A patient who appears very anxious enters the office complaining of dizziness with perioral and extremity paresthesias. She vaguely describes some chest discomfort. Physical examination is unremarkable, except for moderate tachypnea with obvious sighing respiration. This clinical picture is most consistent with

• A. Bronchial asthma
• B. Hyperventilation syndrome
• C. Spontaneous pneumothorax
• D. Anaerobial emphysema

Answer: (B)

Rapid, anxiety-driven breathing causes respiratory alkalosis from excess CO2 loss, leading to dizziness and tingling around the mouth and in the extremities. The sighing, tachypneic pattern with a largely benign exam is classic for hyperventilation syndrome, where the lowered CO2 shifts calcium binding and increases neural excitability, producing paresthesias and chest discomfort. In contrast, asthma would typically show wheezing and expiratory obstruction, and a pneumothorax would present with sudden pleuritic chest pain and abnormal breath sounds on one side. The described presentation aligns best with hyperventilation due to anxiety.