Use of Pressure Muscle Index to Avoid Over-assistance During Pressure Support Ventilation

Study Overview
=================
Brief Summary
-----------------
Pressure support ventilation (PSV) is the most commonly used mode in mechanical ventilated patients. Studies have shown that over-assistance was prevalent in patients undergoing PSV. Up to now, no reliable method has been recommended to select an optimal inspiratory support level. Pressure muscle index (PMI) was introduced recently to evaluate the degree of spontaneous breathing effort. We hypothesize that PMI might be used as an indicator for over-assistance during PSV. In this randomized crossover study, inspiratory support is set at three levels according to negative, positive and zero PMI. Inspiratory effort, work of breathing, and respiratory mechanics are compared among the three inspiratory pressure support levels.

Official Title
-----------------
Use of Pressure Muscle Index to Avoid Over-assistance During Pressure Support Ventilation

Conditions
-----------------
Mechanical Ventilation

Intervention / Treatment
-----------------
* Procedure: Inspiratory support level


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Mechanical ventilated patients within 48 hours after the transition from a controlled mode to PSV Exclusion Criteria: History of neuromuscular disease History of diaphragm dysfunction and surgery History of esophageal, gastric or lung surgery Decreased level of consciousness Central respiratory drive dysfunction Considered withholding of life support

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Inspiratory support level with PMI equal to -2<br>PMI represents the difference between plateau airway pressure and peak airway pressure (plateau - peak) during an end-inspiratory airway occlusion. | Procedure: Inspiratory support level<br>* Inspiratory support is the pressure delivered by the ventilator during pressure support ventilation.<br>|
| Experimental: Inspiratory support level with PMI equal to 0<br>PMI represents the difference between plateau airway pressure and peak airway pressure (plateau - peak) during an end-inspiratory airway occlusion. | Procedure: Inspiratory support level<br>* Inspiratory support is the pressure delivered by the ventilator during pressure support ventilation.<br>|
| Experimental: Inspiratory support level with PMI equal to +2<br>PMI represents the difference between plateau airway pressure and peak airway pressure (plateau - peak) during an end-inspiratory airway occlusion. | Procedure: Inspiratory support level<br>* Inspiratory support is the pressure delivered by the ventilator during pressure support ventilation.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Inspiratory effort | Inspiratory effort is measured as pressure generated by inspiratory muscles using esophageal pressure monitoring. | 30 minutes | 
| Work of breathing | Work of breathing is measured by the Campbell diagram and pressure-time-product using esophageal pressure monitoring. | 30 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Respiratory system compliance (ml/cmH2O) | Respiratory system compliance is calculated as the ratio between tidal volume and driving pressure. | 30 minutes | 
| Partial pressure of oxygen in arterial blood (mmHg) | Partial pressure of oxygen in arterial blood is obtained by blood gas analysis. | Partial pressure of oxygen in arterial blood | 
| Partial pressure of carbon dioxide in arterial blood (mmHg) | Partial pressure of carbon dioxide in arterial blood is obtained by blood gas analysis. | 30 minutes | 
| Respiratory rate (breaths/min) | Respiratory rate calculation includes ineffective trigger. | 30 minutes | 
| Tidal volume (ml) | Tidal volume is obtained by intergation of flow-time tracing. | 30 minutes | 
| Rapid shallow breathing index | Rapid shallow breathing index is calculated as the ratio between respiratory rate and tidal volume. | 30 minutes | 
| The use of accessory respiratory muscle | The use of accessory respiratory muscle is observed at the bedside. | 30 minutes | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
mechanical ventilation, pressure support, inspiratory effort, work of breathing, lung injury