病人被診斷為肺栓塞，哪項護理行動是優先的？

核心概念：肺栓塞（Pulmonary Embolism, PE）的緊急護理。 為何正確答案對： A. 肺栓塞會阻礙血液流向肺部進行氣體交換，導致嚴重的低血氧（Hypoxia）和呼吸窘迫（Respiratory distress）。改善氧合是處理急性 PE 的首要任務，能立即緩解症狀，穩定生命徵象，並為後續診斷與治療爭取時間。這是遵循 ABC（Airway, Breathing, Circulation）原則中「B」（Breathing）的優先級。 為何其他選項錯： B. 檢測 D-dimer 是診斷 PE 的輔助檢查，但它不能立即改善病人的缺氧狀況，且結果可能受其他因素影響，不適合作為急性處置的優先項。 C. 靜脈輸注點滴（Initiate IV fluids）本身無法直接改善肺部氣體交換，除非病人有低血容量，但即使如此，氧氣治療仍是更直接的急救措施。 D. 準備進行電腦斷層掃描（CT scan）是診斷 PE 的重要步驟，但這是在病人生命徵象相對穩定後進行的，不能取代立即的生命支持措施。

Core concept: emergency nursing care of pulmonary embolism (PE). Why the correct answer is right: A. Pulmonary embolism obstructs blood flow to the lungs for gas exchange, leading to severe hypoxia and respiratory distress. Improving oxygenation is the top priority in the acute management of PE; it immediately relieves symptoms, stabilizes vital signs, and buys time for subsequent diagnostic workup and treatment. This aligns with the 'B' (Breathing) priority of the ABC (Airway, Breathing, Circulation) principle. Why the other options are wrong: B. D-dimer is an adjunctive diagnostic test for PE, but it does not immediately correct the client's hypoxia, and results may be confounded by other factors, making it inappropriate as the priority acute intervention. C. Initiating IV fluids does not directly improve pulmonary gas exchange unless the client is hypovolemic; even then, oxygen therapy remains the more direct emergent intervention. D. Preparing for a CT scan is a key step in diagnosing PE, but it is performed only after the client's vital signs are relatively stable and cannot replace immediate life-supporting measures.