Electrical impedance tomography-derived flow index during spontaneous breathing trial stratifies the risk of reintubation within 48 h after extubation

BACKGROUND: Spontaneous breathing trial (SBT) is the standard test of readiness for liberation from invasive mechanical ventilation, but some patients who successfully complete SBT still experience early post-extubation failure. Inspiratory effort during SBT has emerged as an important physiological determinant of weaning tolerance and extubation outcome because it reflects the balance between ventilatory load and respiratory muscle capacity, yet its assessment often requires airway occlusions, dedicated ventilator algorithms, or intermittent measurements. We therefore evaluated whether an electrical impedance tomography (EIT)-derived flow index (EFI) measured during SBT was associated with SBT outcome and with reintubation within 48 h after extubation. METHODS: In this prospective multicenter observational study, mechanically ventilated adults receiving invasive ventilation for at least 48 h underwent a standardized 30-min pressure support SBT with continuous EIT monitoring. EFI was calculated breath by breath from EIT-derived inspiratory flow-time profiles. The primary endpoint was SBT outcome. A prespecified key secondary endpoint was reintubation within 48 h after planned extubation among patients who successfully completed the SBT and underwent extubation according to routine care. EFI discrimination for SBT failure was assessed using receiver operating characteristic analysis. For the post-extubation analysis, 48-h freedom from reintubation was evaluated using Kaplan-Meier analysis and Cox proportional hazards models. RESULTS: A total of 150 patients were enrolled, of whom 107 successfully completed the SBT and underwent planned extubation. EFI showed excellent discrimination for the primary endpoint of SBT outcome (AUC 0.980) and provided early physiological warning of evolving SBT intolerance. Reintubation within 48 h occurred in 7 of 107 extubated patients. Using the EFI threshold of 1.333 derived from the primary endpoint analysis, patients with EFI < 1.333 had significantly lower 48-h freedom from reintubation than those with EFI ≥ 1.333, and all reintubation events occurred in the EFI < 1.333 group. In univariable Cox analyses, EFI, RSBI, MIP, and P0.1 were each associated with reintubation within 48 h after extubation. Because of severe multicollinearity among these indices and the very small number of events, a combined multivariable model was not pursued. CONCLUSIONS: EFI measured during SBT was strongly associated with SBT outcome and showed an exploratory association with reintubation within 48 h after extubation. Beyond identifying SBT intolerance, EFI may help identify patients with residual physiological vulnerability after a successful SBT; however, this secondary finding requires cautious interpretation and external validation. TRIAL REGISTRATION: ClinicalTrials.gov NCT06876792. Registered on March 10, 2025.