Lung Impedetiometric Modification in SBT and Extubation Failure

Study Overview
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Brief Summary
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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.

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

Conditions
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Weaning Failure, Mechanical Ventilation Complication

Intervention / Treatment
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* Diagnostic Test: Electrical Impedance Tomography (EIT)


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| SBT Success<br>Patients took part of this cohort when succeeding the Spontaneous Breathing Trial (SBT). | Diagnostic Test: Electrical Impedance Tomography (EIT)<br>* 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).<br>|
| SBT Failure<br>Patients took part of this cohort when failing the Spontaneous Breathing Trial (SBT). SBT Failure is defined by one or more of the following criteria occurring during the SBT: loss of ≥ 2 points of Glasgow Coma Scale respiratory rate/ tidal volume ≥105 breaths/min/L arterial partial pressure of oxygen ≤60 mmHg on inspired oxygen fraction (FiO2) ≥0.5 and/or pH <7.32 or a decrease in pH ≥0.07 units at the end of the SBT systolic Blood Pressure <90 mmHg or ≥180 mmHg or increased by ≥20% Heart Rate >140 beats/min or increased by 20% onset of major heart arrhythmias, or electrocardiographic signs of cardiac ischemia Respiratory Rate ≥35 breaths/min or increased by ≥50% increased effort, respiratory distress (as indicated by diaphoresis, accessory respiratory muscles recruitment, facial signs of distress and/or paradoxical breath) | Diagnostic Test: Electrical Impedance Tomography (EIT)<br>* 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).<br>|
| Extubation Success<br>Patients took part of this cohort when, after extubation, did not need continuous positive airways pressure (CPAP), non invasive ventilation (NIV) or reintubation within 48 hours. | Diagnostic Test: Electrical Impedance Tomography (EIT)<br>* 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).<br>|
| Extubation Failure<br>Need for continuous positive airways pressure (CPAP), non invasive ventilation (NIV) or reintubation within 48 hours from extubation, as defined by: Respiratory Rate >25 breaths/min for 2 hours Heart Rate >140 beats/min or sustained increase or decrease >20% clinical signs of respiratory muscle failure arterial partial pressure of oxygen (PaO2) <80 mmHg on inspired oxygen fraction (FiO2) ≥50% Arterial partial pressure of carbon dioxide >45 mmHg with pH <7.33 | Diagnostic Test: Electrical Impedance Tomography (EIT)<br>* 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).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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 | 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 | 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 | 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 | 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 | 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 | 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 | 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 | At 30 minutes after extubation (SB_30) | 
| Inhomogeneity Index (GI) at baseline | Inhomogeneity Index (GI) as assessed through electrical impedance tomography | At baseline during Pressure Support Ventilation | 
| Inhomogeneity Index (GI) after 5 minutes of the Spontaneous Breathing Trials (SBT_0) | Inhomogeneity Index (GI) as assessed through electrical impedance tomography | At 5 minutes of Spontaneous Breathing Trial (SBT_0) | 
| Inhomogeneity Index (GI) after 30 minutes of the Spontaneous Breathing Trials (SBT_30) | Inhomogeneity Index (GI) as assessed through electrical impedance tomography | At 30 minutes of Spontaneous Breathing Trial (SBT_30) | 
| Inhomogeneity Index (GI) after 5 minutes from extubation (SB_0) | Inhomogeneity Index (GI) as assessed through electrical impedance tomography | At 5 minutes after extubation (SB_0) | 
| Inhomogeneity Index (GI) after 30 minutes from extubation (SB_30) | Inhomogeneity Index (GI) as assessed through electrical impedance tomography | At 30 minutes after extubation (SB_30) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Arterial Blood Gases at baseline | Arterial Blood was sampled for gas analysis | At baseline during Pressure Support Ventilation | 
| Arterial Blood Gases at SBT_30 | Arterial Blood was sampled for gas analysis | At 30 minutes of Spontaneous Breathing Trial (SBT_30) | 
| Arterial Blood Gases at SB_30 | Arterial Blood was sampled for gas analysis | At 30 minutes after extubation (SB_30) | 
| the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) at baseline | the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) | At baseline during Pressure Support Ventilation | 
| the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) at 5 minutes of Spontaneous Breathing Trial (SBT_0) | the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) | At 5 minutes of Spontaneous Breathing Trial (SBT_0) | 
| the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) at SBT_30 | the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) | At 30 minutes of Spontaneous Breathing Trial (SBT_30) | 
| the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) at 5 minutes after extubation (SB_0) | the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) | At 5 minutes after extubation (SB_0) | 
| the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) at 30 minutes after extubation (SB_30) | the ratio between respiratory rate (RR) and tidal volume (Vt) (RR/Vt) | At 30 minutes after extubation (SB_30) |