Which of the following conditions is NOT a sign of confusion?

• A. Hypoxia
• B. Hypercapnia
• C. Oxygen toxicity
• D. Decompression sickness

Answer: (D)

Confusion signals that the brain isn’t functioning properly, usually from issues with oxygen delivery, ventilation, or CNS exposure to toxins. Hypoxia directly reduces brain oxygen, so brain function becomes unreliable and disoriented thinking or confusion is a common early sign. Hypercapnia, with too much carbon dioxide, also disrupts brain function through CO2 narcosis and acid–base imbalance, leading to confusion and slowed thinking. Oxygen toxicity can produce CNS effects as part of its early signs, including confusion, irritability, dizziness, and even seizures, because high O2 levels directly irritate neural tissue.

Decompression sickness, while it can involve the nervous system, typically presents with signs like joint or muscle pain, cutaneous symptoms, dizziness, visual disturbances, or focal neurological deficits such as numbness or weakness. Confusion by itself is not a defining or primary sign of DCS, so it’s not considered a classic indicator in this context.