[Effects of mechanical ventilation on diaphragmatic contractile function in patients with AECOPD].

OBJECTIVE: To study diaphragmatic strength in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) during mechanical ventilation (MV), and to explore the predictive value of maximal transdiaphragm pressure (Pdi max) for successful extubation.

METHODS: A prospective study was conducted. Twenty-one patients with AECOPD receiving MV admitted to intensive care unit (ICU) of Shanghai East Hospital of Tongji University of School Medicine from February 2015 to May 2017 were enrolled. Pdi max value was measured by using esophageal and gastric balloon catheters within 24 hours of intubation until the day the patient underwent extubation or died. In addition, the C-reactive protein (CRP), serum albumin (Alb) and prealbumin (PA) during MV were recorded. Pearson correlation was used to analyze the correlations between Pdi max and CRP, Alb and PA. The receiver operating characteristic curve (ROC) was used to cumulate Pdi max value of the successful weaning.

RESULTS: Tracheotomy was done in 2 patients, and 2 patients quit the study. The remaining 17 patients were included in the investigative protocol. Six of the 17 patients died and 11 patients were successfully extubated. (1) Mean Pdi max decreased progressively over time in 17 patients of AECOPD during MV. There were no significant changes in Pdi max at 1-2 days of MV. Mean Pdi max at 7 days was significantly lower than that at 3 days [cmH2 O (1 cmH2 O = 0.098 kPa): 20.2±4.2 vs. 28.1±4.4, P < 0.01]. By the end of the evaluation period at 11 days of MV, mean Pdi max decreased about 38.7% to the 1 day of MV (cmH2 O: 19.8±4.7 vs. 32.3±3.9, P < 0.01). During MV, CRP, Alb and PA showed a downward trend. (2) Mean Pdi max and the Pdi max before extubation in patients with difficulty extubation from MV was lower than that in successful weaning [Mean Pdi max (cmH2 O): 25.2±5.4 vs. 28.9±5.8, Pdi max before extubation (cmH2 O): 16.9±2.8 vs. 26.8±6.6, both P < 0.01]. (3) There was significantly negative correlation between Pdi max value and CRP (r = -0.799, P = 0.000). There was significantly positive correlation between Pdi max value and serum Alb (r = 0.613, P = 0.008) and PA (r = 0.661, P = 0.004). (4) ROC curve analysis showed that the area under the ROC curve (AUC) for predicting weaning success in the patients with AECOPD was 0.902. The sensitivity of the diagnosis was 81.8% and the specificity was 100% when cut-off value of Pdi max was 23.2 cmH2 O.

CONCLUSIONS: MV induced the reduction of diaphragmatic contractility in a time-dependent manner. The Pdi max in patients with difficult extubation from MV was lower than that in successful weaning. The Pdi max could be a parameter to predict the successful extubation in patients with AECOPD during MV.