氣切可以改善病人的舒適度和口腔衛生，以及方便照護等好處，然而需要長期使用呼吸器之重症病人的氣切時機（早期或晚期氣切）仍是未知。本文目的係以實證觀點探討長期使用呼吸器之重症病人氣切的時機。我們執行系統性文獻搜尋，包括公共醫學資料庫、Trip資料庫、考科藍資料庫、中文電子期刊服務網。利用布林邏輯、醫學主題詞表和相對應的關鍵字進行搜尋。資料搜尋不限定語言。我們選入一篇符合PICO的相關文獻，它包括4篇具高風險偏差之研究，共納入673位病人。早期氣切與晚期氣切之間對病人死亡率無顯著差異。其中一篇研究結果顯示，早期氣切可以有意義縮短病人使用呼吸器的天數。本篇考科藍文獻無法提供足夠的證據對重症病人的氣切時機做出建議，早期氣切和晚期氣切二者之間的差異性需要更多高質量的隨機對照試驗來證實。

Benefits of tracheotomy include improved patientcomfort, better oral hygiene, and easier nursing care. However, the timing (early vs. late) of the tracheotomy in critically ill patients requiring prolonged mechanical ventilation (PMV) remains unclear. The objective of this article was to systematically explore the evidence on timing of tracheostomy in critically ill patients predicted to beon PMY. A systematic literature search of PubMed, Trip database, the Cochrane Library, and the Chinese Electronic Periodical Service was conducted using specific search terms. Electronic searches were performed using Boolean logic, Medical Subject Headings, and the appropriate corresponding keywords. We did not impose any language restriction in database searches. We selected one relevant literaturewhich met our PICO. It included four studieswith a high risk of bias, in which a total of 673 patients were randomized to either early or late tracheostomy. There was no significant difference between early and late tracheostomies for patient mortality. In one study a statistically significant result favouring early tracheostomy was observed in the outcome measuring time spent on ventilator support. The evidence in this Cochrane reviewis insufficient to recommendeither early or late tracheostomy for critically ill patients. Additional high quality randomized controlled trials are necessary to evaluate possible differences between early and late tracheostomyfor critically ill patients.