicarbonate) that may blunt the pH change, but in an acute exacerbation the acidemia from CO2 retention is a common finding.

So the best description is hypoxemia with hypercapnia and possible acidemia. The other patterns (hyperoxia with normal pH, hyperoxemia without acid-base disturbance, or normal ABG) don’t fit the expected gas exchange impairment seen in an acute COPD flare.