Atelectasis
Conditions
Keywords
Atelectasis, Positive End-Expiratory Pressure, Oxygenation, Anaesthesia, Computed tomography
Brief summary
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.
Interventions
PROCEDUREPositive end-expiratory pressure
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.
PROCEDUREControl group, zero PEEP
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.
Sponsors
Region Västmanland
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
40 Years to 75 Years
Healthy volunteers
No
Inclusion criteria
* Healthy subjects, American Society of Anesthesiology (ASA) I-II. * Patients scheduled for non-abdominal day case surgery under general anaesthesia.
Exclusion criteria
* ASA class III or higher. * Body Mass Index (BMI) 30 or higher. * Arterial oxygen saturation (SpO2) \<96% breathing air. * Chronic Obstructive Pulmonary Disease (COPD). * Ischaemic heart disease. * Known or anticipated difficult airway. * Active smokers and ex-smokers with a history of more than 6 pack years. * Need for interscalene or supraclavicular plexus block for postoperative pain relief (risk of phrenic nerve paralysis).
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Area of atelectasis expressed as centimeter^2 | 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. | 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. |
| Measurement of aeras with different aeration in the particular CT 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. | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Oxygenation, oxygen tension in arterial blood expressed in kilo Pascal (kPa) | 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. | Arterial blood gas samples will be drawn and analyzed at the same time as the computed tomography scan will be undertaken. |
Countries
Sweden
Outcome results
None listed