Impact of High Versus Lower Oxygen Fraction Prior to Extubation on Postoperative Pulmonary Atelectasis Measured With EIT

NCT06538740 | Completed

• 1 other identifier: IRB: 2023P000223
• Study Type: interventional
• Target: 48
• Locations: 1 country
• Sites: 1

Brief Summary

Patients undergoing general anesthesia require mechanical ventilation (artificial delivery of air and oxygen to their lungs). It is well known that during mechanical ventilation, so-called atelectasis formation occurs. This is a condition characterized by partial or complete collapse of lung tissue that can result in a reduction in oxygen uptake through the lung. A known risk factor for atelectasis formation during mechanical ventilation is the utilization of high oxygen concentration, as the oxygen molecules are absorbed in the lung, which then can lead to collapse of the tissue. Despite the proven association, standard operating procedure at the end of anesthesia still requires utilization of 100% oxygen. Its justification is the goal to ensure sufficient oxygenation throughout the extubation phase. However, clinical observation doesn't show a lack of oxygenation in this phase, but the patient is still exposed to the risk of atelectasis formation. This study aims to investigate the hypothesis of whether the utilization of reduced inspiratory oxygen concentration before extubation (70% or 40% compared to 100%) reduces atelectasis formation. The study was originally planned to randomize 24 patients to either 70% or 100% inspiratory oxygen concentration at the end of anaesthesia. After completion of this first phase, the study was amended to enroll another 24 patients randomized to 40% or 100% inspiratory oxygen concentration at the end of anaesthesia. Of note, both concentrations are still higher than when breathing room air in, which has of 21% oxygen. During the intervention, parameters such as the oxygen content in the blood (oxygen saturation, SpO₂), heart rate, and blood pressure are recorded, and atelectasis formation is measured using a technique called electrical impedance tomography (EIT). EIT measurements are performed at designated time points during the procedure. Anesthesia care providers are asked to document procedural, patient, and ventilator data in a questionnaire. Secondary outcomes are the homogeneity and distribution of air measured with EIT, as well as some clinical outcomes including post-extubation desaturation (\<90% SpO₂), incidence of re-intubation or non-invasive ventilation, and the Post-anesthesia Care Unit (PACU) length of stay.

Conditions

Atelectasis

Keywords

Pulmonary Atelectasis [C08.381.730]; Oxygen [D01.268.185.550, D01.362.670]; Electrical impedance tomography; Center of Ventilation; lung aeration; anesthesia

Outcome Measures

Primary Outcomes (1)

• The shift of Center of Ventilation (CoV), measured through Electrical Impedance Tomography (EIT) in %.

  The Center of Ventilation (CoV) is a variable based on the EIT. It is calculated after the initial measurements and defines the most ventilated area of the lung. Assumptions on atelectasis formation can be drawn when the CoV shifts to more ventral areas than measured before. Primary outcome is the absolute difference between the first measurement (before induction) and the measurement directly after extubation in %.

  The CoV is measured at six points: pre-induction, post-intubation, pre-washout, pre-extubation, 1 min post-extubation, and 60 min post-extubation in the PACU. The primary outcome is the difference between pre-induction and 1 min post-extubation.

Secondary Outcomes (6)

• The 1st secondary outcome is the variation of the inhomogeneity index within each patient, measured through Electrical Impedance Tomography (EIT).

  The inhomogeneity index is measured at six points: pre-induction, post-intubation, pre-washout, pre-extubation, 1 min post-extubation, and 60 min post-extubation in the PACU.

• The 2nd secondary outcome is the distribution of lung aeration, measured through Electrical Impedance Tomography (EIT).

  The distribution of lung aeration is measured at six points: pre-induction, post-intubation, pre-washout, pre-extubation, 1 min post-extubation, and 60 min post-extubation in the PACU.

• Minutes of hypoxemia in the first 60 minutes after extubation

  The SpO2 data analysis starts with the time the patient enters the PACU and is continued until the patient is discharged from the PACU, which is typically one to two hours after the end of surgery.

• Re-intubation or the need for unplanned non-invasive ventilation within 7 days.

  7 days post-operative

• Unplanned admission to either ICU, IMC or a normal unit.

  Unplanned admission to either ICU, ICM or a normal unit after the PACU stay is determined in the time frame after end of surgery and up to 7 days after the surgery.

Study Arms (2)

Control group

NO INTERVENTION

Ventilating the patient with 100% oxygen concentration during the wash out phase, before extubation

Intervention group

ACTIVE COMPARATOR

Ventilating the patient with lower (40 or 70%) oxygen concentration during the wash out phase, before extubation

Procedure: Ventilating the patient with lower (40 or 70%) oxygen concentration during the wash out phase, before extubation

Interventions

Ventilating the patient with lower (40 or 70%) oxygen concentration during the wash out phase, before extubation PROCEDURE

The investigated intervention is the application of 70% inspired oxygen compared to 100% inspired oxygen during the anesthetic washout, right before extubation of the patient for the first 24 enrolled patients, and 40% inspired oxygen compared to 100% inspired oxygen for the subsequently enrolled 24 patients. Before and after the intervention EIT measurements are performed at designated time points to assess lung aeration and calculate the center of ventilation. This information allows assumptions on atelectasis formation in the patients' lung.

