Extubation Failure Prediction by Echography of the Diaphragm After Cardiothoracic Surgery: The EXPEDIA Study

BACKGROUND: Successful extubation is difficult to predict. Ultrasound measurement of the diaphragm thickening fraction (DTF) might help predict weaning failure after cardiothoracic surgery.

METHODS: We assessed the predictive performance of diaphragm ultrasound in a derivation cohort of 50 prospectively included cardiothoracic surgery subjects ready for a weaning trial and in a validation cohort of 39 subjects ventilated for ≥ 48 h. DTF was assessed by ultrasound during pressure support ventilation (PSV) then during a T-piece spontaneous breathing trial (SBT). DTF was the percentage change in diaphragm thickness between expiration and inspiration and DTF_max, the higher DTF value of the 2 hemidiaphragms. DTF_max during SBT (static study) and the difference in DTF_max between PSV and SBT (dynamic study) were analyzed.

RESULTS: In the derivation cohort, DTF_max during SBT was 25.6 ± 17.3% in subjects with successful extubation and 65.2 ± 17.3% in those with weaning failure (difference 39.7 [95% CI 27.4–51.9], P < .01). During SBT, DTF_max ≥ 50% was associated with weaning failure (area under the receiver operating characteristic curve [AUC] 0.94 ± 0.05). In the dynamic study, a ≥ 40% DTF_max increase was associated with weaning failure (AUC 0.91 ± 0.06). In the validation cohort, DTF_max during SBT was 20.3 ± 17.1% in subjects with successful extubation and 82.0 ± 51.6% in those with weaning failure (difference 61.8 [95% CI 41.6–82.0], P < .01). During SBT, DTF_max ≥ 50% predicted weaning failure (AUC 0.99 ± 0.02). In the dynamic study, a ≥ 40% increase in DTF_max predicted weaning failure (AUC 0.81 ± 0.09).

CONCLUSIONS: Measuring DTF_max during SBT and the DTF_max change when switching from PSV to SBT may help predict weaning failure after cardiothoracic surgery. The study was registered on ANZCTR. Clinical trial registration number: U1111-1180-1999.