Optimal PEEP for Postoperative Oxygenation and Lung Aeration (ULTRASVENT-2) (ULTRASVENT-2)

May 23, 2026 updated by: Moscow Multidisciplinary Clinical Center "Kommunarka"

Effect of Positive End-Expiratory Pressure (PEEP) Level on Postoperative Oxygenation and Lung Aeration Assessed by Lung Ultrasound Monitoring: A Multicenter Randomized Controlled Trial (ULTRASVENT-2)

The purpose of this multicenter, randomized controlled trial (ULTRASVENT-2) is to evaluate the effect of different positive end-expiratory pressure (PEEP) levels on postoperative oxygenation and lung aeration in adult patients undergoing elective non-cardiac and non-thoracic surgery under general anesthesia. Moving away from traditional binary outcomes, this study utilizes a continuous functional metric, the non-invasive oxygenation index SpO2/FiO2 (S/F ratio), as the primary endpoint to precisely capture the degree of respiratory function preservation.

Patients will be stratified into four distinct surgical cohorts based on the type and aggressiveness of the procedure: non-abdominal surgery, major open abdominal surgery, major laparoscopic abdominal surgery, and low-trauma laparoscopic surgery. This adaptive design aims to investigate how protective PEEP strategies interact with varying degrees of surgical trauma and intraoperative pneumoperitoneum, allowing the optimization of mechanical ventilation parameters for routine clinical practice.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Postoperative pulmonary complications remain a significant cause of morbidity and prolonged hospital stay after major surgical interventions under general anesthesia. While positive end-expiratory pressure (PEEP) is widely used to prevent alveolar collapse, the optimal target levels across different surgical sub-types remain controversial in modern anesthesiology. This trial aims to establish robust clinical evidence regarding perioperative lung protection using a comprehensive functional-anatomical approach.

Primary Endpoint and Measurement Standardization:

The primary outcome of the trial is the non-invasive oxygenation index, the S/F ratio (SpO2/Fraction of inspired oxygen), assessed exactly 2 hours post-extubation in the Post-Anesthesia Care Unit (PACU) and tracked dynamically over the first 24 hours of the postoperative period. To eliminate confounding variables and ensure absolute reproducibility across participating centers, the primary endpoint measurement is strictly standardized according to the following criteria:

  1. Room Air Breathing (FiO2 0.21): The evaluation is performed while the patient breathes atmospheric air without supplemental oxygen. This eliminates the masking of intrapulmonary shunts and prevents hyperoxia-induced absorption atelectasis.
  2. Patient Position: The patient must be placed in a strict supine position. This positioning represents the most physiologically challenging state for the respiratory system, inducing cranial displacement of the diaphragm and maximizing gravity-dependent alveolar collapse.
  3. Full Wakefulness Criteria: The measurement is executed only when the patient reaches a full awake status, defined as a modified Post Anesthesia Recovery Score (PARS) greater than 8, with the specific ventilation sub-score being equal to 2 (ability to deep breathe and cough freely). This cognitive and motor filter guarantees that any recorded functional impairment is caused by true parenchymal collapse rather than residual neuromuscular blockade or opioid-induced respiratory depression.

Differentiated Lung Ultrasound (LUS) Track:

To identify the anatomical substrate behind changes in gas exchange, regional lung aeration patterns will be recorded as the key secondary endpoint using a delta LUS score (postoperative score minus preoperative baseline). The diagnostic burden on the investigators is optimized using two parallel diagnostic tracks:

  • Express Track (Strata 1 and 4): A rapid, 2-zone simplified protocol focusing exclusively on the most gravity-dependent bilateral dorsal-basal sectors (Zone 6). This assessment takes 2 to 3 minutes and minimizes interference with routine PACU workflows.
  • Panoramic Mapping Track (Strata 2 and 3): A comprehensive 12-zone thoracic mapping performed under Intensive Care Unit (ICU) conditions. Furthermore, a nested validation sub-study will incorporate high-resolution chest computed tomography (CT) scans performed strictly based on clinical indications (such as refractory hypoxemia or suspected pneumonia). CT data will serve as the gold standard reference to calculate the true sensitivity and specificity of the 12-zone ultrasound findings.

