COPD USMLE Step 1 Practice Question
A 40 year old man is found unconscious in his garage with the car engine running. In the emergency department he is confused and reports headache. Pulse oximetry reads 99 percent. Arterial blood gas shows a normal partial pressure of oxygen. Which of the following best explains his tissue hypoxia?
Answer choices
- AReduced oxygen carrying capacity and impaired oxygen unloadingCorrect answer
- BDecreased dissolved oxygen content in plasma
- CReduced pulmonary compliance due to surfactant deficiency
- DIncreased methemoglobin formation from nitrite exposure
- EVentilation perfusion mismatch due to pulmonary arterial obstruction
- FMitochondrial dysfunction due to cyanide poisoning
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.