Regional Distribution Differences Between Neurally Adjusted Ventilatory Assist and Pressure Support Ventilation

Study Overview
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Brief Summary
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Neurally adjusted ventilatory assist (NAVA) is an FDA approved mode of mechanical ventilation. This mode of ventilation is currently in routine use in adult, pediatric and neonatal intensive care units. The electrical activity of the diaphragm, the largest muscle used during inspiration, is measured. The ventilator triggers (synchronizes patient effort) and applies proportional assistance based on measured electrical activity of the diaphragm (Edi). This electrical activity is measured through a feeding tube that also has a multiple-array esophageal electrode in it. This mode of ventilation has been proven to be equivalent to pressure support ventilation (PSV). Theoretically, the breath-to-breath control offered by NAVA may not only trigger faster and synchronize better, but provide the support deemed appropriate by the central nervous center on demand. Traditionally in the intensive care unit (ICU), pressure support is applied to subject breathing spontaneously. Pressure is set to achieve a given tidal volume. The influence of changing lung compliance not only from the lung disease itself, but the interactions of the respiratory muscles can drastically change minute ventilation and contribute to hyper- or hypoventilation. These changes are typically found on assessment of end-tidal carbon dioxide (CO2), blood gas, or oxygen saturation (SpO2) monitoring; all of which are potentially preventable if we allowed the central nervous system to control the ventilator. NAVA may allow us to couple the central nervous system (neuro-coupling) with the ventilator to provide real-time proportional assistance, reduce work of breathing and apply physiologic breathing patterns.

Official Title
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Regional Distribution Differences Between Neurally Adjusted Ventilatory Assist and Pressure Support Ventilation

Conditions
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Respiratory Failure

Intervention / Treatment
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* Device: Neurally Adjusted Ventilatory Assist (NAVA)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All intubated and mechanically ventilated patients in our intensive care units (ICUs) will be screened for the following inclusion criteria: Age: 1 month to 18 years. Mechanically ventilated for longer than 6 hours Either: Eligible for a spontaneous breathing mode of ventilation (not receiving chemical paralytics and has an appropriate spontaneous respiratory drive/rate given the size and condition of the patient) as determined by the team. or Currently in the pressure support ventilation (PSV) or neurally adjusted ventilatory assist (NAVA) mode of ventilation Exclusion Criteria: Patients in which a nasal gastric or oral gastric tube is contraindicated. Examples are but not limited to: s/p esophagus, tracheal surgery, bleeding disorders, facial trauma. Uncuffed endotracheal tube (ETT) Cervical-spine injury that prohibits rolling the patient for electrical impedance tomography (EIT) band placement. Difficult airway Congenital cyanotic heart defects Positive end expiratory pressure (PEEP) > 15 cmH2O Fractional inspired oxygen concentration (FIO2) > 0.8 Peak inspiratory pressure (PIP) > 30 cmH2O Patients who are receiving chemical paralysis History of prematurity (birth at post-conceptual age <37 weeks)

Ages Eligible for Study
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Minimum Age: 1 Month
Maximum 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 |
| --- | --- |
| NAVA-PSV<br>Subject will receive 4 hours of NAVA followed by 4 hours of PSV. | Device: Neurally Adjusted Ventilatory Assist (NAVA)<br>* Subjects will be placed in the NAVA mode of ventilation.<br>|
| PSV-NAVA<br>Subject will receive 4 hours of PSV followed by 4 hours of NAVA. | Device: Neurally Adjusted Ventilatory Assist (NAVA)<br>* Subjects will be placed in the NAVA mode of ventilation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Regional distribution difference measured by electrical impedence tomography (EIT) | Regional distribution difference measured by EIT. Area and upper to lower lung volume ratios (as determined with EIT) will be the primary data analyzed. Global and regional filling of the lung will be compared during pressure support ventilation and neurally adjusted ventilatory assist. | Change from baseline regional distribution of ventilation after the 4th hour and after 8th hour | 
| Oxygen and metabolic cost of breathing | Oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ), and Work of breathing (VO2/time) will be measured and compared between baseline, pressure support ventilation (PSV), and neurally adjusted ventilatory assist (NAVA) within each patient. Percent change will be compared between control (PSV) and NAVA group. | Change from baseline oxygen cost of breathing and carbon dioxide production after the 4th hour and after the 8th hour | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Oxygenation | Oxygen saturation measured by pulse oxymetry (SpO2), SpO2/FiO2 ratio, non-invasive oxygen content (SpOC), and frequency of desaturations will be recorded continuously and compared between pressure support ventilation (PSV) and neurally adjusted ventilatory assist (NAVA). Although not a primary outcome measure of this study, oxygenation will allow us to further determine the safety of NAVA compared to PSV. | Monitored/recorded continuously for duration of study (8 hours total) | 
| Lung mechanics | Compliance, peak inspiratory pressures, positive end expiratory pressure, tidal volumes, inspired oxygen concentration, electrical activity of the diaphragm (Edi), specific Edi (ratio of tidal volume to Edi), will be measured in each patient during pressure support ventilation and neurally adjusted ventilatory assist. | Monitored/recorded every 30 seconds for duration of study (8 hours total) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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NAVA, neurally adjusted ventilatory support, lung injury, ventilation, lung volume distribution, oxygen cost of breathing