Flow-Controlled vs Volume-Controlled Ventilation in Morbidly Obese Patients Undergoing Laparoscopic Bariatric Surgery

Investigation of the Effects of Flow-Controlled Ventilation and Volume-Controlled Ventilation on Pulmonary Dynamics and Hemodynamics in Morbidly Obese Patients Undergoing Laparoscopic Bariatric Surgery

The goal of this clinical trial is to compare the effects of flow-controlled ventilation (FCV) and volume-controlled ventilation (VCV) on hemodynamic and respiratory parameters in obese patients undergoing elective laparoscopic bariatric surgery. The main questions it aims to answer are:

Does FCV provide better intraoperative hemodynamic and respiratory stability compared to VCV during laparoscopic bariatric surgery? Is FCV a safe and feasible ventilation strategy under high intraabdominal pressure and position changes required in bariatric surgery?

Researchers will compare FCV group to VCV group to see if FCV improves intraoperative respiratory mechanics and hemodynamic parameters.

Participants will:

Undergo elective laparoscopic bariatric surgery with BMI >40 kg/m² (ASA I-III) Receive either flow-controlled or volume-controlled ventilation with individualized PEEP and tidal volume of 6-8 ml/kg predicted body weight Have intraoperative hemodynamic and respiratory parameters monitored at regular intervals, including arterial blood gas analysis Be followed postoperatively for oxygen therapy requirement and intensive care need

Study Overview

• Status: Recruiting
• Conditions: Obesity, Morbid; Mechanical Ventilation; Bariatric Surgery (Sleeve Gastrectomy )
• Intervention / Treatment: Device: Flow-Controlled Ventilation (FCV); Device: Volume-Controlled Ventilation (VCV)

Detailed Description

Laparoscopic surgery is associated with significant physiological changes due to pneumoperitoneum, which adversely affects hemodynamic and respiratory parameters, thereby complicating intraoperative anesthetic management. These challenges are particularly pronounced in obese patients, who present with reduced functional residual capacity and other physiological alterations that impact both intraoperative and postoperative outcomes.

Although bariatric surgery has conventionally been managed with volume-controlled ventilation (VCV), recent studies have highlighted the potential benefits of flow-controlled ventilation (FCV) in terms of safety and contribution to lung-protective ventilation strategies.

This study primarily aims to compare the effects of FCV and VCV on intraoperative hemodynamic and respiratory function dynamics in patients undergoing bariatric surgery. Secondarily, the study evaluates the clinical feasibility and safety of FCV under the high intraabdominal pressures and position changes required during bariatric procedures.

Study Design:

This study includes 34 patients with BMI >40 kg/m² classified as ASA I-III scheduled for elective laparoscopic bariatric surgery. Seventeen patients were prospectively managed with FCV, while data from 17 patients managed with VCV were retrospectively reviewed. All patients received standard monitoring plus intra-arterial blood pressure monitoring. Anesthesia induction and maintenance protocols were identical across both groups.

Ventilation Protocol:

In the FCV group, a tidal volume (VT) of 6-8 ml/kg predicted body weight was targeted, and positive end-expiratory pressure (PEEP) was individualized based on compliance following CO₂ insufflation. The same tidal volume strategy was applied in the VCV group with PEEP titration performed in eligible patients.

Measurements:

The following parameters were recorded after intubation, after insufflation, and at 30-minute intervals intraoperatively: mean arterial pressure (MAP), heart rate, peripheral oxygen saturation (SpO₂), plateau airway pressure (Pplat), peak airway pressure (Ppeak), driving pressure, end-tidal CO₂ (EtCO₂), minute volume, respiratory rate (RR), airway resistance (Raw), and static compliance (Cstatic) calculated as VT/(Pplat-PEEP). Arterial blood gas parameters including pH, PaCO₂, PaO₂, SaO₂, hemoglobin, and lactate were also recorded. Postoperative oxygen therapy requirement and intensive care unit admission were monitored.

