Acta Anaesthesiol Scand. 2019;00:1–9. wileyonlinelibrary.com/journal/aas | 1 © 2019 Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd 1 | INTRODUCTION Mechanical ventilation (MecV) is frequently a part of the armamen- tarium for respiratory support in critically ill subjects. However, it is still difficult to predict which subjects will be successfully weaned and extubated. This is of major clinical relevance since reintubation is associated with higher mortality 1 and increased costs. 2 Many clinical parameters and scores have been proposed to pre- dict extubation success but with only mild to moderate accuracy. 3-6 More recently, electrical impedance tomography (EIT) has gained much interest as a useful bedside, noninvasive, continuous monitor- ing tool in mechanically ventilated subjects. It is capable of obtaining real-time, two-dimensional, cross-sectional images of the thorax, helping to evaluate the air distribution across the lungs. Its utility has been documented in many scenarios, including pneumothorax, 7,8 pulmonary edema, 9,10 positive end-expiratory pressure (PEEP) titra- tion after recruitment maneuvers, 11-13 endotracheal tube position 14 , and dynamic hyperinflation. 15 Received: 20 November 2018 | Revised: 11 March 2019 | Accepted: 10 April 2019 DOI: 10.1111/aas.13383 ORIGINAL ARTICLE Electrical impedance tomography monitoring during spontaneous breathing trial: Physiological description and potential clinical utility Júlia N. G. Lima 1 | Melissa S. Fontes 1 | Tatiana Szmuszkowicz 1 | Alexandre M. Isola 2 | Alexandre T. Maciel 3 1 São Luiz Hospital, Itaim Unity, Adult Intensive Care Unit, São Paulo, Brazil 2 Imed Continued Medical Education Department, São Paulo, Brazil 3 Imed Research Department, São Paulo, Brazil Correspondence Alexandre T. Maciel, Imed Research Department, Rua Fabia 610 apt 24A Vila Romana, Zip 05051-030, São Paulo-SP, Brazil. Email: alexandre.toledo@imedgroup.com.br Background: Readiness for mechanical ventilation (MecV) weaning and extubation is usually assessed clinically with the use of a spontaneous breathing trial (SBT), but its accuracy is limited, and the pathophysiology of weaning failure not completely elucidated. The purpose of the present study was to describe the physiological be- havior of electrical impedance tomography parameters during SBT and to propose additional variables that could be helpful in defining weaning/extubation outcome. Methods: From December 2015 to January 2017, all subjects who remained under MecV with an orotracheal tube for more than 24 hours and who were submitted to SBT both in pressure-support ventilation (PSV) or T-tube were included in the study. Both clinical and impedance parameters were collected immediately before as well as during SBT. Results: Forty-two subjects were included in the final analysis. For subjects submit- ted to SBT in PSV, none of the impedance parameters added significant information regarding weaning outcomes. For subjects submitted to a T-tube SBT, a significant and progressive decrease in end-expiratory lung impedance (dEELI) was observed, which was more prominent in subjects who clinically failed the SBT. These subjects had a significant rapid shallow breathing index at the end of SBT. Conclusions: dEELI was a potentially useful parameter in the evaluation of MecV weaning outcome when abrupt lung depressurization was induced during SBT in our study. The degree of dEELI decrease was probably related to the magnitude of lung derecruitment, which seems to play a key role in the MecV weaning outcome.