Objective To investigate the value of oxygenation index(PaO2 / FiO2 ) in the prediction of mechanical ventilation and prognosis of patients with acute left ventricular failure(ALHF). Methods From January 2011 to May 2015,we enrolled 48 ALHF patients who were admitted into the Department of ICU of People's Hospital of Qiandongnan. At admission, monitored indexes included PaO2 ,PaCO2 ,SaO2 ,SBE,Lac and 6 h Lac,and PaO2 / FiO2 and 6 h lactic acid clearance were calculated at admission. Acute physiology and chronic health(APACHE Ⅱ score)were evaluated. The relation between PaO2 /FiO2 and gender,age,whether mechanical ventilation was conducted,whether death occurred,PaO2 ,PaCO2 ,SaO2 ,SBE, Lac,lactate clearance rate and APACHEⅡ score was analyzed. By making ROC curves,the sensitivity and specificity of PaO2 /FiO2 in the prediction of mechanical ventilation and death were analyzed,and cut - off values were found to make further risk stratification of ALHF. Results The PaO2 / FiO2 of ALHF patients was(196. 7 ± 51. 2);15 patients were administrated with mechanical ventilation and 6 patients died. PaO2 / FiO2 had negative correlation with mechanical ventilation,death,Lac and APACHEⅡ score and had positive correlation with PaO2 and SaO2 ( P ﹤ 0. 05);PaO2 / FiO2 had no obvious correlation with gender,age,hospitalization time,PaCO2 ,SBE and lactate clearance rate(P ﹥ 0. 05). ROC curves showed that when PaO2 /FiO2 was 176. 6,its sensitivity and specificity in the prediction of mechanical ventilation were 81. 8% and 80. 0% with AUC =0. 782 and a OR value of 0. 066;when PaO2 / FiO2 was 150. 8,its sensitivity and specificity in the prediction of mechanical ventilation were 85. 7% and 60. 0% with AUC = 0. 798 and a OR value of 0. 135. Patients ﹤ mechanical ventilation/ death PaO2 /FiO2 cut - off value were higher in APACHEⅡ score than patients ﹥ mechanical ventilation/ death PaO2 / FiO2 cut - off value,and the difference was significant( Z = - 5. 268,P ﹤ 0. 001;Z = - 6. 077,P ﹤ 0. 001). Conclusion PaO2 / FiO2 level could help with the judgment of the severity of ALHF patients and could be used to predict the mechanical ventilation and prognosis of patients.%目的：探讨氧合指数（PaO2/ FiO2）预测急性左心衰竭（ALHF）患者机械通气及预后的价值。方法选择2011年1月—2015年5月黔东南州人民医院 ICU 收治的 ALHF 患者48例，入院立即监测患者氧分压（PaO2）、二氧化碳分压（PaCO2）、氧饱和度（SaO2）、标准碱剩余（SBE）、动脉血乳酸（Lac），入院6 h 再次检测 Lac，计算入院时 PaO2/ FiO2及6 h 乳酸清除率。并予急性生理学与慢性健康状况评分系统Ⅱ（APACHEⅡ）评分。分析 PaO2/ FiO2与性别、年龄、是否机械通气、是否死亡、PaO2、PaCO2、SaO2、SBE、Lac、6 h 乳酸清除率、APACHEⅡ评分的关系，通过绘制受试者工作特征曲线（ROC 曲线），分析 PaO2/ FiO2判断机械通气及死亡的灵敏度和特异度，并找出临界值进一步对 ALHF 进行危险分层。结果 ALHF 患者 PaO2/ FiO2为（196.7±51.2），15例患者行机械通气，6例患者死亡。PaO2/ FiO2与机械通气、死亡、Lac、APACHEⅡ评分呈负相关，与 PaO2、SaO2呈正相关关系（P ﹤0.05）；PaO2/FiO2与性别、年龄、住院时间、PaCO2、SBE、6 h 乳酸清除率无明显相关关系（ P ﹥0.05）。ROC 曲线显示，PaO2/FiO2为176.6时，预测机械通气的灵敏度为81.8％，特异度为80.0％，AUC ＝0.782，OR 值为0.066；PaO2/ FiO2为150.8时，预测死亡的灵敏度为85.7％，特异度为60.0％，AUC ＝0.798，OR 值为0.135。﹤机械通气/死亡 PaO2/ FiO2临界值者的 APACHEⅡ评分均高于﹥机械通气/死亡 PaO2/ FiO2临界值者的 APACHEⅡ评分，差异有统计学意义（Z ＝-5.268，P ﹤0.001；Z ＝-6.077，P ﹤0.001）。结论 PaO2/ FiO2水平可以判断 ALHF 患者病情的严重程度，并可预测是否需要机械通气及预后。
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