To evaluate the value of diaphragmatic thickening fraction (DTF) assessed by ultrasound in predicting extubation outcomes for ICU patients with mechanical ventilation.

Fifty-two mechanically ventilated patients admitted to the ICU of Taizhou Municipal Hospital and Zhejiang Hospital between June and December 2017 who were being considered for extubation were enrolled. According to the outcome of extubation, 52 patients were divided into the successful extubation group (38 cases) and failed extubation group (14 cases). The general data, respiratory rate, tidal volume, rapid shallow breathing index (RSBI), oxygenation index, diaphragmatic excursion, end-inspiratory diaphragm thickness, end-expiratory diaphragm thickness and DTF at the end of spontaneous breathing trial (SBT) of these two groups were compared. The related factors affecting extubation outcomes were analyzed by Logistic regression and the optimal threshold to predict successful extubation was determined by the receiver operating characteristic (ROC) curve.

The mechanical ventilation time [12 (7, 14) d vs. 16 (11, 17) d], ICU stay [14 (8, 17) d vs. 22 (16, 28) d] and hospital stay [20 (11, 26) d vs. 34 (26, 41) d] before SBT showed statistically significant difference between the successful extubation group and failed extubation group (H = 2.109, 2.881, 3.459; P = 0.035, 0.004, 0.001). At the end of SBT, the respiratory rate [(19 ± 4) breaths/min vs. (22 ± 4) breaths/min], tidal volume [(360 ± 97) mL vs. (285 ± 87) mL], RSBI [(61 ± 22) breaths·min^-1·L^-1 vs. (86 ± 33) breaths·min^-1·L^-1], diaphragmatic excursion [(15 ± 4) mm vs. (11 ± 3) mm], end-inspiratory diaphragm thickness [(2.4 ± 0.6) mm vs. (1.8 ± 0.7) mm] and DTF [(40 ± 9)% vs. (26 ± 7)%] were significantly different between these two groups (t = 2.272, 2.558, 3.154, 3.610, 2.406, 5.180; P = 0.027, 0.014, 0.003, 0.001, 0.020, < 0.001). The mechanical ventilation time before SBT, and respiratory rate, tidal volume, RSBI, diaphragmatic excursion, end-inspiratory diaphragm thickness and DTF at the end of SBT were included in Logistic regression analysis. The results showed that only DTF was a correlative factor for the extubation outcome in ICU patients with mechanical ventilation [odds ratio (OR) = 1.473, 95% confidence interval (CI) (1.054, 2.058), P = 0.023]. With the threshold of > 30.8%, the sensitivity and specificity of DTF in predicting successful extubation were 89.5% and 85.7% respectively. The area under the curve was 0.903 [95%CI (0.760, 1.000), P < 0.001].

For ICU patients receiving SBT, ultrasound evaluation of DTF is a good predictor of extubation outcomes. Diaphragm ultrasound is helpful for early detection of diaphragmatic dysfunction and guidance for extubation in ICU patients with mechanical ventilation.