Lung Impedetiometric Modification in SBT and Extubation Failure

University Magna Graecia80 enrolled

Overview

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.

Study Type

OBSERVATIONAL

Enrollment

Conditions

Weaning Failure Mechanical Ventilation Complication

Electrical Impedance Tomography (EIT)DIAGNOSTIC_TEST

After enrollment, a silicon EIT belt of proper size with 16 electrodes was placed around the patient's chest between the 4th and 6th intercostal spaces, and connected to the EIT device. All patients were ventilated in Pressure Support Ventilation (PSV) mode, with a dedicated ventilator connected to the EIT device. We acquired 5-min EIT data records at baseline (during PSV), during the first (SBT\_0) and the last (SBT\_30) 5 minutes of SBT, and, when the patient was extubated, during spontaneous breathing soon after (SB\_0) and 30 minutes after extubation (SB\_30). EIT and ventilator data were recorded at a sample of 20 Hz. The last 3 minutes of each record were analyzed. We measured respiratory rate (RR); Vt changes from baseline, expressed as percent (dVt%); dEELI variations from baseline, expressed in mL; the Global Inhomogeneity index (GI); Impedance ratio (IR) and the Center of Ventilation (CoV).

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Change of end-expiratory lung impedance (dEELI) from baseline at first 5 minute of Spontaneous Breathing Trial (SBT_0)

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At 5 minutes of Spontaneous Breathing Trial (SBT)

Change of end-expiratory lung impedance (dEELI) from baseline at last 5 minute of Spontaneous Breathing Trial (SBT_30)

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At the last 5 minutes of Spontaneous Breathing Trial (SBT)

Change of end-expiratory lung impedance (dEELI) from baseline at first 5 minute after extubation (SB_0)

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At 5 minutes after extubation

Change of end-expiratory lung impedance (dEELI) from baseline at last 30 minute after extubation (SB_30)

change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At 30 minutes after extubation

Change of tidal volume in percentage (dVt%) from baseline at last 5 minute of SBT (SBT_0)

change from baseline, expressed in percentage, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At 5 minutes of spontaneous breathing trial (SBT_0)

Change of tidal volume in percentage (dVt%) from baseline from baseline at 30 minute of Spontaneous Breathing Trial (SBT_30)

change from baseline, expressed in percentage, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At the last 5 minutes of Spontaneous Breathing Trial (SBT) (SBT_30)

Change of tidal volume in percentage (dVt%) from baseline after 5 minutes from extubation (SB_0)

change from baseline, expressed in percentage, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At 5 minutes after extubation (SB_0)

Change of tidal volume in percentage (dVt%) from baseline at last 30 minute after extubation (SB_30)

change from baseline, expressed in percentage, of the end expiratory lung volume as assessed through electrical impedance tomography

Time frame: At 30 minutes after extubation (SB_30)

Inhomogeneity Index (GI) at baseline