A 28-year-old woman from Delhi presents to the emergency department with severe vomiting and abdominal pain for 6 hours. She has a history of type 1 diabetes mellitus. On examination, she is tachypneic (RR 28/min), with Kussmaul breathing. Arterial blood gas shows: pH 7.18, PaCO₂ 22 mmHg, HCO₃⁻ 8 mEq/L, PaO₂ 95 mmHg. Her oxygen saturation on room air is 98%. Despite adequate oxygenation and normal hemoglobin (14 g/dL), her tissues appear poorly perfused. Which of the following best explains the impaired oxygen delivery to tissues in this patient?