Intervention group

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age ≥ 18 years
• Elective surgery with general anesthesia and endotracheal intubation
• Expected duration of surgery 1-5 hours
• Consent obtained from patient

You may not qualify if:

• Patients with inability to give written informed consent
• American Society of Anesthesiologists (ASA) physical status\> IV
• Morbid obesity BMI \> 40
• Suspected pregnancy and lactation
• Cardiac or thoracic surgery
• Patients with thoracic epidural catheters
• Patients with active implantable devices, such as pacemakers, cardioverter defibrillators, or neurostimulators
• Compromised airways
• Impaired oxygenation at baseline or during surgery

Sponsors & Collaborators

• Beth Israel Deaconess Medical Center: lead

Study Sites (1)

Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School

Boston, Massachusetts, 02215, United States

Location

Related Publications (7)

• Frerichs I, Amato MB, van Kaam AH, Tingay DG, Zhao Z, Grychtol B, Bodenstein M, Gagnon H, Bohm SH, Teschner E, Stenqvist O, Mauri T, Torsani V, Camporota L, Schibler A, Wolf GK, Gommers D, Leonhardt S, Adler A; TREND study group. Chest electrical impedance tomography examination, data analysis, terminology, clinical use and recommendations: consensus statement of the TRanslational EIT developmeNt stuDy group. Thorax. 2017 Jan;72(1):83-93. doi: 10.1136/thoraxjnl-2016-208357. Epub 2016 Sep 5.

  PMID: 27596161 BACKGROUND

• Riva T, Pascolo F, Huber M, Theiler L, Greif R, Disma N, Fuchs A, Berger-Estilita J, Riedel T. Evaluation of atelectasis using electrical impedance tomography during procedural deep sedation for MRI in small children: A prospective observational trial. J Clin Anesth. 2022 May;77:110626. doi: 10.1016/j.jclinane.2021.110626. Epub 2021 Dec 10.

  PMID: 34902800 BACKGROUND

• Schaefer MS, Wania V, Bastin B, Schmalz U, Kienbaum P, Beiderlinden M, Treschan TA. Electrical impedance tomography during major open upper abdominal surgery: a pilot-study. BMC Anesthesiol. 2014 Jul 5;14:51. doi: 10.1186/1471-2253-14-51. eCollection 2014.

  PMID: 25018668 BACKGROUND

• Victorino JA, Borges JB, Okamoto VN, Matos GF, Tucci MR, Caramez MP, Tanaka H, Sipmann FS, Santos DC, Barbas CS, Carvalho CR, Amato MB. Imbalances in regional lung ventilation: a validation study on electrical impedance tomography. Am J Respir Crit Care Med. 2004 Apr 1;169(7):791-800. doi: 10.1164/rccm.200301-133OC. Epub 2003 Dec 23.

  PMID: 14693669 BACKGROUND

• Benoit Z, Wicky S, Fischer JF, Frascarolo P, Chapuis C, Spahn DR, Magnusson L. The effect of increased FIO(2) before tracheal extubation on postoperative atelectasis. Anesth Analg. 2002 Dec;95(6):1777-81, table of contents. doi: 10.1097/00000539-200212000-00058.

  PMID: 12456458 BACKGROUND

• Rothen HU, Sporre B, Engberg G, Wegenius G, Reber A, Hedenstierna G. Prevention of atelectasis during general anaesthesia. Lancet. 1995 Jun 3;345(8962):1387-91. doi: 10.1016/s0140-6736(95)92595-3.

  PMID: 7760608 BACKGROUND

• Reber A, Engberg G, Wegenius G, Hedenstierna G. Lung aeration. The effect of pre-oxygenation and hyperoxygenation during total intravenous anaesthesia. Anaesthesia. 1996 Aug;51(8):733-7. doi: 10.1111/j.1365-2044.1996.tb07885.x.

  PMID: 8795314 BACKGROUND

MeSH Terms

Conditions

Pulmonary Atelectasis

Condition Hierarchy (Ancestors)

Lung Diseases; Respiratory Tract Diseases

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Director of the Center for Anesthesia Research Excellence (CARE) Division Director of Thoracic Anesthesia

Model Details: This study is a single blinded, randomized, trial comparing two study groups ("intervention" and "control")

Study Record Dates

• First Submitted: July 2, 2024
• First Posted: August 6, 2024
• Study Start: September 27, 2024
• Primary Completion: May 15, 2025
• Study Completion: May 22, 2025
• Last Updated: September 25, 2025

Record last verified: 2025-09

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)