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Atelectasis is common during and after general anaesthesia and a number of interventions have been suggested in order to prevent their formation. The use of Positive End Expiratory Pressure (PEEP) during general anaesthesia has in recent years been questioned.
The investigators hypothesize that the use of PEEP as a single intervention improves oxygenation and prevents atelectasis as investigated by computed tomography compared to a control group with zero PEEP.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| PEEP group | Active Comparator | Induction and maintenance of anaesthesia in a conventional manner. Peroperative ventilatory settings using positive end-expiratory pressure. |
|
| Control group zero PEEP | Active Comparator | Induction and maintenance of anaesthesia in a conventional manner. Peroperative ventilatory settings using zero end-expiratory pressure. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Positive end-expiratory pressure | Procedure | Induction of anaesthesia is performed in a conventional manner using a target controlled infusion of propofol and remifentanil. Intubation of the trachea is facilitated by rocuronium. As soon as correct position of the endotracheal tube is confirmed, controlled ventilation is started with a tidal volume of 7 mL/kg body weight and a respiratory frequency of 10. The fresh gas flow is set to 1 litre/min with an oxygen mixture of 40%, aiming for an inspired oxygen fraction (FiO2) of 30-35%. Positive end-expiratory pressure is set to 6 or 8 cm H20 (8 if BMI>25) in the intervention group. Unless the patient´s SpO2 falls below 90%, the FiO2 remains unchanged throughout the procedure. |
| Measure | Description | Time Frame |
|---|---|---|
| Area of atelectasis expressed as centimeter^2 | The area of atelectasis in the lungs is assessed by computed tomography (CT) 5-10 mm above the dome of the right diaphragm and expressed in centimeter^2 and as a percentage of the total lung area in the particular scan. | Within 1-2 hours, just before emergence from anesthesia.The outcome measure (atelectasis) will be investigated at just one point i.e. end of surgery but before emergence from anaesthesia. |
| Measurement of aeras with different aeration in the particular CT scan. | The areas of different aeration are assessed by computed tomography (CT) 5-10 mm above the dome of the right diaphragm and expressed in centimeter^2 and as a percentage of the total lung area in the particular scan. | Within 1-2 hours, just before emergence from anesthesia.The outcome measure (atelectasis) will be investigated at just one point i.e. end of surgery but before emergence from anaesthesia. |
| Measure | Description | Time Frame |
|---|---|---|
| Oxygenation, oxygen tension in arterial blood expressed in kilo Pascal (kPa) | Arterial blood gas samples will be drawn and analyzed at the same time as the computed tomography scan will be undertaken. | Within 1-2 hours, just before emergence from anesthesia. At end of surgery but before emergence from anaesthesia, at the same time as the lungs are investigated by computed tomography. |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Lennart Edmark | Region Västmanland | Study Director |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Region Västmanland | Köping | Sweden |
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|
| Control group, zero PEEP | Procedure | Induction of anaesthesia is performed in a conventional manner using a target controlled infusion of propofol and remifentanil. Intubation of the trachea is facilitated by rocuronium. As soon as correct position of the endotracheal tube is confirmed, controlled ventilation is started with a tidal volume of 7 mL/kg body weight and a respiratory frequency of 10. The fresh gas flow is set to 1 litre/min with an oxygen mixture of 40%, aiming for an inspired oxygen fraction (FiO2) of 30-35%. Zero PEEP is used. Unless the patient´s SpO2 falls below 90%, the FiO2 remains unchanged throughout the procedure. |
|
| Oxygenation, oxygen tension in arterial blood expressed in kilo Pascal (kPa) | Arterial blood gas samples will be drawn and analyzed 15 minutes after emergence from anesthesia and extubation. | Within 2 hours perioperatively, 15 minutes after extubation. |
| ID | Term |
|---|---|
| D001261 | Pulmonary Atelectasis |
| ID | Term |
|---|---|
| D008171 | Lung Diseases |
| D012140 | Respiratory Tract Diseases |
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| ID | Term |
|---|---|
| D011175 | Positive-Pressure Respiration |
| D035061 | Control Groups |
| ID | Term |
|---|---|
| D012121 | Respiration, Artificial |
| D058109 | Airway Management |
| D013812 | Therapeutics |
| D012138 | Respiratory Therapy |
| D015340 | Epidemiologic Research Design |
| D004812 | Epidemiologic Methods |
| D008919 | Investigative Techniques |
| D012107 | Research Design |
| D008722 | Methods |
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