Which finding would most support a hyperventilation syndrome diagnosis in the described patient?

• A. Hypotension
• B. Hypoxemia
• C. Hypercapnia
• D. Normal oxygen saturation with deep, rapid breathing

Answer: (D)

The key idea is that hyperventilation syndrome produces respiratory alkalosis from excessive ventilation, while oxygenation remains adequate. When someone is hyperventilating, they breathe deeply and rapidly but their lungs are still able to oxygenate the blood well, so oxygen saturation stays normal. The low carbon dioxide level (hypocapnia) from blowing off CO2 is what drives symptoms like dizziness and tingling, not a lack of oxygen. So finding normal oxygen saturation despite deep, rapid breathing fits this diagnosis well.

In contrast, hypotension isn’t a defining feature of hyperventilation alone, and hypoxemia would point to a problem with gas exchange rather than purely anxiety-driven hyperventilation. Hypercapnia (elevated CO2) would be unusual here because the hallmark is blowing off CO2, not retaining it.