Which symptom is most characteristic of advanced hypoxia at high altitude?

Which symptom is most characteristic of advanced hypoxia at high altitude?

• A. Blurred vision
• B. Sneezing
• C. Frequent yawning
• D. Skin rash

Answer: (A)

When oxygen delivery to tissues drops at high altitude, the nervous system is among the first to show trouble. Advanced hypoxia affects brain and eye function, so visual processing becomes impaired. Blurred vision happens because the optic nerve and retinal tissues require a steady oxygen supply, and as they receive less, vision softens or becomes fuzzy. This makes blurred vision a clear and characteristic warning sign of severe oxygen deficiency. Other symptoms listed aren’t reliable indicators of advanced hypoxia: sneezing is just a nasal reflex, frequent yawning can be due to fatigue or other factors, and a skin rash isn’t related to oxygen levels in the blood. Seeing blurred vision should prompt immediate action—descend and re‑establish adequate oxygen.

When oxygen delivery to tissues drops at high altitude, the nervous system is among the first to show trouble. Advanced hypoxia affects brain and eye function, so visual processing becomes impaired. Blurred vision happens because the optic nerve and retinal tissues require a steady oxygen supply, and as they receive less, vision softens or becomes fuzzy. This makes blurred vision a clear and characteristic warning sign of severe oxygen deficiency.

Other symptoms listed aren’t reliable indicators of advanced hypoxia: sneezing is just a nasal reflex, frequent yawning can be due to fatigue or other factors, and a skin rash isn’t related to oxygen levels in the blood. Seeing blurred vision should prompt immediate action—descend and re‑establish adequate oxygen.