Why does administering supplemental oxygen to a patient with severe chronic obstructive pulmonary disease (COPD) sometimes paradoxically worsen their hypercapnia, leading to respiratory acidosis?

💡 Explanation

In severe COPD, ventilation-perfusion (V/Q) matching is severely impaired. Supplemental oxygen blunts the hypoxic drive that maintains ventilation in poorly perfused areas; because this mechanism fails, CO2 removal is reduced, therefore, hypercapnia worsens, rather than improving as it would in a healthy lung.

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