A 28-year-old male factory worker is brought to the emergency department 15 minutes after suspected inhalation of hydrogen cyanide gas during an industrial accident. He is conscious but confused, with rapid shallow breathing (RR 32/min), heart rate 118/min, and blood pressure 140/88 mmHg. Skin appears flushed and warm. Arterial blood gas shows pH 7.28, PaCO₂ 32 mmHg, HCO₃⁻ 14 mEq/L, and normal PaO₂ of 95 mmHg on room air. What is the primary mechanism of toxicity in this patient?