Zero Positive End-expiratory Pressure Before Emergence Prevents Postoperative Atelectasis.

Zero Positive End-expiratory Pressure Applied Before Emergence Preoxygenation Prevents Postoperative Atelectasis - a Randomized Controlled Trial.

A study on healthy patients undergoing anesthesia for non-abdominal surgery - evaluation of positive end-expiratory pressure versus zero positive end-expiratory pressure on the amount of atelectasis in the early postoperative period.

Study Overview

• Status: Completed
• Conditions: Atelectasis; Oxygenation
• Intervention / Treatment: Procedure: ZEEP; Procedure: PEEP

Detailed Description

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 has been 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 prevent postoperative atelectasis formation.

This randomized controlled study will study patients undergoing non-abdominal day case surgeries under general anesthesia. The patients in the two study groups will receive mechanical ventilation with identical settings, comprising low TV, moderate PEEP, and no RM. At the end of surgery, the lungs will be examined by CT, and any atelectasis areas will be calculated. Randomization will occur after the first CT. 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. The study subjects will be examined with CT no.2 approximately thirty min after extubation. Primary endpoint measure will be atelectasis area as a percentage of total lung area. Blood gases will be collected for comparison of oxygenation as a secondary outcome measure.

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Sweden
  • Köping, Sweden
    • Department of Anaesthesia and Intensive Care

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:

• American Society of Anesthesiology (ASA) class I-II
• Non-abdominal day case surgery under general anesthesia

Exclusion Criteria:

• Body mass index (BMI) ≥30 kg/m2
• Arterial oxygen saturation (SpO2) breathing air <95 %
• Chronic Obstructive Pulmonary Disease (COPD) or symptomatic asthma
• Symptomatic congestive heart failure
• Ischemic heart disease
• Hemoglobin <100 g/L
• Active smokers
• 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 Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: ZEEP at awakening; Controlled ventilation with tidal volume of 7 mL/kg of ideal body weight and respiratory frequency 10. 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 (PEEP) is set to 7 or 9 cm H20 (9 if BMI≥25) until start of emergence preoxygenation. Unless the patient´s SpO2 falls below 90%, the FiO2 remains unchanged throughout the procedure. First CT scan after completion of surgery, before emergence. After the first CT scan and immediately before start of emergence preoxygenation, this group will have the PEEP exchanged for zero PEEP (ZEEP). ZEEP will remain until the study subjects are extubated. Second CT scan approx. 30 min after extubation.	Procedure: ZEEP; Zero positive end-expiratory pressure (ZEEP) during emergence preoxygenation and awakening.; Other Names: Device: Ventilatory setting ZEEP
Active Comparator: PEEP at awakening; Controlled ventilation with tidal volume of 7 mL/kg of ideal body weight and respiratory frequency 10. 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 (PEEP) is set to 7 or 9 cm H20 (9 if BMI≥25) even after start of emergence preoxygenation. Unless the patient´s SpO2 falls below 90%, the FiO2 remains unchanged throughout the procedure. First CT scan after completion of surgery, before emergence. After the first CT scan, this group will have PEEP remained until the study subjects are extubated. Second CT scan approx. 30 min after extubation.	Procedure: PEEP; Positive end-expiratory pressure remains during emergence preoxygenation and awakening and until the study subject is extubated.; Other Names: Device: Ventilatory setting PEEP

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in atelectasis area	Atelectasis area as studied by computed tomography.	Within 3 hours from induction of anesthesia. First CT after surgery, before emergence. Second CT approx 25 min after extubation. Study complete after that, no further CT.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in oxygenation	Arterial blood samples will be collected for measurement of arterial oxygen partial pressure.	Within 3 hours from induction of anesthesia. First blood gas after surgery, before emergence. Second approx 25 min after extubation. Study complete after that, no further blood gases.

Collaborators and Investigators

• Sponsor: Region Västmanland
• Investigators: Study Director: Lennart Edmark, M.D., Ph.D., Region Västmanland

Study record dates

Study Major Dates

• Study Start (Actual): December 4, 2017
• Primary Completion (Actual): August 28, 2018
• Study Completion (Actual): August 28, 2018

Study Registration Dates

• First Submitted: November 8, 2017
• First Submitted That Met QC Criteria: November 19, 2017
• First Posted (Actual): November 24, 2017

Study Record Updates

• Last Update Posted (Actual): September 5, 2018
• Last Update Submitted That Met QC Criteria: September 4, 2018
• Last Verified: September 1, 2018

More Information

Terms related to this study

• Keywords: Computed tomography; Mechanical ventilation; Atelectasis; Oxygenation; Positive end-expiratory pressure; General anesthesia
• Additional Relevant MeSH Terms: Respiratory Tract Diseases; Lung Diseases; Pulmonary Atelectasis
• Other Study ID Numbers: Dnr 2017/267

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: Yes
• IPD Plan Description: Please email request to the study principal investigator.
• IPD Sharing Time Frame: Data will be available within 6 months of study completion.
• IPD Sharing Access Criteria: Data access requests will be reviewed by a review panel at the Center for Clinical Research, Västerås. Requestors will be required to sign a data acess agreement.
• IPD Sharing Supporting Information Type: Study Protocol; Statistical Analysis Plan (SAP)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No