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.

Key Points

1. Predictive Role of Ventilation Distribution: Electrical impedance tomography (EIT) was used to assess regional ventilation distribution during spontaneous breathing trials (SBTs), demonstrating that increased ventral-to-dorsal ventilation heterogeneity was associated with weaning failure.
2. Study Population and Methods: The study included 98 mechanically ventilated patients, divided into training and validation cohorts, all undergoing SBTs while monitored with EIT to evaluate regional ventilation patterns.
3. Definition of Liberation Success and Failure: Success was defined as passing the SBT followed by extubation within 24 hours without reintubation for seven days. Failure included the need for rescue therapy, reintubation within seven days, or failure to extubate within 24 hours after a successful SBT.
4. Key Finding on Ventilation Distribution: Patients with a smaller ventral-to-dorsal difference in ventilation (less than 20%) were more likely to achieve successful liberation from MV, while those with a larger difference (>20%) had a significantly higher risk of failure.
5. Early Detection of Liberation Failure: The absolute ventral-to-dorsal difference, measured as early as five minutes into the SBT, reliably predicted extubation outcomes, with sensitivity and specificity rates of 71% and 78%, respectively.
6. Comparison with Other Predictive Measures: Traditional indicators like the rapid shallow breathing index (RSBI), airway occlusion pressure (P0.1), and lung ultrasound scores (LUSS) were less effective at predicting MV liberation outcomes than the ventral-to-dorsal difference measured by EIT.
7. Impact of Neurological Conditions: Patients intubated due to neurological conditions had a higher likelihood of weaning failure, highlighting the need for individualized extubation strategies in this population.
8. Clinical Implications for Weaning Protocols: The study suggests that integrating EIT into clinical practice may improve decision-making regarding extubation timing, potentially reducing unnecessary reintubation and prolonged ventilation.
9. Limitations and Generalizability: The study was conducted in a single-center ICU with a high proportion of patients intubated for neurological reasons, which may limit the generalizability of findings to other ICU populations.
10. Future Research Directions: Further studies are needed to validate these findings in diverse patient populations and to explore the integration of EIT into routine weaning protocols to improve MV liberation success rates.

ACCESS FULL ARTICLE HERE

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.