Flow-Controlled vs. Pressure-Controlled Ventilation in CABG: Effects on Lung Aeration and Diaphragm Function (FCV-PCV-DTI-LU)

Comparison of Flow-Controlled Ventilation and Pressure-Controlled Ventilation on Lung Aeration and Diaphragm Function in Patients Undergoing Elective Isolated On-Pump Coronary Artery Bypass Graft Surgery: A Single-Centre Prospective Randomised Controlled Trial

Pulmonary atelectasis and loss of lung aeration are common complications following cardiac surgery with cardiopulmonary bypass (CPB) and are associated with impaired oxygenation and prolonged mechanical ventilation. Diaphragm dysfunction occurring in the perioperative period may further delay extubation and prolong intensive care unit (ICU) stay. Flow-Controlled Ventilation (FCV) is a novel ventilation modality that provides continuous, flow-based delivery of tidal breaths with a triangular flow profile, potentially offering superior dynamic compliance optimisation compared to conventional Pressure-Controlled Ventilation (PCV).

Study Overview

• Status: Not yet recruiting
• Conditions: Coronary Artery Disease; Respiratory Insufficiency; Postoperative Pulmonary Complications; Diaphragm Dysfunction; Pulmonary Atelectasis, Postoperative
• Intervention / Treatment: Procedure: Pressure-Controlled Ventilation (PCV); Procedure: Flow-Controlled Ventilation

Detailed Description

This single-centre, prospective, 1:1 randomised parallel-group controlled trial will compare intraoperative FCV with PCV in adults undergoing elective isolated on-pump coronary artery bypass graft (CABG) surgery. The primary outcome is total lung ultrasound (LUS) score change (0-36 scale) from baseline (T0) to 24 hours postoperatively (T2). Secondary outcomes include diaphragm thickening fraction (TFdi), diaphragm excursion, PaO₂/FiO₂ ratio, extubation time, and ICU/hospital length of stay. Lung and diaphragm ultrasonography will be performed by an assessor blinded to group allocation at three time points: preoperatively (T0), at end of surgery while intubated (T1), and at 24 hours postoperatively after extubation (T2).

• Study Type: Interventional
• Enrollment (Estimated): 154
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ebru GIRGIN DINC, M.D., DESAIC; Phone Number: 905446948852; Email: grgnebru@gmail.com

Study Locations

• Turkey (Türkiye)
  • Kartal
    • Istanbul, Kartal, Turkey (Türkiye), 34862
      • Kosuyolu Heart Training and Research Hospital

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Age ≥18 years
• Planned elective isolated on-pump coronary artery bypass graft (CABG) surgery
• ASA Physical Status Classification II-IV
• Written informed consent obtained
• Technically adequate acoustic window for lung and diaphragm ultrasonography

Exclusion Criteria:

• Emergency surgery
• Combined surgical procedures (e.g., valve repair/replacement + CABG)
• Preoperative requirement for invasive or non-invasive mechanical ventilation
• Known diaphragm paralysis or neuromuscular disease
• Severe COPD exacerbation or active pneumonia at time of surgery
• Body mass index ≥40 kg/m²
• Inability to obtain standard lung or diaphragm ultrasound images due to pleural effusion, thoracic deformity, or prior thoracic surgery

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: FCV (Flow-Controlled Ventilation); Intraoperative ventilation with a Flow-Controlled Ventilation device. Target tidal volume: 6-8 mL/kg ideal body weight (IBW). PEEP and peak airway pressure titrated to maximise dynamic compliance. Respiratory rate adjusted to maintain EtCO₂ 35-45 mmHg. FiO₂ targeted to SpO₂ ≥94%.	Procedure: Pressure-Controlled Ventilation (PCV); PCV is delivered using a standard anaesthesia workstation in pressure-controlled mode. Inspiratory pressure is set to achieve a tidal volume of 6-8 mL/kg ideal body weight. PEEP is titrated using the same compliance-guided algorithm applied in the FCV arm. Unlike FCV, the inspiratory flow profile is decelerating and PEEP and peak airway pressure are not independently optimised in a compliance-guided manner within the same ventilation mode
Active Comparator: PCV (Pressure-Controlled Ventilation); Intraoperative pressure-controlled ventilation. Inspiratory pressure adjusted to deliver a tidal volume of 6-8 mL/kg IBW. PEEP titrated to maximise dynamic compliance, using the same algorithm as the FCV group. Respiratory rate adjusted to maintain EtCO₂ 35-45 mmHg. FiO₂ targeted to SpO₂ ≥94%.	Procedure: Flow-Controlled Ventilation; FCV delivers tidal ventilation via a continuous triangular flow waveform, maintaining constant inspiratory and expiratory flow rates throughout the entire respiratory cycle. PEEP and peak airway pressure are titrated independently, guided by dynamic respiratory system compliance. Tidal volume target is 6-8 mL/kg ideal body weight. This ventilation modality is distinct from pressure-controlled and volume-controlled modes, which generate decelerating inspiratory flow profiles and do not allow simultaneous independent titration of PEEP and peak airway pressure based on compliance.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Total Lung Ultrasound Score (LUS)	Lung aeration assessed using a 12-zone bilateral ultrasonography protocol. Each zone scored 0-3 (0 = normal aeration with A-lines; 1 = multiple B-lines; 2 = coalescent B-lines; 3 = consolidation). Total score ranges from 0 to 36; higher scores indicate greater aeration loss	Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Diaphragm Thickening Fraction (TFdi)	Bilateral diaphragm thickening fraction measured via B-mode and M-mode ultrasonography at the zone of apposition using a linear probe (7-12 MHz). TFdi (%) = [(T_insp - T_exp) / T_exp] × 100.	Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)
Diaphragm Excursion	Bilateral inspiratory diaphragm dome displacement measured via M-mode ultrasonography using a convex probe (2-5 MHz) via subcostal approach.	Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)
PaO₂/FiO₂ Ratio	Ratio of arterial oxygen partial pressure to fractional inspired oxygen, calculated from arterial blood gas analysis.	Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)
Postoperative Pulmonary Complications	Composite of clinically significant pulmonary complications including radiologically confirmed atelectasis, pneumonia, and re-intubation, assessed according to pre-specified definitions.	Up to 30 days postoperatively

Collaborators and Investigators

• Sponsor: Koşuyolu Kartal Heart Training and Research Hospital
• Investigators: Principal Investigator: Ebru GIRGIN DINC, Koşuyolu Kartal Heart Training and Research Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): September 30, 2026
• Primary Completion (Estimated): September 30, 2028
• Study Completion (Estimated): December 30, 2028

Study Registration Dates

• First Submitted: August 30, 2026
• First Submitted That Met QC Criteria: August 30, 2026
• First Posted (Actual): September 2, 2026

Study Record Updates

• Last Update Posted (Actual): September 2, 2026
• Last Update Submitted That Met QC Criteria: August 30, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Cardiac Surgery; Cardiopulmonary Bypass; Point-of-Care Ultrasound; Lung Ultrasound; Diaphragm Ultrasonography; Lung-Protective Ventilation; Diaphragm Thickening Fraction; Diaphragm Excursion; Flow-Controlled Ventilation; Pressure-Controlled Ventilation; Perioperative Pulmonary Complications
• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Heart Diseases; Respiratory Tract Diseases; Lung Diseases; Respiration Disorders; Arteriosclerosis; Arterial Occlusive Diseases; Coronary Disease; Myocardial Ischemia; Respiratory Insufficiency; Pulmonary Atelectasis; Coronary Artery Disease
• Other Study ID Numbers: FCV-PCV-DTI-LUS

Drug and device information, study documents

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