Flow-Controlled Versus Volume-Controlled Ventilation in Bariatric Surgery

NCT07430111 | Recruiting

• 1 other identifier: AEŞH-EK-2026-011
• Study Type: interventional
• Target: 40
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Obesity; Bariatric Surgery; Mechanical Ventilation

Keywords

Obesity; Flow-Controlled Ventilation; Volume-Controlled Ventilation

Outcome Measures

Primary Outcomes (1)

• The PaO₂ value 20 minutes after insufflation.

  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 Outcomes (3)

• The PaO₂ value during perioperative period

  At the beginning of the insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.

• Peak airway pressure (Ppeak) values during perioperative period.

  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

  At the beginning of the insufflation, 20 minutes after insufflation, 60 minutes after insufflation, before extubation, 1 hour after extubation.

Study Arms (2)

FCV Group

ACTIVE COMPARATOR

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

VCV Group

ACTIVE COMPARATOR

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

Interventions

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.

FCV Group

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.

VCV Group

Eligibility Criteria

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

You may qualify if:

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

You may not qualify if:

• 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

Sponsors & Collaborators

• Ankara Etlik City Hospital: lead

Study Sites (1)

Ankara Etlik City Hospital

Ankara, 06000, Turkey (Türkiye)

RECRUITING

MeSH Terms

Conditions

Obesity

Condition Hierarchy (Ancestors)

Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER GOV
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: February 18, 2026
• First Posted: February 24, 2026
• Study Start: February 24, 2026
• Primary Completion (Estimated): February 5, 2027
• Study Completion (Estimated): February 18, 2027
• Last Updated: February 25, 2026

Record last verified: 2026-02

Locations

TU (1)