To investigate the occurrence of early diaphragmatic atrophy in mechanically ventilated patients with acute respiratory distress syndrome (ARDS) and evaluate its influence on the outcome of weaning.

A total of 53 mechanically ventilated patients with ARDS admitted to the ICU of Ningbo Medical Center LiHuili Eastern Hospital from January 2019 to June 2021 were enrolled. Diaphragmatic thickness at the end of inspiration (DTei) and diaphragmatic thickness at the end of expiration (DTee) were measured by bedside ultrasound immediately and after 72 h of mechanical ventilation respectively. We defined DTee ≤ 2 mm after 72 h of mechanical ventilation as early diaphragmatic atrophy and patients were divided into the early diaphragmatic atrophy group (group A, n = 27) and the normal group (group B, n = 26) accordingly. The differences in general information, acute physiology and chronic health evaluation (APACHE) Ⅱ score, DTei and DTee immediately and after 72 h of mechanical ventilation, success rate of extubation, and duration of mechanical ventilation between the two groups of patients were compared. The relationships among DTei, DTee and the outcome of weaning were also analyzed. The receiver operating characteristic (ROC) curve was used to assess the optimal cut-off value of DTei, DTee in predicting extubation success.

The alveolar-arterial oxygen pressure difference [P(A-a)O₂] after 72 h of mechanical ventilation [(210 ± 118) mmHg vs. (155 ± 63) mmHg, t = 4.344, P = 0.042] and the duration of mechanical ventilation [188.0 (112.0, 281.0) h vs. 92.5 (71.8,167.8) h, t = 2.642, P = 0.008] in group A were both significantly higher than those in group B accompany with lower success rate of extubation (8/27 vs. 24/26, χ² = 21.751, P < 0.001), lower DTei [(0.224 ± 0.067) cm vs. (0.312 ± 0.094) cm, t = 3.933, P < 0.001] and lower DTee [(0.159 ± 0.027) cm vs. (0.268 ± 0.082) cm, t = 6.570, P < 0.001] after 72 h of mechanical ventilation. Spearman's correlation analysis revealed that the DTei (r = 0.337, P = 0.014) and DTee (r = 0.503, P < 0.001) after 72 h of mechanical ventilation were both positively correlated with extubation success. ROC curve analysis showed that the DTei [area under the curve (AUC) = 0.699, 95% confidence interval (CI) (0.557, 0.817), P = 0.009] and DTee [AUC = 0.797, 95%CI (0.664, 0.895), P < 0.001] after 72 h of mechanical ventilation in ARDS patients both had predictive value for successful mechanical ventilation. The optimal cut-off values are 0.240 cm and 0.200 cm, respectively, with the specificities of 71.4% and 90.5%, respectively.

The occurrence of early diaphragmatic atrophy in mechanically ventilated patients with ARDS is closely related to the adverse weaning outcome. The DTei and DTee after 72 h of mechanical ventilation are both valuable in predicting extubation success of ARDS patients, in which the DTee is more accurate and may be a better indicator compared with the DTei.