• Study Type: Observational
• Enrollment (Estimated): 34

Contacts and Locations

• Study Contact: Name: Tugce Ozdogan, MD; Phone Number: +90 5353588818; Email: tugceeskin@yahoo.com.tr

Study Locations

• Turkey (Türkiye)
  • Ankara, Turkey (Türkiye), 06230
    • Recruiting
    • Ankara Education and Research Hospital
    • Contact: Tugce Ozdogan, MD; Phone Number: +90 5353588818; Email: tugceeskin@yahoo.com.tr
    • Sub-Investigator: Asutay Goktug, MD,PhD
    • Sub-Investigator: Hülya Basar, MD,Phd
    • Sub-Investigator: Mustafa Kaan Bozkurt, MD
    • Sub-Investigator: Cetin Kaymak, MD, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adult morbidly obese patients (BMI ≥40 kg/m²) aged 18-65 years, classified as ASA I-III, scheduled for elective laparoscopic bariatric surgery at Ankara Training and Research Hospital.

Description

Inclusion Criteria:

• Age between 18 and 65 years American Society of Anesthesiologists (ASA) physical status I, II, or III Body Mass Index (BMI) ≥ 40 kg/m² Scheduled for elective laparoscopic bariatric surgery Willing to participate in the study

Exclusion Criteria:

• ASA physical status IV or V Emergency surgical procedures Pregnant patients Patients requiring vasopressor support to maintain mean arterial pressure above 65 mmHg intraoperatively Patients with advanced pulmonary disease Patients who decline to participate in the study

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
FCV Group; Patients undergoing elective laparoscopic bariatric surgery managed with flow-controlled ventilation (FCV) with tidal volume of 6-8 ml/kg predicted body weight and individualized PEEP based on compliance following CO₂ insufflation.	Device: Flow-Controlled Ventilation (FCV); Patients were ventilated using flow-controlled ventilation with a tidal volume of 6-8 ml/kg predicted body weight. PEEP was individualized based on respiratory compliance following CO₂ insufflation.; Other Names: FCV
VCV Group; Patients undergoing elective laparoscopic bariatric surgery managed with volume-controlled ventilation (VCV) with tidal volume of 6-8 ml/kg predicted body weight and PEEP titration performed in eligible patients. Data collected retrospectively.	Device: Volume-Controlled Ventilation (VCV); Patients were ventilated using volume-controlled ventilation with a tidal volume of 6-8 ml/kg predicted body weight. PEEP titration was performed in eligible patients.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intraoperative Respiratory Mechanics	Comparison of driving pressure between FCV and VCV groups at defined intraoperative time points.	From intubation to end of surgery, measured after intubation, after insufflation, and at 30-minute intervals intraoperatively
Mean Arterial Pressure	Comparison of mean arterial pressure (MAP) between FCV and VCV groups at defined intraoperative time points.	From preoperative baseline to end of surgery, measured before surgery, after intubation, after insufflation, at 30-minute intervals intraoperatively, and at end of surgery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pa02/Fi02 ratio	Comparison of Horowitz index between FCV and VCV groups.	From intubation to end of surgery, measured after intubation, after insufflation, at 30-minute intervals intraoperatively and at the end of the surgery.
Postoperative Oxygen Theraphy Need	Comparison of percentage of participants requiring postoperative oxygen therapy requirement between FCV and VCV groups.	Within 24 hours after surgery
Postoperative Intensive Unit Admission	Comparison of the number of patients requiring admission to the intensive care unit between the FCV and VCV groups.	Within 24 hours after surgery
Arterial Partial Pressure of Carbon Dioxide (PaCO2)	Comparison of arterial partial pressure of carbon dioxide (PaCO2) between the FCV and VCV groups to evaluate efficiency of carbon dioxide elimination at defined time points.	From intubation to the end of surgery, measured after intubation, after insufflation, and at 30-minute intervals intraoperatively and at the end of the operation

Collaborators and Investigators

• Sponsor: Ankara Training and Research Hospital

Study record dates

Study Major Dates

• Study Start (Actual): March 15, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): August 1, 2026

Study Registration Dates

• First Submitted: June 1, 2026
• First Submitted That Met QC Criteria: June 7, 2026
• First Posted (Actual): June 11, 2026

Study Record Updates

• Last Update Posted (Actual): June 11, 2026
• Last Update Submitted That Met QC Criteria: June 7, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Bariatric surgery; Respiratory mechanics; Volume-controlled ventilation; Lung-protective ventilation; Flow-controlled ventilation
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Obesity; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity, Morbid
• Other Study ID Numbers: E-25-418

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual participant data will be shared upon reasonable request.
• IPD Sharing Time Frame: Beginning 6 months after publication and ending 5 years following article publication
• IPD Sharing Access Criteria: Individual participant data will be available upon reasonable request to the corresponding author.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No