Electrical impedance tomography monitoring during spontaneous breathing trial: Physiological description and potential clinical utility.

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 behavior 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 submitted 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.

What is the future of acute respiratory distress syndrome after the Berlin definition?

PURPOSE OF REVIEW: To analyze recently published articles in the medical literature that studied distinct aspects of adult patients with acute respiratory distress syndrome (ARDS) after the new Berlin definition introduced in 2012. RECENT FINDINGS: The degree of ARDS severity according to this new classification correlated well with extravascular lung water index, pulmonary vascular permeability index and the finding of diffuse alveolar damage on autopsy. The new possibility of bedside echocardiographic evaluation of biventricular cardiac function is indicating the necessity of including a subgroup of severity of patients with right ventricular dysfunction. High-resolution CT evaluation showed that signs of pulmonary fibroproliferation in early ARDS predict increased ventilator dependency, multiple organ failure and mortality. The median development of ARDS 1 or 2 days after hospital admission emphasizes the need for ARDS intrahospital prevention, especially protective ventilation in non-ARDS patients. The better outcome with the use of prone position in patients with PaO2/FIO2 below 150 recently observed questioned the Berlin definition thresholds to decide the future best treatment strategies according to the proposed degree of severity of the syndrome. SUMMARY: The impact of the Berlin definition of ARDS on the incidence, better treatment stratification and mortality ratio of ARDS is still to be determined.