A 26-year-old woman presents in winter with headache, dizziness, and nausea after using a faulty gas heater. Vital signs: BP 118/76, HR 102, RR 20, Temp 37.2°C, SpO2 98%. Physical exam reveals pink lips and no respiratory distress. Arterial blood gas shows normal PaO2 (95 mmHg) and carboxyhemoglobin level of 18%. She denies prior respiratory disease. Which mechanism best explains her tissue hypoxia despite normal oxygenation?
- A)Carbon monoxide binding to hemoglobin and shifting the oxygen dissociation curve to the leftGABARITO
- B)Cyanide inhibition of cytochrome oxidase
- C)Reduced inspired oxygen concentration causing low alveolar oxygen tension
- D)Methemoglobin formation causing ferric iron accumulation
- E)Right shifted oxygen dissociation curve from increased 2 3 BPG
Explicação
Carbon monoxide binds hemoglobin with very high affinity and reduces oxygen carrying capacity while also shifting the dissociation curve to the left, impairing oxygen unloading to tissues. PaO2 can remain normal because dissolved oxygen in plasma is unchanged,... Ver explicação completa e trilha adaptativa →