Esophageal Pressure Measurements During One-lung Ventilation

Study Overview
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Brief Summary
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The investigators will assess the feasibility and validity of esophageal pressure measurements during one-lung ventilation in the lateral position for surgery by comparing to lung collapse estimated from electrical impedance tomography during a PEEP trial.

Detailed Description
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In this prospective cohort study, the investigators will assess the feasibility of esophageal pressure measurements during general anesthesia with one-lung ventilation in patients undergoing non-cardiac intrathoracic surgery, which is typically conducted in the lateral position. The investigators will measure esophageal pressure with an esophageal balloon catheter. The investigators will compare esophageal pressure measurements to lung collapse estimated by Electrical Impedance Tomography (EIT). Patients will be equipped with the EIT belt before induction of anesthesia, and a one-minute EIT recording during spontaneous breathing will be conducted. Anesthesia will be induced as to institutional standards and upon the discretion of the attending anesthesiologist. After placement of a double-lumen endotracheal tube, the esophageal balloon catheter will be placed. After placement of the esophageal catheter, esophageal pressure, transpulmonary pressure, airway pressure and flow and EIT signal will be recorded (baseline). When the patient has been positioned for surgery (typically in the lateral position), a second recording of the above parameters is conducted (lateral). One-lung ventilation will then be initiated and a third measurement (OLV) is made. During the third measurement, a decremental positive end-expiratory pressure trial will be conducted to correlate the measured esophageal pressure to the positive end-expiratory pressure where lung collapse is detected from EIT. Before surgery, the EIT belt is opened and removed from the surgical field to avoid interference. If feasible, when surgery is finished, before reversal of neuromuscular blockade and extubation, a final recording of EIT, esophageal pressure, transpulmonary pressure, airway pressure and flow will be conducted.

Official Title
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An Observational Study to Determine Feasibility and Validity of Esophageal and Transpulmonary Pressure Measurements During One Lung Ventilation

Conditions
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Surgery, One-lung Ventilation

Intervention / Treatment
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* Other: One-lung ventilation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: adult patients undergoing non-cardiac surgery with OLV Exclusion Criteria: COPD Active respiratory infection Prior lung resection Prior esophageal/gastric surgery Esophageal varices Patients under effective anticoagulation at time of surgery Pacemaker/ICD Pregnancy Inability to give written 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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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: One-lung ventilation|One-lung ventilation as part of routine clinical care for patients undergoing thoracic surgery under general anesthesia|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Esophageal pressure at lung collapse | Esophageal pressure during one-lung ventilation in the lateral position at beginning lung collapse as measured by electrical impedance tomography during a decremental PEEP titration | During one-lung ventilation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Esophageal Pressure | Esophageal Pressure during one-lung ventilation in the lateral position at airway closure as assessed by pressure-volume curves | During one-lung ventilation | 
| Esophageal Pressure | Esophageal Pressure during two-lung ventilation in the lateral position at airway closure as assessed by pressure-volume curves | During two-lung ventilation in the lateral position | 
| Esophageal Pressure | Esophageal Pressure during two-lung ventilation in the supine position at airway closure as assessed by pressure-volume curves | During two-lung ventilation in the supine position | 
| Optimum PEEP | PEEP during PEEP titration that provides optimum trade-off between lung collapse and overdistension, as measured by Electrical Impedance Tomography | During one-lung ventilation | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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One-lung ventilation, Electrical Impedance Tomography, Thoracic Surgery, Esophageal manometry, Transpulmonary Pressure, Lung-protective ventilation