Surgical Stratification and Sample Size Design:

Patients will be randomized in a 1:1 ratio to receive either a fixed standard (lower) PEEP or a fixed higher PEEP strategy throughout the intraoperative period (from intubation to extubation). Randomization is performed independently within 4 parallel strata to achieve a total sample size of 320 to 360 patients:

  • Strata 1: Non-abdominal surgery (n = 100; PEEP 5 cm H2O versus PEEP 8 cm H2O).
  • Strata 2: Major open abdominal surgery (n = 60 to 80; PEEP 5 cm H2O versus PEEP 8 cm H2O).
  • Strata 3: Major laparoscopic abdominal surgery (n = 60 to 80; PEEP 7 cm H2O versus PEEP 12 cm H2O).
  • Strata 4: Low-trauma laparoscopic surgery (n = 100; PEEP 5 cm H2O versus PEEP 12 cm H2O).

Statistical Analysis Framework:

Data processing will be conducted in the jamovi software environment using General Linear Models (GLM). The analysis will incorporate continuous and categorical baseline covariates (Body Mass Index, age, ASA physical status, and duration of surgery) to reduce residual variance. A key element of the statistical plan is the evaluation of interaction effects between the PEEP level and the specific surgical stratum to determine whether a higher PEEP provides a universal benefit or if its protective role is strictly dependent on the surgical phenotype.

Implementation Protocol Phases:

To guarantee data integrity and eliminate investigator bias, the project is structured into four consecutive logical phases:

Phase 1: Regulatory start, including central registration on ClinicalTrials.gov, Local Ethics Committee (LEC) submission and approval, and prospective publication of the formal Study Protocol manuscript.

Phase 2: Standardized hands-on calibration and training of the core investigator team (4 to 6 specialists) regarding precise zone identification and digital data entry.

Phase 3: A mandatory run-in period dedicated to inter-rater reliability testing. Each investigator must scan a test cohort, and the enrollment of randomized trial patients can begin only after achieving an inter-operator consensus threshold defined as a Cohen's Kappa coefficient greater than or equal to 0.7 and an absolute category agreement greater than or equal to 80%.

Phase 4: Active enrollment utilizing an adaptive recruitment strategy. The trial will commence by enrolling patients in high-volume, low-risk groups (Strata 1 and 4) to seamlessly refine logistical and database processes before activating the complex and labor-intensive ICU-based cohorts (Strata 2 and 3).

Study Type

Interventional

Enrollment (Estimated)

360

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Ivan Shcheparev, MD, PhD
  • Phone Number: +7 901 908 90 88
  • Email: is22@list.ru

Study Locations

  • Russia
    • Moscow
      • Moscow, Moscow, Russia, 108814
        • Moscow Multi-disciplinary Clinical Center "Kommunarka"
        • Contact:
          • Ivan Shcheparev, MD, PhD
          • Phone Number: +7 901 908 90 88
          • Email: is22@list.ru

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age greater than or equal to 18 years.
  • Planned elective non-cardiac and non-thoracic surgical intervention requiring general anesthesia with mechanical ventilation.
  • Airway protection utilizing an endotracheal tube.
  • Assignment to one of the four specific surgical strata: non-abdominal, major open abdominal, major laparoscopic abdominal, or low-trauma laparoscopic surgery.
  • Baseline lung ultrasound showing no pathological findings, corresponding to a total preoperative LUS score of 0.
  • Technical feasibility of performing a postoperative lung ultrasound within the first 2 hours after the completion of surgery.
  • Signed written informed consent to participate in the clinical trial.

