Flow-Controlled Versus Volume-Controlled Ventilation in Bariatric Surgery

Ankara Etlik City Hospital40 enrolled

Overview

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 Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

SINGLE

Enrollment

Conditions

Obesity Bariatric Surgery

Interventions

FCV GroupPROCEDURE

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 GroupPROCEDURE

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.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 65 Years

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

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.

Time frame: At 20 minutes after insufflation in the intraoperative period.

Secondary Outcomes

The PaO₂ value during perioperative period

The PaO₂ values will be measured and recorded using arterial blood gas analysis.

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

Peak airway pressure (Ppeak) values during perioperative period.

Ppeak will be measured and recorded.

Time frame: 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

Pplateau will be measured and recorded.