Lung Impedetiometric Modification in SBT and Extubation Failure

Electrical Impedance Tomography During Spontaneous Breathing Trial and Extubation Failure in Critically Ill Patients: an Observational Study

Weaning is the entire process aimed at liberating patients from mechanical ventilation and endotracheal intubation. Weaning should be considered as early as possible in order to reduce the time spent in invasive mechanical ventilation (iMV), which is associated with morbidity and mortality. To verify if patients are ready to be extubated, a spontaneous breathing trial (SBT) is performed. At this stage some clinical indices and objective parameters are evaluated, such as the breathing pattern, gas exchange, haemodynamic stability and patient's comfort. In case of SBT success, the patient can be extubated. However, a post-extubation respiratory failure can occur within the first 48 hours after extubation, thus making extubation unsuccessful. Some patients considered at risk for post-extubation respiratory failure benefit from the application of non-invasive ventilation (NIV) after extubation. Early characterization of these patients is crucial to improve their clinical outcomes.

Electrical Impedance Tomography (EIT) has been introduced in clinical practice as a non-invasive bedside monitoring tool to evaluate the aeration and ventilation of different lung regions. EIT has been proposed to guide ventilator settings adjustments in critically ill patients and to monitor prolonged weaning. However, the potential of EIT to assess SBT and after extubation in a general ICU population has never been evaluated insofar.

The present study aims to describe the modifications of lung aeration, ventilation and inhomogeneity occurring during SBT and after extubation in a general population of critically ill patients at the first SBT attempt.

Inclusion Criteria:

• Glasgow Coma Scale ≥8
• presence of clearly audible cough during suctioning with need for tracheal suctioning ≤2/hour
• normal sodium blood values
• core temperature <38.5° during the previous 8 hours
• Arterial partial pressure of oxygen to inspired oxygen fraction (PaO2/FiO2) ≥200 mmHg, with a Positive End Expiratory Pressure ≤5 cmH2O and FiO2 ≤0.4
• stable cardiovascular status (i.e., HR ≤140 beats/min, sBP between 90 and 160 mmHg without need for vasopressin, epinephrine or norepinephrine infusion, or with dopamine or dobutamine infusion ≤5 mcg/kg/min)
• cuff leak volume >110 mL

Exclusion Criteria:

• major heart arrhythmias or cardiac ischemia
• pneumothorax or emphysema
• recent (1 week) thoracic surgery
• presence of chest burns
• pregnancy
• inclusion in other research protocols