NCLEX Oxygenation Practice Test

Rising CO2 levels in the blood directly affect the brain, so confusion or somnolence caused by CO2 retention is a key sign of hypercapnic respiratory failure in COPD. When ventilation falls short, CO2 accumulates (hypercapnia), leading to CNS depression and altered mental status, which clinicians often notice first and use to recognize acute decompensation. The other options don’t specifically point to CO2 buildup: jaundice reflects liver or bile issues; peripheral edema suggests fluid overload or heart failure; bradycardia isn’t a typical hallmark of CO2 retention and can be caused by many unrelated factors. So the mental-status changes driven by CO2 accumulation are the best clue that hypercapnic respiratory failure is occurring.