Mechanical Ventilation and Respiratory Muscle Work of Breathing in Acute Respiratory Distress Syndrome (ARDS) Patients

Study Overview
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Brief Summary
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The purpose of this study is to demonstrate that mechanical ventilation guided by the diaphragm EMG signal (also know as neurally adjusted ventilatory assist [NAVA]) is superior compared to pressure support and pressure control ventilation.

Official Title
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The Role of Diaphragm Electromyography (EMG) Guided Mechanical Ventilation on Respiratory Physiology in Mechanically Ventilated Patients With Acute Respiratory Distress Syndrome (ARDS)

Conditions
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ARDS

Intervention / Treatment
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* Device: Mechanical ventilation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: intubated, mechanically ventilated patients meeting criteria for ARDS mean arterial blood pressure > 65 mmHg (with or w/o vasopressors) Exclusion Criteria: pregnancy increased intracranial pressure contra-indication naso-gastric tube diagnosed neuro-muscular disorder recent (<12 hours) use of muscle relaxants exclusion from sedation interruption protocol as used in our institution open chest or- abdomen very high inspiratory flow rate during supported ventilation inability to obtain informed consent

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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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Pressure support ventilation, ARDSnet<br>Mechanical ventilator is set to pressure support ventilation (6 ml/kg) for 30 min with positive end expiratory pressure (PEEP) set according to the higher arm of the ARDS network consensus. | Device: Mechanical ventilation<br>* The mechanical ventilator is set to different ventilation modes as described in the individual arms.<br>* Other names: Maquet Servo-i;|
| Active Comparator: Pressure control ventilation, ARDSnet<br>Mechanical ventilator is set to pressure control ventilation (6 ml/kg) for 30 min with PEEP set according to the higher arm of the ARDS network consensus. | Device: Mechanical ventilation<br>* The mechanical ventilator is set to different ventilation modes as described in the individual arms.<br>* Other names: Maquet Servo-i;|
| Active Comparator: Neurally adjusted ventilatory assist, ARDSnet<br>Mechanical ventilator is set to NAVA for 30 min with PEEP set according to the higher arm of the ARDS network consensus. | Device: Mechanical ventilation<br>* The mechanical ventilator is set to different ventilation modes as described in the individual arms.<br>* Other names: Maquet Servo-i;|
| Active Comparator: Neurally adjusted ventilatory assist, titrated<br>Mechanical ventilator is set to NAVA for 30 min with PEEP titrated using the diaphragm EMG signal. | Device: Mechanical ventilation<br>* The mechanical ventilator is set to different ventilation modes as described in the individual arms.<br>* Other names: Maquet Servo-i;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pressure-time product of the diaphragm | The pressure-time product of the transdiaphragmatic pressure (Pdi) during inspiration is obtained for each breath by multiplying the corresponding mean inspiratory Pdi signal above the end-expiratory baseline by the inspiration time. Breath-by-breath data are ensemble-averaged over the last 15 minutes of each study arm. | average of last 15 minutes of each study arm | 
| Patient - ventilator asynchrony index | Ventilator asynchrony is determined as the sum of the triggering and cycling-off delays per breath, expressed as a percentage of the total breath duration. The trigger delay is measured as the time difference between the onset of neural inspiration and the ventilator inspiratory flow, and the cycling delay as the time difference between the end of neural inspiration and the end of ventilator inspiratory flow. Breath-by-breath data are ensemble-averaged over the last 15 minutes of each study arm. | average of last 15 minutes of each study arm | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Transpulmonary pressure | Transpulmonary pressure is determined as the difference between mouth pressure and esophageal pressure during inspiration. Breath-by-breath data are ensemble-averaged over the last 15 minutes of each study arm. | average of last 15 minutes of each study arm | 
| Transdiaphragmatic pressure | Transdiaphragmatic pressure is determined as the difference between gastric pressure and esophageal pressure during inspiration. Breath-by-breath data are ensemble-averaged over the last 15 minutes of each study arm. | average of last 15 minutes of each study arm | 
| Oxygenation index | Oxygenation index is determined as the ratio between arterial oxygen tension and fraction of inspired oxygen. Arterial oxygen tension is obtained at the end of each study arm. | at the end of each study arm | 
| Dead space ventilation | Dead space ventilation is determined each breath using the Bohr equation: (PaCO2-PeCO2/PaCO2)*Vt. Here Vt is tidal volume, PaCO2 is the partial pressure of carbon dioxide in the arterial blood, and PeCO2 is the end-tidal carbon dioxide tension in the expired air. Breath-by-breath data are ensemble-averaged over the last 15 minutes of each study arm. | average of last 15 minutes of each study arm |