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NCT Number: NCT07430111

Flow-Controlled Versus Volume-Controlled Ventilation in Bariatric Surgery

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.

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Key information

Conditions

Obesity Bariatric Surgery Body Weight Mechanical Ventilation Nutrition Disorders Nutritional and Metabolic Diseases Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

FCV Group

Procedure

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.

VCV Group

Procedure

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.

Primary outcomes

  1. 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.

Secondary outcomes

  1. 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.

  2. 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.

  3. 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.

Sponsors and collaborators

Lead sponsor

Ankara Etlik City Hospital

Other Gov

Registry information

Official study title

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

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Feb 24, 2026
Registry last updated
Feb 25, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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