Abstract: Background　Weaning from mechanical ventilation is associated with a high failure rate in sepsis patients.Although in recent years，ultrasound has been widely used in the management of critically ill patients before weaning from mechanical ventilation，such as evaluating the cardiac function，chest ultrasound is rarely used in the process of weaning from mechanical ventilation in patients with sepsis.Objective　To investigate the value of chest ultrasound in predicting the outcome of weaning from mechanical ventilation in patients with sepsis.Methods　A prospective study was conducted.Sixty-five patients with sepsis who underwent continuous mechanical ventilation for more than 48 hours in the ICU，Cixi Hospital Affiliated to WenZhou Medical University from June 2017 to December 2018 were enrolled.For those meeting the screening criteria of weaning from mechanical ventilation，spontaneous breathing trial（SBT） was performed using low level pressure support ventilation，and chest ultrasound was implemented before and 30 minutes after SBT，and parameters including lung ultrasound score（LUS），diaphragmatic excursion，diaphragmatic thickness at end-inspiration and diaphragmatic thickness at end-expiration as well as calculated rapid shallow breathing index（RSBI），diaphragmatic rapid shallow breathing index（D-RSBI） and diaphragmatic thickening fraction（DTF） were collected.Weaning from mechanical ventilation was performed in the eligible cases，and the aforementioned parameters were compared between those with successful and failed weaning（good weaning outcome was defined as successful weaning）.ROC curve analysis was conducted to evaluate the values of chest ultrasound parameters in predicting the outcome of weaning from mechanical ventilation.Results　Fifty cases were finally enrolled，including 35 with successful weaning，and 15 with failed weaning.There were significant differences in mean levels of post-SBT LUS，pre-SBT DTF，post-SBT DTF as well as post-SBT D-RBSI between the two groups（P<0.05）.The mean LUS level increased significantly after SBT than before in those with failed weaning（P<0.05）.The mean DTF level showed an obvious increase after SBT before in both groups（P<0.05）.In predicting the outcome of weaning from mechanical ventilation，the AUC of post-SBT LUS was 0.819，and a good outcome may be estimated when the cutoff point was determined as less than 15.5 scores with a sensitivity of 0.730 and a specificity of 0.800.The AUC of post-SBT D-RSBI was 0.895，and a good outcome may be estimated when the cutoff point was determined as less than 1.41 times?min-1?mm-1 with a sensitivity of 0.867 and a specificity of 0.829.The AUC of pre-SBT DTF was 0.738，and a good outcome may be estimated when the cutoff point was determined as greater than 22.9% with a sensitivity of 0.866 and a specificity of 0.667.The AUC of post-SBT DTF was 0.891，and a good outcome may be estimated when the cutoff point was determined as greater than 33.2% with a sensitivity of 0.886 and a specificity of 0.867.Conclusion　Chest ultrasound has predictive value for the result of weaning in patients with sepsis.Post-SBT LUS<15.5 scores in combination with post-SBT D-RSBI<1.41?min-1?mm-1 and post-SBT DTF>33.2% predicts high rate of successful weaning.

Key words: Ultrasonography；Thorax；；Ventilators, mechanical；Sepsis；；Weaning

摘要： 背景　脓毒症患者机械通气撤机失败率较高，近年来超声已广泛应用于重症患者机械通气撤机评估中，如评估撤机前患者的心功能，但在脓毒症患者机械通气撤机过程中胸部超声应用不多。目的　探讨胸部超声对脓毒症患者机械通气撤机结果的预测价值。方法　采用前瞻性研究，2017年6月—2018年12月选择温州医科大学附属慈溪医院重症医学科收治的65例持续机械通气48 h以上的脓毒症患者，在其符合机械通气撤机筛查条件后采用低水平压力支持通气（PSV）进行自主呼吸试验（SBT），于SBT前及SBT 30 min后进行胸部超声指标检测，获得肺部超声评分（LUS）、膈肌位移值（DE）、吸气末膈肌厚度（DTei）和呼气末膈肌厚度（DTee），并计算浅快呼吸指数（RSBI）、膈肌浅快呼吸指数（D-RBSI）和膈肌增厚分数（DTF）。对符合临床撤机标准者进行撤机，根据撤机结果将患者分为撤机成功组和撤机失败组。比较两组患者各项指标的差异，采用受试者工作特征（ROC）曲线评估胸部超声对脓毒症患者机械通气撤机结果的预测价值。结果　最终纳入50例患者，其中撤机成功组35例，撤机失败组15例。撤机成功组与撤机失败组患者SBT后LUS、SBT前DTF、SBT后DTF、SBT后D-RBSI比较，差异有统计学意义（P<0.05）。撤机失败组患者SBT后LUS较SBT前上升（P<0.05），撤机成功组和撤机失败组患者SBT后DTF均高于SBT前（P<0.05）。SBT后LUS、D-RSBI及SBT前后DTF预测脓毒症患者机械通气撤机结果的ROC曲线下面积（AUC）分别为0.819、0.895、0.738、0.891。SBT后LUS<15.5分、SBT后D-RSBI<1.41次?min-1?mm-1、SBT前DTF>22.9%、SBT后DTF>33.2%预测脓毒症患者机械通气撤机成功的灵敏度分别为0.730、0.867、0.866、0.886，特异度分别为0.800、0.829、0.667、0.867。结论　胸部超声对脓毒症患者撤机结果有预测价值，SBT后LUS<15.5分、D-RSBI<1.41次?min-1?mm-1、DTF>33.2%对撤机成功的预测价值高。

关键词: 超声检查；胸部；通气机, 机械；脓毒症；撤机