Peroperative Use of Positive End-expiratory Pressure Prevents Formation of Atelectasis as Studied by Computerised Tomography at End of Surgery

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.

Study Overview

• Status: Completed
• Conditions: Atelectasis
• Intervention / Treatment: Procedure: Positive end-expiratory pressure; Procedure: Control group, zero PEEP

• Study Type: Interventional
• Enrollment (Actual): 24
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Sweden
  • Köping, Sweden
    • Region Västmanland

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 40 years to 75 years (ADULT, OLDER_ADULT)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

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).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: PREVENTION
• Allocation: RANDOMIZED
• Interventional Model: PARALLEL
• Masking: DOUBLE

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: PEEP group; Induction and maintenance of anaesthesia in a conventional manner. Peroperative ventilatory settings using positive end-expiratory pressure.	Procedure: Positive 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.
Active Comparator: Control group zero PEEP; Induction and maintenance of anaesthesia in a conventional manner. Peroperative ventilatory settings using zero end-expiratory pressure.	Procedure: Control 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	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.

Secondary Outcome Measures

Outcome Measure	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.
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.

Collaborators and Investigators

• Sponsor: Region Västmanland
• Investigators: Study Director: Lennart Edmark, Region Västmanland

Study record dates

Study Major Dates

• Study Start: November 1, 2015
• Primary Completion (Actual): November 1, 2016
• Study Completion (Actual): November 1, 2016

Study Registration Dates

• First Submitted: September 1, 2015
• First Submitted That Met QC Criteria: September 10, 2015
• First Posted (Estimate): September 14, 2015

Study Record Updates

• Last Update Posted (Actual): November 21, 2017
• Last Update Submitted That Met QC Criteria: November 19, 2017
• Last Verified: November 1, 2016

More Information

Terms related to this study

• Keywords: Computed tomography; Anaesthesia; Atelectasis; Oxygenation; Positive End-Expiratory Pressure
• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Lung Diseases; Pulmonary Atelectasis
• Other Study ID Numbers: Dnr 2015/338