Effect of Positive End-expiratory Pressure on Optimal Balloon Volume During Esophageal Pressure Monitoring

Study Overview
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Brief Summary
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Esophageal pressure (PES), which has been used as a surrogate for pleural pressure. The volume of esophageal balloon can influence the accuracy of monitoring esophageal pressure. The optimal balloon volume is directly dependent on surrounding pressure. In the present study,the investigators will observe the optimal volume of esophageal balloon during the different PEEP in bench and clinical study.

Detailed Description
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The esophageal pressure (Pes) is used as a surrogate for pleural pressure to obtain transpulmonary pressure. Catheter with air balloon is the most commonly used method to measure the Pes. The optimal injected volume of the balloon is the key factor in accurate measurement of Pes. The recoil pressure of the balloon turns up while the balloon is over-filled, resulting in over-estimation of the PES; on the other hand, an under-filled balloon also cannot properly transmit the surrounding pressure of balloon. However, the researchers showed the optimal balloon volumes is related to the surrounding pressure and even is not correspond with manufacturer's recommendations. Theoretically, when balloon transmural pressure(PTM) is zero, representing the balloon in a condition with equivalent pressure inside and outside of the balloon, it was defined as optimal volume. However, in clinical settings, it is difficult to determine the balloon PTM, and therefore the optimal volume cannot be obtained, because the surrounding pressure of the balloon cannot be conveniently measured. In the present study, the investigators will develop a simple method to obtain the optimal balloon volume and observe the effect of positive end-expiratory pressure on optimal balloon volume during esophageal pressure monitoring. The investigators want to validate the accuracy of method in the bench study and clinical feasibility in mechanical ventilated patients.

Official Title
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Effect of Positive End-expiratory Pressure on Optimal Balloon Volume During Esophageal Pressure Monitoring in Mechanical Ventilated Patients: A Clinical Feasibility Study

Conditions
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Mechanical Ventilation

Intervention / Treatment
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* Procedure: Positive end-expiratory Pressure


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: postoperative patients with delayed emergence from general anesthesia admitted to the ICU for mechanical ventilation. Exclusion Criteria: age under 18 years; diagnosed or suspected esophageal varices; history of chronic obstructive pulmonary diseases or asthma; history of esophageal, gastric or lung surgery; evidence of active air leak from the lung, including bronchopleural fistula, pneumothorax, pneumomediastinum, or an existing chest tube; evidence of severe coagulopathy.

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 |
| --- | --- |
| Low PEEP group<br>The positive end-expiratory pressure was less than 10cmH2O | Procedure: Positive end-expiratory Pressure<br>* Positive end-expiratory pressure will be used during mechanical ventilation.<br>|
| High PEEP group<br>The positive end-expiratory pressure was higher or equal to 10cmH2O. | Procedure: Positive end-expiratory Pressure<br>* Positive end-expiratory pressure will be used during mechanical ventilation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The optimal balloon volume at different PEEP | The 3 minutes after esophageal balloon volume changing, the investigators will record the end-expiratory and end-inspiratory esophageal pressure. The pressure and volume curve will be drawn to determine the optimal volume. | within 3 minutes after esophageal balloon volume changing | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The transpulmonary pressure |  | within 3 minutes after esophageal balloon volume changing | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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optimal balloon volume, positive end-expiratory pressure