Ventilation distribution during spontaneous breathing trials predicts liberation from mechanical ventilation: the VISION study

Background: Predicting complete liberation from mechanical ventilation (MV) is still challenging. Electrical impedance tomography (EIT) offers a non-invasive measure of regional ventilation distribution and could bring additional information.

Research question: Whether the display of regional ventilation distribution during a Spontaneous Breathing Trial (SBT) could help at predicting early and successful liberation from MV.

Study design and methods: Patients were monitored with EIT during the SBT. The tidal image was divided into ventral and dorsal regions and displayed simultaneously. We explored the ventral-to-dorsal ventilation difference in percentage, and its association with clinical outcomes. Liberation success was defined pragmatically as passing SBT followed by extubation within 24 h without reintubation for 7 days. Failure included use of rescue therapy, reintubation within 7 days, tracheostomy, and not being extubated within 24 h after succesful SBT. A training cohort was used for discovery, followed by a validation cohort.

Results: Among a total of 98 patients analyzed, 85 passed SBT (87%), but rapid liberation success occurred only in 40; 13.5% of extubated patients required reintubation. From the first minutes to the entire SBT duration, the absolute ventral-to-dorsal difference was consistently smaller in liberation success compared to all subgroups of failure (p < 0.0001). An absolute difference at 5 min of SBT > 20% was associated with failure of liberation, with sensitivity and specificity of 71% and 78% and positive predictive value 81% in a validation cohort.

Conclusion: During SBT, a large ventral-to-dorsal difference in ventilation indicated by EIT may help to rapidly identify patients at risk of liberation failure.