Résumé
Background: readiness for liberation from ventilatory support is evaluated with a spontaneous breathing trial (SBT) which assess the ability of a patient to sustain respiratory effort after extubation. Practices are heterogenous concerning the realization of the SBT, and there are few physiological studies on the topic. The objective of this study was to assess which SBT would best reproduce inspiratory effort to breathe after extubation.Material and method: this was a multicentric randomized cross-over physiological study, in a large population, in the era of modern intensive care unit (ICU) using the last generation of modern ventilators. Each included patient performed 3 SBTs of 15 min in random order: pressure support ventilation (PSV) level of 7 cmH2O with positive end expiratory pressure (PEEP) level of 0 cmH20 (PSV 7 PEEP 0), PSV 0 cmH2O with PEEP 0 cmH2O (PSV 0 PEEP 0), and T-piece trial (T-Piece). A rest period of baseline state ventilation was observed between the SBTs (10 min) and before extubation (30 min). Primary outcome was inspiratory muscle effort, reflected by the pressure time product per minute (PTPmin), calculated from esophageal pressure measurements at baseline state, before and after each SBTs, and 20 min after extubation.Results (median and interquartile range 25% -75%): planned interim analysis was performed after inclusion of 72 patients. Sixty-six were in final analysis, with five selected clinical phenotypes: 23 abdominal surgery, 10 brain injury, 7 chest trauma, 7 COPD and 19 miscellaneous (pneumonia, sepsis, heart disease). For all patients, the inspiratory effort after extubation calculated with PTPmin was 248 (189 - 329) cmH2O.s/min. The closest SBT was the T-Piece trial with 256 (184 - 344) cmH2O.s/min, versus 291 ± (219 - 359) cmH2O.s/min (p < 0.01) for PSV 0 PEEP 0 and 176 (116 - 264) cmH2O.s/min (p < 0.001) for PSV 7 PEEP 0. Nevertheless, these results differed according to clinical phenotypes. For brain injured patients and chest traumatized patients, PSV 0 PEEP 0 trial seemed to produce the effort closest to after extubation with respectively 208 (166 - 362) and 297 (265 - 361) cmH2O.s/min for the trial and 249 (195 - 354) and 281 (231 - 398) after extubation. PSV 7 PEEP 0 appeared to be the best trial for the COPD patients with 244 (218 - 279) cmH2O.s/min versus 267 (234 - 315) cmH2O.s/min after extubation.Conclusion: the main preliminary results of the present physiological randomized study suggest that the unassisted T-piece trial could be used for evaluating the after extubation effort to breathe in overall non selected patients. However, if we applied a more specific personalization of the SBT according to the clinical phenotype, it could be considered to use the unassisted PSV 0 PEEP 0 trial for brain injured patients and chest traumatized patients, and the assisted PSV 7 PEEP 0 trial for COPD patients.