Exclusion Criteria:

  • Planned cardiac or thoracic surgery (e.g., coronary artery bypass grafting, valve replacement, heart transplantation, lung resection, esophageal surgery).
  • Pneumothorax diagnosed before or during the surgical procedure.
  • Inability to adequately visualize the target dorsal-basal lung zones by ultrasound due to physical limitations (e.g., morbid obesity, massive surgical dressings, anatomical anomalies, or dermatological lesions in the scanning area).
  • Presence of hydrothorax detected on the baseline preoperative ultrasound.
  • Confirmed perioperative aspiration of gastric contents or other foreign material.
  • Any pathological changes identified during the baseline ultrasound of the dorsal-basal lung regions (a total preoperative LUS score greater than 0).
  • Requirement for massive blood transfusion during the surgery, defined according to local institutional criteria.
  • Surgical interventions directly involving or violating the diaphragm.
  • Expected inability to conduct reliable postoperative clinical and ultrasound assessments (e.g., need for deep sedation preventing wakefulness and contact, or planned transfer to another facility).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Standard PEEP Strategy
Patients randomized to this arm will receive a fixed, standard (lower) level of Positive End-Expiratory Pressure (PEEP) throughout the intraoperative period (from intubation to extubation). The specific PEEP value is determined strictly by the surgical stratum: 5 cm H2O for Strata 1 (Non-abdominal surgery), 5 cm H2O for Strata 2 (Major open abdominal surgery), 5 cm H2O for Strata 3 (Major laparoscopic abdominal surgery), and 5 cm H2O for Strata 4 (Low-trauma laparoscopic surgery). All other mechanical ventilation parameters remain standardized (tidal volume 6-8 mL/kg of ideal body weight).
Procedure: Intraoperative Positive End-Expiratory Pressure (PEEP) Regulation
Application of fixed PEEP levels calculated according to surgical aggressiveness and the presence of pneumoperitoneum. Standard PEEP arm utilizes PEEP values of 5 cm H2O. Higher PEEP arm utilizes protective PEEP values of 8 or 12 cm H2O. The assigned PEEP strategy is initiated immediately following endotracheal intubation and maintained continuously until extubation.
Experimental: Higher PEEP Strategy
Patients randomized to this arm will receive a fixed, higher level of Positive End-Expiratory Pressure (PEEP) designed for protective lung ventilation throughout the intraoperative period. The specific PEEP value is tailored to the surgical stratum and abdominal risk: 8 cm H2O for Strata 1 (Non-abdominal surgery), 8 cm H2O for Strata 2 (Major open abdominal surgery), 12 cm H2O for Strata 3 (Major laparoscopic abdominal surgery), and 12 cm H2O for Strata 4 (Low-trauma laparoscopic surgery). All other mechanical ventilation parameters remain standardized (tidal volume 6-8 mL/kg of ideal body weight).
Procedure: Intraoperative Positive End-Expiratory Pressure (PEEP) Regulation
Application of fixed PEEP levels calculated according to surgical aggressiveness and the presence of pneumoperitoneum. Standard PEEP arm utilizes PEEP values of 5 cm H2O. Higher PEEP arm utilizes protective PEEP values of 8 or 12 cm H2O. The assigned PEEP strategy is initiated immediately following endotracheal intubation and maintained continuously until extubation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Non-invasive oxygenation index (SpO2/FiO2 ratio)
Time Frame: Assessed at 3 time points: preoperatively (baseline); exactly 2 hours post-extubation; and 24 hours post-operation.

The primary functional outcome is the SpO2/FiO2 (S/F) ratio, a continuous metric indicating the degree of lung oxygenation. The S/F ratio is calculated by dividing the peripheral capillary oxygen saturation (SpO2) by the fraction of inspired oxygen (FiO2). To ensure standardization, postoperative measurements are performed on room air in a supine position. Measurements are recorded strictly when the patient achieves full wakefulness, which is verified using the modified Post Anesthesia Recovery Score (PARS) as a readiness criteria. The PARS scale ranges from a minimum of 0 to a maximum of 10, where higher scores indicate a better clinical recovery.

