膈肌增厚分数指导慢性阻塞性肺疾病机械通气患者撤机的临床研究

目的：通过床旁超声评估慢性阻塞性肺疾病机械通气患者的膈肌功能，明确膈肌超声指标对撤机的指导价值。方法研究对象为2015年2月至2015年8月浙江大学附属邵逸夫医院危重医学科诊治的需行有创机械通气的慢性阻塞性肺疾病患者。在患者符合临床撤机筛查条件后进行自主呼吸试验1h。自主呼吸试验结束时采用床旁 B 型超声评估患者膈肌指标，包括吸气末膈肌厚度（ diaphragmatic thickness at the end of inspiration， DTei）、呼气末膈肌厚度（ diaphragmatic thickness at the end of expiration， DTee）、膈肌增厚分数（ diaphragmatic thickening fraction， DTF），同时记录浅快呼吸指数及其他生理参数。对符合临床撤机标准者进行撤机。统计分析膈肌超声指标与撤机结果之间的关系，采用接受者操作特征曲线（ ROC）分别评价DTF和浅快呼吸指数对撤机成功的预测价值。结果共43例患者纳入本研究，其中撤机成功25例，撤机失败18例。撤机成功组和失败组的撤机前参数如年龄、体质量指数、急性生理学和慢性健康状况评分Ⅱ、机械通气时间、心率、平均动脉压、分钟通气量、氧合指数等差异均无统计学意义（ P＞0.05）。膈肌静态指标DTei、 DTee在撤机成功组和失败组之间差异无统计学意义（ P＞0.05）。撤机成功组撤机前的DTF （39.66±13.22）％vs.（23.84±8.85）％显著高于撤机失败组（P＜0.05）。以DTF≥30％为标准预测撤机成功，敏感度84％，特异度83.33％， ROC曲线下面积0.872（95％ CI：0.759～0.985）。撤机成功组撤机前的浅快呼吸指数（62.74±26.05） vs.（98.89±35.44）显著低于撤机失败组（ P＜0.05）。以浅快呼吸指数≤105为标准预测撤机成功，敏感度92％，特异度38.89％， ROC 曲线下面积0.804（95％ CI：0.669～0.940）。结论膈肌超声指标DTF对慢性阻塞性肺疾病机械通气患者撤机时机选择和撤机结果预测具有指导作用。

Diaphragm thickening fraction as a predictor of successful weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease

Objective To evaluate the predictive performance of diaphragm thickening fraction ( DTF) assessed by ultrasound in the feasibility of weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease ( COPD ) . Methods Forty-three patients with COPD were enrolled for prospective study.All patients were ventilated mechanically for more than 48 hours and were expected to be weaned when they met clinical criteria in the intensive care unit from February 2015 to August 2015.Patients received a spontaneous breathing trial under pressure support for 1 h.At the end of spontaneous breathing trial, the right hemi-diaphragm was visualized in the zone of apposition using a 6-13 MHz linear ultrasound probe. Diaphragm thickness was recorded at end-inspiration (DTei) and end-expiration (DTee), and the DTF was calculated as percentage from the following formula:(DTei -DTee) /DTee.Also the rapid shallow breathing index ( RSBI ) was calculated.Patients meeting weaning criteria were extubated.Weaning successfully was defined as spontaneous breathing for >48 h without any form of ventilation support.Results Twenty-five patients were weaned successfully and failure of weaning was found in 18 patients.A significant differences in DTF ( 39.66 ±13.22 )%vs.( 23.84 ±8.85 )%, P <0.05 and RSBI ( 62.74 ±26.05 ) vs.( 98.89 ± 35.44) , P <0.05 were observed between patients with successful weaning and patients with failure.The sensitivity and specificity of DTF≥30 % for successful weaning were 84% and 83.88 %, respectively.The area under the receiver operating characteristic curve was 0.872 ( 95 % CI: 0.759-0.985 ) for DTF.By comparison, when RSBI was ≤105, there was a sensitivity of 92 %, and a specificity of 38.89 % for determining successful weaning.The area under the receiver operating characteristic curve was 0.804 ( 95 %CI: 0.669-0.940) for RSBI. Conclusions This study shows that in a cohort of COPD patients, the assessment of DTF using diaphragm ultrasound may be useful to predict success weaning or failure during spontaneous breathing trial.