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NCT Number: NCT07800741

Flow-Controlled vs. Pressure-Controlled Ventilation in CABG: Effects on Lung Aeration and Diaphragm Function

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).

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Key information

Conditions

Coronary Artery Disease Arterial Occlusive Diseases Arteriosclerosis Cardiovascular Diseases Coronary Disease Diaphragm Dysfunction Heart Diseases Lung Diseases Myocardial Ischemia Postoperative Pulmonary Complications Pulmonary Atelectasis Pulmonary Atelectasis, Postoperative Respiration Disorders Respiratory Insufficiency Respiratory Tract Diseases Vascular Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Kosuyolu Heart Training and Research Hospital

Istanbul, Kartal, 34862, Turkey (Türkiye)

About this study

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).

Who can participate

Healthy volunteers accepted: No

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

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

Treatment and study plan

Flow-Controlled Ventilation

Procedure

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.

Pressure-Controlled Ventilation (PCV)

Procedure

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

Primary outcomes

  1. Total Lung Ultrasound Score (LUS)

    Time frame: Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)

    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

Secondary outcomes

  1. Diaphragm Thickening Fraction (TFdi)

    Time frame: Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)

    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.

  2. Diaphragm Excursion

    Time frame: Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)

    Bilateral inspiratory diaphragm dome displacement measured via M-mode ultrasonography using a convex probe (2-5 MHz) via subcostal approach.

  3. PaO₂/FiO₂ Ratio

    Time frame: Preoperatively (T0), within 30 minutes of sternal closure while intubated (T1), and 24 hours postoperatively after extubation (T2)

    Ratio of arterial oxygen partial pressure to fractional inspired oxygen, calculated from arterial blood gas analysis.

  4. Postoperative Pulmonary Complications

    Time frame: Up to 30 days postoperatively

    Composite of clinically significant pulmonary complications including radiologically confirmed atelectasis, pneumonia, and re-intubation, assessed according to pre-specified definitions.

Study contacts

Contact information is provided by the study sponsor or research team.

Ebru GIRGIN DINC, M.D., DESAIC

CONTACT

[email protected]

905446948852

Sponsors and collaborators

Lead sponsor

Koşuyolu Kartal Heart Training and Research Hospital

Other

Registry information

Official study title

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

Acronym: FCV-PCV-DTI-LU

Important dates

Study start
2026
Primary completion
2028
Study completion
2028
First posted
Sep 2, 2026
Registry last updated
Sep 2, 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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