Note: The reported outcome is solely the S/F ratio value; the PARS score is used exclusively as a clinical condition to initiate the S/F measurement and is not aggregated into the final outcome value.
Assessed at 3 time points: preoperatively (baseline); exactly 2 hours post-extubation; and 24 hours post-operation.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of Postoperative Pulmonary Complications (PPCs)
Time Frame: From the end of surgery up to 7 days post-operation.
The composite clinical outcome evaluates the total percentage of patients developing at least one severe respiratory adverse event in the postoperative period. PPCs are strictly defined as the presence of one or more of the following: confirmed hospital-acquired pneumonia, prolonged requirement for supplemental oxygen therapy lasting longer than 24 hours, or the onset of refractory hypoxemia necessitating unexpected transfer to the Intensive Care Unit for non-invasive or invasive mechanical ventilation.
From the end of surgery up to 7 days post-operation.
Postoperative lung ultrasound score and aeration patterns
Time Frame: Exactly 2 hours post-extubation in the Post-Anesthesia Care Unit (PACU) or Intensive Care Unit (ICU).

Evaluation of the absolute postoperative Lung Ultrasound (LUS) score to assess anesthesia-induced alveolar collapse. A differentiated protocol is used based on surgical strata.

Strata 1 and 4 use a 2-zone express protocol targeting dorsal-basal sectors (total scale range: minimum 0 to maximum 6).

Strata 2 and 3 use a comprehensive 12-zone panoramic thoracic mapping protocol (total scale range: minimum 0 to maximum 36).

For both LUS scales, higher scores indicate a worse outcome (more severe loss of lung aeration and atelectasis). Specific qualitative acoustic patterns (e.g., multiple B-lines, subpleural consolidations, or static bronchograms) are also recorded to validate the numerical LUS score.
Exactly 2 hours post-extubation in the Post-Anesthesia Care Unit (PACU) or Intensive Care Unit (ICU).
Incidence of Intraoperative Hemodynamic Instability
Time Frame: Intraoperatively (from the moment of endotracheal intubation until extubation).
Frequency of intraoperative hemodynamic instability episodes directly related to mechanical ventilation settings, specifically measured as the requirement for the initiation or dose increase of vasopressor support (ephedrine, phenylephrine, or norepinephrine) to maintain a mean arterial pressure (MAP) greater than 65 mm Hg.
Intraoperatively (from the moment of endotracheal intubation until extubation).

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Moscow Multidisciplinary Clinical Center "Kommunarka"

Investigators

  • Principal Investigator: Ivan Shcheparev, MD, PhD, Moscow Multi-disciplinary Clinical Center "Kommunarka"
  • Study Director: Denis Protsenko, MD, PhD, Professor, Moscow Multi-disciplinary Clinical Center "Kommunarka"
  • Study Chair: Efim Shifman, MD, PhD, Professor, Moscow Multi-disciplinary Clinical Center "Kommunarka"

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

July 1, 2026

Primary Completion (Estimated)

December 1, 2026

Study Completion (Estimated)

December 20, 2026

Study Registration Dates

First Submitted

May 19, 2026

First Submitted That Met QC Criteria

May 23, 2026

First Posted (Actual)

May 29, 2026

Study Record Updates

Last Update Posted (Actual)

May 29, 2026

Last Update Submitted That Met QC Criteria

May 23, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ULTRASVENT-2

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data (IPD) that underlie the results reported in the primary publication (including baseline characteristics, intraoperative mechanical ventilation parameters, lung ultrasound scores, and clinical postoperative outcomes) will be made publicly available to ensure absolute transparency and academic reproducibility.

IPD Sharing Time Frame

Data will become available immediately following the official publication of the primary trial results, with no specified end date.

IPD Sharing Access Criteria

The dataset will be openly accessible to any researcher, clinician, or analyst interested in replicating the study findings, conducting systematic reviews, or performing secondary meta-analyses. The data will be hosted publicly, and no formal research proposal review or data use agreements are required for access.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • ICF
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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