Flow-Controlled Versus Volume-Controlled Ventilation in Bariatric Surgery

February 24, 2026 updated by: Atakan Sezgi, Ankara Etlik City Hospital

Comparison of Flow-Controlled and Volume-Controlled Ventilation During Bariatric Surgery: A Prospective Randomized Trial

This prospective trial aims to compare the effects of flow-controlled ventilation (FCV) and volume-controlled ventilation (VCV) on intraoperative airway pressures and oxygenation in bariatric surgery under general anesthesia. Obesity is associated with altered respiratory mechanics, reduced functional residual capacity, and increased airway pressures, making the selection of an optimal ventilation strategy particularly important in this patient population.

Adult patients aged 18-65 years with a body mass index ≥30 kg/m² and American Society of Anesthesiologists (ASA) physical status II-III will be allocated to receive either FCV or VCV as part of routine intraoperative mechanical ventilation. Ventilatory parameters, including peak and plateau airway pressures, pulmonary compliance, will be recorded at predefined intraoperative time points.

The primary endpoint of the study is the PaO₂ value measured at the 20th minute under an FiO₂ of 0.8-1.0.

By providing comparative data on respiratory mechanics and oxygenation, this study aims to contribute to the identification of lung-protective ventilation strategies and to optimize intraoperative ventilatory management in bariatric surgery.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

40

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 Locations

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 between 18 and 65 years
  • Body mass index (BMI) ≥ 30 kg/m²
  • ASA physical status II-III

Exclusion Criteria:

  • ASA physical status I or IV and above
  • Known or previously diagnosed pulmonary disease
  • Patients with severe preoperative pulmonary function impairment (e.g., FEV₁ < 50% predicted, severe restrictive or obstructive pathology)
  • Patients with markedly altered lung anatomy or function due to prior major thoracic surgery
  • Patients who were dependent on supplemental oxygen therapy in the preoperative period
  • Refusal to participate in the study or inability to comply with study procedures

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: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: FCV Group

Patients allocated to the FCV group will receive intraoperative mechanical ventilation using a flow-controlled ventilation mode during surgery under general anesthesia. %50 FiO₂ will be applied, and a driving pressure of 12 cmH₂O will be used.

Following insufflation, the patient's FiO₂ will be maintained between 0.8 and 1.0 for 20 minutes.

After the 20th minute, ventilator settings will be returned to the baseline values.

Tidal volume will be generated and recorded by the ventilator according to the driving pressure and the patient's lung mechanics.

Minute ventilation will be adjusted based on the target tidal volume. The target tidal volume will be set at 6-8 mL/kg (7 mL/kg) with a respiratory rate of 12 breaths/min.

Positive end-expiratory pressure (PEEP) will be maintained at 5 cmH₂O. The respiratory rate will be further titrated to maintain ETCO₂ between 35 and 40 mmHg.
Procedure: FCV Group
Patients allocated to the FCV group will receive intraoperative mechanical ventilation using a flow-controlled ventilation mode during surgery under general anesthesia. Patients will be started on ventilation after intubation with 50% oxygen, driving pressure 12, PEEP 5, and a 1:1 inspiration/expiratory ratio.
Active Comparator: VCV Group
Patients allocated to the VCV group will receive intraoperative mechanical ventilation using a conventional volume-controlled ventilation mode throughout surgery under general anesthesia. Anesthetic induction, monitoring, and perioperative management will follow the same standardized clinical protocols as those used in the FCV group. Ventilatory parameters, including peak and plateau airway pressures and arterial blood gas measurements, will be collected at identical predefined intraoperative time points. This group serves as the comparator arm for evaluating the effects of volume-controlled ventilation on airway pressures and oxygenation in these patients.
Procedure: VCV Group
Patients allocated to the VCV group will receive intraoperative mechanical ventilation using a conventional volume-controlled ventilation mode throughout surgery under general anesthesia. Patients will be started on ventilation after intubation with 50% oxygen, 7 ml/ideal body weight tidal volume, PEEP 5, 12 breaths per minute frequency, and a 1:2 inspiration/expiration ratio.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The PaO₂ value 20 minutes after insufflation.
Time Frame: At 20 minutes after insufflation in the intraoperative period.

The primary endpoint of the study is the PaO₂ value measured at the 20th minute under an FiO₂ of 0.8-1.0. Following insufflation, the patient's FiO₂ will be maintained between 0.8 and 1.0 for 20 minutes.

The primary endpoint of the study is the PaO₂ value measured at the 20th minute under an FiO₂ of 1.0.

After the 20th minute, ventilator settings will be returned to the baseline values.
At 20 minutes after insufflation in the intraoperative period.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The PaO₂ value during perioperative period
Time Frame: At the beginning of the insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.
The PaO₂ values will be measured and recorded using arterial blood gas analysis.
At the beginning of the insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.
Peak airway pressure (Ppeak) values during perioperative period.
Time Frame: At the beginning of the insufflation, 20 minutes after insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.
Ppeak will be measured and recorded.
At the beginning of the insufflation, 20 minutes after insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.
Plateau airway pressure (Pplateau) values during perioperative period
Time Frame: At the beginning of the insufflation, 20 minutes after insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.
Pplateau will be measured and recorded.
At the beginning of the insufflation, 20 minutes after insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.

Collaborators and Investigators

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

Sponsor

Ankara Etlik City Hospital

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 (Actual)

February 24, 2026

Primary Completion (Estimated)

February 5, 2027

Study Completion (Estimated)

February 18, 2027

Study Registration Dates

First Submitted

February 18, 2026

First Submitted That Met QC Criteria

February 18, 2026

First Posted (Actual)

February 24, 2026

Study Record Updates

Last Update Posted (Actual)

February 25, 2026

Last Update Submitted That Met QC Criteria

February 24, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • AEŞH-EK-2026-011

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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