Obesity, PEEP and Postoperative Oxygenation

Study Overview
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Brief Summary
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A study on overweight patients undergoing anesthesia for laparoscopic surgery. - evaluation of positive end-expiratory pressure versus zero positive end-expiratory pressure during awakening on oxygenation in the early postoperative period.

Detailed Description
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Positive end-expiratory pressure (PEEP) is often used during mechanical ventilation to preserve end-expiratory lung volume. After emergence and extubation, this volume will diminish instantly. Some patients will have difficulties to restore functional residual capacity (FRC) during the early phase of recovery. If routine high FIO2 is being delivered together with maintained PEEP prior to extubation, several important prerequisites are established for the development of postoperative atelectasis. The investigators hypothesize that establishing zero positive end-expiratory pressure (ZEEP) immediately prior to emergence preoxygenation, will prevent gas with high oxygen concentration from entering dorso-basal areas of the lungs, and thereby diminishing postoperative atelectasis formation and improve oxygenation. This randomized controlled study will study overweight patients undergoing general anesthesia for laparoscopic surgery. The patients in the two study groups will receive mechanical ventilation with identical settings, comprising low TV, PEEP, and no RM. Randomization will occur at the end of surgery, before awakening. The patients will be allocated to zero PEEP (ZEEP) or maintained PEEP during emergence preoxygenation and extubation. Importantly, the intervention group will have ZEEP established while still having low ETO2 levels, prior to any preoxygenation. Arterial blood gases will be collected before, during and after anaesthesia. Primary endpoint measure will be change in oxygenation from before awakening to after awakening.

Official Title
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Zero Positive End-expiratory Pressure Before Emergence Improves Postoperative Oxygenation in Obese Patients Undergoing Laparoscopic Surgery - a Randomized Clinical Trial

Conditions
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Oxygenation

Intervention / Treatment
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* Procedure: ZEEP during awakening
* Procedure: PEEP during awakening


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Obese patients scheduled for elective laparocopic surgery. American Society of Anesthesiologists functional class I-III Body Mass Index 35-50 kg/m2 Exclusion Criteria: Body Mass Index ≥50 kg/m2 Peripheral oxygen saturation (SpO2) breathing air <94 % Symtomatic asthma, COPD or heart failure Ischemic heart disease Hemoglobin < 100g/l Smokers and ex-smokers that stopped smoking < 9 months ago Need for peroperative RM and PEEP higher than in study protocol, as indicated by SpO2 <92% despite the stipulated FiO2 0.30-0.35. Obstructive sleep apnea syndrome on home-CPAP

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 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: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: ZEEP during awakening<br>ZEEP will be used during emergence preoxygenation and awakening. | Procedure: ZEEP during awakening<br>* ZEEP will be established 2 min prior to the start of emergence preoxygenation and awakening.<br>|
| Active Comparator: PEEP during awakening<br>PEEP is maintained throughout emergence preoxygenation and awakening. | Procedure: PEEP during awakening<br>* PEEP will be maintained throughout emergence preoxygenation and awakening.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in oxygenation | Arterial blood samples will be collected for measurement of arterial oxygen partial pressure. | Bloodgases will be obtained 5 minutes before the start of the awakening procedure and 30 minutes after awakening and extubation. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Need for postoperative supplemental oxygen | Number of patients and amount of oxygen needed in the respective group postoperatively. | First 3 hours postoperatively. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Oxygenation, Positive end-expiratory pressure, General anaesthesia, Obesity, Atelectasis, Mechanical ventilation