Individualized vs Low PEEP in One Lung Ventilation

Study Overview
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Brief Summary
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The aim of the prospective crossover study is to investigate the effect of individualized positive end-expiratory pressure (PEEP) on measures of tissue oxygenation, compared with low PEEP.

Detailed Description
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During surgery on the lung, ventilation of one lung at a time is often necessary. During thoracic surgery requiring one-lung ventilation (OLV), hypoxemia (reduced oxygen tension in blood) can present a clinical challenge. Due to multiple factors, the likelihood of hypoxemia during OLV in obese patients is increased. Atelectasis (collapse of the lung airspaces) contributes to hypoxemia and can be mitigated by application of recruitment maneuvers and positive end-expiratory pressure (PEEP). A recruitment maneuver is a breath given in a mechanically ventilated patient that helps to open up collapsed air spaces, and PEEP is application of a continuous amount of positive pressure that helps keep the air spaces open at the end of an exhaled breath. Adjusting the level of PEEP to each individual patient's optimal lung compliance (individualized PEEP) improves blood oxygen levels compared to application of standard low PEEP (5 cmH2O); however, higher levels of PEEP required to achieve optimal lung compliance could increase intrathoracic pressures to a level that impedes normal circulation. This could negatively affect blood flow (cardiac output) and delivery of oxgyen to vital organs. Evidence addressing OLV in obese patients is lacking. The purpose of this study is to compare brain oxygen levels (cerebral oxygen saturation) and measures of blood flow and gas exchange during OLV with individualized PEEP vs low standard PEEP in obese patients undergoing thoracic surgery. To our knowledge, there is no previous study that compares oxygen delivery to vital organs (such as the brain) during OLV using individualized PEEP versus standard low PEEP, in an obese patient population. In this study, subjects undergoing OLV during surgery to remove a portion of the lung (lobectomy) will undergo a process to determine their individualized PEEP and then two 20-minute experimental periods-- one period with OLV with low PEEP and one period with OLV with individualized PEEP. Measurements of cerebral oxygen saturation, blood oxygen levels, cardiac output, and blood pressure medication dose will be measuring before and after these experimental periods during surgery.

Official Title
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The Effect of Individualized PEEP Compared to Low PEEP on Tissue Oxygenation During One Lung Ventilation in Obese Patients Undergoing Thoracic Surgery

Conditions
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One-Lung Ventilation, Obesity, Lung Diseases

Intervention / Treatment
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* Procedure: One-lung ventilation with individualized PEEP
* Procedure: One-lung ventilation with low PEEP


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subject undergoing elective pulmonary lobectomy requiring one-lung ventilation Body-mass index ≥ 30 kg/m2 Age ≥ 18 years and ≤ 80 years Exclusion Criteria: Age ≤ 18 year or ≥ 80 years Moderate or severe cardiac valvular disease Left ventricular ejection fraction < 30% Moderate or severe right ventricular systolic dysfunction Severe pulmonary hypertension Presence of pulmonary bullae or blebs on preoperative chest imaging studies (e.g., radiograph, computed tomograph) Emergency surgery Previous history of lung surgery on the non-operative lung Pregnancy Incarceration Mental incapacitation Patient refusal Non-English speaking

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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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Mechanical ventilation with individualized PEEP will be compared to mechanical ventilating with low PEEP during lung isolation in each subject. Each subject will receive one PEEP level then will receive the second PEEP level. The order in which each subject receives the PEEP level will be randomized.
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Individualized PEEP<br>Individualized PEEP will be identified by performing a decremental PEEP protocol which will determine the level of PEEP that correlates with maximal lung compliance in each subject. Subjects will receive one-lung ventilation with individualized PEEP | Procedure: One-lung ventilation with individualized PEEP<br>* During one-lung ventilation for lung resection surgery, PEEP will be applied. After a subject's individualized PEEP (PEEP that corresponds to maximum lung compliance) is determined, the subject will receive one-lung ventilation with individualized PEEP.<br>|
| Active Comparator: Low PEEP<br>Subjects will receive One-lung ventilation with low PEEP (5 cmH2O) | Procedure: One-lung ventilation with low PEEP<br>* Subjects will receive one-lung ventilation with low PEEP (5 cmH2O)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cerebral oximetry | Cerebral oximetry (a measure of oxygen levels in the brain) as measured by near-infrared spectroscopy (noninvasive monitor applied to the forehead) | Change from baseline cerebral oximetry at the end of each intraoperative 20 minute experimental period. All measurements are made during the 4-6 hour surgery. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Arterial blood oxygen tension (PaO2) | A measure of oxygen level in arterial blood | Measured at baseline, and then at the end of each 20 minute intraoperative experimental period. All measurements are made during the 4-6 hour surgery. | 
| Venous blood oxygen tension (PvO2) | A measure of oxygen level in venous blood | Measured at baseline, and then at the end of each 20 minute intraoperative experimental period. All measurements are made during the 4-6 hour surgery. | 
| Venous blood oxygen saturation (SvO2) | A measure of oxygen saturation in venous blood | Measured at baseline, and then at the end of each 20 minute intraoperative experimental period. All measurements are made during the 4-6 hour surgery. | 
| Cardiac output | A measure of blood flow throughout the body | Measured at baseline, and then at the end of each 20 minute intraoperative experimental period. All measurements are made during the 4-6 hour surgery. | 
| Phenylephrine dose | Total dose of phenylephrine (medication used to raise blood pressure) | Total dose of phenylephrine administered during each intraoperative 20 minute experimental period. All measurements are made during the 4-6 hour surgery. |