What observation best indicates hypoxia?

• A. Clear skin and mucous membranes
• B. Cyanosis
• C. Normal oxygen saturation
• D. Loud breath sounds

Answer: (B)

Hypoxia means tissues aren’t getting enough oxygen, and a key visible clue is cyanosis—the bluish discoloration of the lips, tongue, and mucous membranes. This happens when there’s more deoxygenated hemoglobin circulating as oxygen levels fall, so the blood appears blue-tinged despite how the person looks overall. It’s a practical, bedside sign that oxygen delivery is insufficient. The other observations don’t point as directly to low oxygen: skin and mucous membranes can be normal when oxygen delivery is adequate; a normal oxygen saturation reading argues against hypoxia (though readings can be misleading in some situations); and loud breath sounds reflect airway or lung issues but don’t by themselves confirm systemic hypoxia.