Electrical impedance tomography during spontaneous breathing trials and after extubation in critically ill patients at high risk for extubation failure: a multicenter observational study

Abstract

Background: This study aims to assess the changes in lung aeration and ventilation during the first spontaneous breathing trial (SBT) and after extubation in a population of patients at risk of extubation failure.

Methods: We included 78 invasively ventilated patients eligible for their first SBT, conducted with low positive end-expiratory pressure (2 cm H2O) for 30 min. We acquired three 5-min electrical impedance tomography (EIT) records at baseline, soon after the beginning (SBT_0) and at the end (SBT_30) of SBT. In the case of SBT failure, ventilation was reinstituted; otherwise, the patient was extubated and two additional records were acquired soon after extubation (SB_0) and 30 min later (SB_30) during spontaneous breathing. Extubation failure was defined by the onset of post-extubation respiratory failure within 48 h after extubation. We computed the changes from baseline of end-expiratory lung impedance (∆EELI), tidal volume (∆Vt%), and the inhomogeneity index. Arterial blood was sampled for gas analysis. Data were compared between sub-groups stratified for SBT and extubation success/failure.

Results: Compared to SBT success (n = 61), SBT failure (n = 17) showed a greater reduction in ∆EELI at SBT_0 (p < 0.001) and SBT_30 (p = 0.001) and a higher inhomogeneity index at baseline (p = 0.002), SBT_0 (p = 0.003) and SBT_30 (p = 0.005). RR/Vt was not different between groups at baseline but was significantly greater at SBT_0 and SBT_30 in SBT failures, compared to SBT successes (p < 0.001 for both). No differences in ∆Vt% and arterial blood gases were observed between SBT success and failure. The ∆Vt%, ∆EELI, inhomogeneity index and arterial blood gases were not different between patients with extubation success (n = 39) and failure (n = 22) (p > 0.05 for all comparisons).

Conclusions: Compared to SBT success, SBT failure was characterized by more lung de-recruitment and inhomogeneity. Whether EIT may be useful to monitor SBT remains to be determined. No significant changes in lung ventilation, aeration or homogeneity related to extubation outcome occurred up to 30 min after extubation. Trial registration Retrospectively registered on clinicaltrials.gov (Identifier: NCT03894332; release date 27th March 2019).

Keywords: Electrical impedance tomography; Extubation failure; Mechanical ventilation; Post-extubation respiratory failure; Spontaneous breathing trial; Weaning.

Conflict of interest statement

Dr. Navalesi’s research laboratory has received equipment and grants from Maquet Critical Care, Draeger and Intersurgical S.p.A. He also received honoraria/speaking fees from Maquet Critical Care, Orionpharma, Philips, Resmed, MSD and Novartis. Dr. Navalesi contributed to the development of the helmet Next, whose licence for patent belongs to Intersurgical S.P.A., and receives royalties for that invention. Dr. Longhini and Dr. Navalesi contributed to the development of a new device not discussed in the present study whose patent is in progress (European Patent application number EP20170199831). The remaining authors have disclosed that they do not have any Competing interests.

Figures

Fig. 1

Patients’ flow throughout the study protocol. Of the overall population of 78 patients who underwent data analysis, 61 patients (78.2%) successfully passed the SBT (i.e., SBT success), whereas 17 (21.8%) did not (i.e., SBT failure). Of the 61 successfully extubated patients, 22 patients (34.9%) met one or more criteria for post-extubation respiratory failure. Among these 22 patients who experienced extubation failure, three individuals (14.9%) required immediate reintubation, while in 19 patients (86.4%) CPAP/NIV was attempted as rescue therapy. Of these 19 patients, 8 (42.1%) failed and were reintubated. Not reported in the figure is that none of the reintubated patients required tracheostomy, and only one patient died 10 days after reintubation because of septic complications

Fig. 2

EIT images from three representative patients. Examples of EIT images from three representative patients, two succeeding (a, c) and one failing (b) the SBT. ∆EELI and the inhomogeneity index are shown at baseline, SBT_0 and SBT_30. For ∆EELI, the yellow and blue colour codes indicate EELI loss and increase, respectively. A pink scale code depicts inhomogeneity of gas distribution within the lungs. a Characterized by a relatively small ∆EELI, as referenced to baseline, at both SBT_0 (− 181 ml) and SBT_30 (− 178 ml). The inhomogeneity index is stable, ranging between 35 and 40 in all three trials. In b, conversely, ∆EELI is much greater (− 752 ml at SBT_0 and − 824 ml at SBT_30), indicating a remarkable loss of end-expiratory lung volume at both time points. The pink colour is quite scattered, indicating elevated values of inhomogeneity (54, 72 and 69, at baseline, SBT_0 and SBT_30, respectively). In c, ∆EELI does not significantly change (− 110 ml at SBT_0 and − 117 at SBT_30), while the inhomogeneity index is increased (68, 70 and 71 at baseline, SBT_0 and SBT_30, respectively). Notably, in contrast to the two previous examples, this patient was affected by chronic obstructive pulmonary disease