Oxygenation Test During General Anesthesia

Study Overview
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Brief Summary
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The study investigates if applying a special ventilatory strategy during anesthesia for laparoscopic gastric by pass, produces less atelectasis and better oxygenation in spite of using 100 % oxygen during pre oxygenation and induction of anesthesia. The study investigates oxygenation with blood gas samples but also with a new method that might give more information without the use of blood gas samples. Primary: Oxygenation in patients with morbid obesity improves if preoxygenation, induction and maintenance of anesthesia is performed with either a continuous positive airway pressure (CPAP) or a positive end expiratory pressure (PEEP), respectively, of 10 cm H2O, in comparison to a technique without CPAP but with a PEEP of 10 cm H2O. Secondary: The improved oxygenation during anesthesia can be prolonged inte the postoperative period if emergence from anesthesia is performed without high levels of oxygen.

Official Title
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Application of Protective Ventilation Improves Oxygenation During and After Anesthesia. Is it Possible That a Special Procedure, an Oxygenation Test, Can Replace Arterial Blood Gases When Evaluating Oxygenation?

Conditions
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Morbid Obesity

Intervention / Treatment
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* Procedure: CPAP and 100% oxygen
* Procedure: CPAP and 31% oxygen
* Procedure: No CPAP and 100% oxygen


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adult patients scheduled for elective surgery of Morbid Obesity. ASA 1-2. (ASA = American Society of Anesthesiologists classification). Body mass index (BMI) ≥ 35 but < 50 Exclusion Criteria: ASA 3 Anticipated difficult intubation. Major bleeding. Problems with ventilation necessitating protocol aberrations. Obstructive sleep apnea syndrome with CPAP treatment at home. Angina Pectoris

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 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: Factorial Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Start O2 100% and CPAP 10, end O2 100%.<br>This arm describes some aspects of ventilation during anesthesia for laparoscopic gastric bypass. Pre-oxygenation is with an inspiratory oxygen fraction(FIO2) of 1.0, supplied by a continuous positive airway pressure of 10 centimeters of water(cmH2O), during anesthesia a positive end-expiratory pressure of 10 cmH2O is used and during emergence from anesthesia a FIO2 of 1.0 is used. The intervention associated with this arm is labeled CPAP and 100% oxygen. | Procedure: CPAP and 100% oxygen<br>* During pre oxygenation and induction of anesthesia 100 % oxygen is used with a continuous positive airway pressure of 10 cmH2O, during maintenance of anesthesia a positive endexpiratory pressure of 10 cm H20 is used with controlled volume ventilation aiming at an end tidal carbon dioxide (CO2) level of 5 %. During emergence from anesthesia 100 % oxygen is used.<br>* Other names: Preventive ventilation;|
| Experimental: Start O2 100% and CPAP 10, end O2 31%.<br>This arm describes some aspects of ventilation during anesthesia for laparoscopic gastric bypass. Pre-oxygenation is with a FIO2 of 1.0, supplied by a continuous positive airway pressure of 10 cmH2O, during anesthesia a positive end-expiratory pressure of 10 cmH2O is used and during emergence from anesthesia a FIO2 of 0.3 is used. The intervention associated with this arm is labeled CPAP and 31% oxygen. | Procedure: CPAP and 31% oxygen<br>* During pre oxygenation and induction of anesthesia 100 % oxygen is used with a continuous positive airway pressure of 10 cm H2O, during maintenance of anesthesia a positive endexpiratory pressure of 10 cm H20 is used with controlled volume ventilation aiming at an end tidal CO2 level of 5 %. During emergence from anesthesia 31 % inspiratory oxygen or the inspiratory oxygen level needed to achieve a SpO2 of at least 96 % (if 31 % oxygen is not enough), is used.<br>* Other names: Preventive ventilation;|
| Experimental: Start O2 100% and CPAP 0, end O2 100%.<br>This arm describes some aspects of ventilation during anesthesia for laparoscopic gastric bypass. Pre-oxygenation is with a FIO2 of 1.0, without a continuous positive airway pressure, during anesthesia a positive end-expiratory pressure of 10 cmH2O is used and during emergence from anesthesia a FIO2 of 1.0 is used. The intervention associated with this arm is labeled No CPAP and 100% oxygen. | Procedure: No CPAP and 100% oxygen<br>* This intervention follows a standard protocol without the use CPAP during induction of anesthesia.<br>* Other names: Standard protocol.;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in peripheral O2 saturation(SpO2)during and 1 hour after anesthesia in comparison to awake before anesthesia. | During anesthesia SpO2 is measured at three different levels of oxygen; 21, 26 and 31 % respectively as long as SpO2 does not go lower than 87 % and compared to SpO2 immediately before anesthesia. SpO2 breathing air one hour after anesthesia is compared to SpO2 before anesthesia. | Change in SpO2 from 5 min before start of anesthesia, to 5 min after intubation, 5 min before extubation and 1 hour after extubation. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Arterial blood gas values for saturation (SaO2) | During anesthesia SaO2 is measured at three different levels of oxygen; 21, 26 and 31 % respectively as long as SpO2 (sic! does not go lower than 87 % and compared to SaO2 immediately before anesthesia. SaO2 breathing air one hour after anesthesia is compared to SaO2 before anesthesia. | 5 min before anesthesia, 5 min after intubation, 5 min before extubation and 1 hour after anesthesia. | 
| Arterial oxygen tension (PaO2) | During anesthesia PaO2 is measured at three different levels of oxygen; 21, 26 and 31 % respectively as long as SpO2 (sic) does not go lower than 87 % and compared to PaO2 immediately before anesthesia. PaO2 breathing air one hour after anesthesia is compared to PaO2 before anesthesia. | 5 min before start of anesthesia, 5 min after intubation, 5 min before extubation and 1 hour after extubation. |