Decreasing Trigger Sensitivity Could Assist PEEP to Further Improve Regional Ventilation Distribution

Study Overview
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Brief Summary
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In mechanically ventilated patients during supine position, alveolar collapse usually distributes in dependent lung region.Decrease of flow trigger sensitivity might improve homogeneous of tidal volume distribution.

Detailed Description
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In mechanically ventilated patients during supine position, alveolar collapse usually distributes in dependent lung region. High positive end expiratory pressure (PEEP) has been applied to improve the homogeneous distribution of ventilation by increasing the end expiratory lung ventilation (EELV) and alveolar recruitment. However, for patients who increasing PEEP in some extent still existed poor aeration in the dependent region, further elevating PEEP seems to be unreasonable that perhaps lead to overdistension. Decreasing trigger sensitivity might further evoke inspiratory efforts to improve the ventilation for this type of patients.The Electrical impedance tomography (EIT) was applied in monitoring the regional ventilation distribution at the bedside.

Official Title
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Decreasing Trigger Sensitivity Could Assist PEEP to Further Improve Regional Aeration and Homogeneity During Pressure Assist Ventilation: A Preliminarily Physiological Study

Conditions
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Mechanical Ventilation

Intervention / Treatment
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* Procedure: flow trigger


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: The post operative patients who received pressure support ventilation; After the clinical PEEP was evaluated 5cmH2O, the tidal volume distribution still existed heterogeneity. Exclusion Criteria: Under 18 years; History of diaphragm dysfunction and surgery; Central respiratory drive dysfunction; history of esophageal, gastric or lung surgery; The contraindication of using EIT (pacemaker, defibrillator, and implantable pumps).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 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 |
| --- | --- |
| the lowest trigger sensitivity<br>The flow trigger of ventilator was set as the lowest level of sensitivity. | Procedure: flow trigger<br>* The flow trigger will be adjust during the pressure assist ventilation.<br>|
| the highest trigger sensitivity<br>The flow trigger of ventilator was set as the highest level of sensitivity. | Procedure: flow trigger<br>* The flow trigger will be adjust during the pressure assist ventilation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The homogeneity of distribution of tidal volume | EIT was used to monitoring the homogeneity of distribution of tidal volume that was divided into two contiguous regions of interest (ROI) equally, the dependent and non-dependent area. The ratio of relative distribution of tidal ventilation of two ROI was calculated. | within 20 minutes after changing flow trigger | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in global and regional EELV | The change of EELV was measured after changing flow trigger based on the baseline level. | within 20 minutes after changing flow trigger |