Coronary Artery Disease, Postoperative Pulmonary Complications, Pulmonary Atelectasis, Postoperative, Diaphragm Dysfunction, Respiratory Insufficiency
Conditions
Keywords
Flow-Controlled Ventilation, Pressure-Controlled Ventilation, Lung Ultrasound, Diaphragm Ultrasonography, Diaphragm Excursion, Diaphragm Thickening Fraction, Lung-Protective Ventilation, Point-of-Care Ultrasound, Perioperative Pulmonary Complications, Cardiopulmonary Bypass, Cardiac Surgery
Brief summary
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).
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).
Interventions
PROCEDUREFlow-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.
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
Sponsors
Koşuyolu Kartal Heart Training and Research Hospital
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
Complete blinding of the anaesthesia care provider is not achievable given the distinct operational characteristics of the FCV device versus a standard ventilator in PCV mode. Accordingly, a single-blind (outcomes assessor-blinded) design is employed. A dedicated assessor, unaware of group assignment, performs all lung and diaphragm ultrasound examinations at each time point (T0, T1, T2) and scores the images offline using coded identifiers. The assessor has no access to the ventilator display, the anaesthesia record, or any clinical documentation that could reveal group allocation. To quantify inter-rater reliability, the first ten subjects are independently scored by two blinded assessors; disagreements exceeding one point per zone are resolved by consensus before proceeding.
Intervention model description
This is a single-centre, prospective, randomised, parallel-group controlled trial comparing two intraoperative ventilation strategies - Flow-Controlled Ventilation (FCV) and Pressure-Controlled Ventilation (PCV) - in adults undergoing elective isolated on-pump coronary artery bypass graft (CABG) surgery. A parallel-group design was selected because the two ventilation modes are mutually exclusive within a single surgical procedure; crossover is not feasible.
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Total Lung Ultrasound Score (LUS) | 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
| Measure | Time frame | Description |
|---|---|---|
| Diaphragm Thickening Fraction (TFdi) | 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. |
| Diaphragm Excursion | 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. |
| PaO₂/FiO₂ Ratio | 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. |
| Postoperative Pulmonary Complications | 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. |
Countries
Turkey (Türkiye)
Contacts
CONTACTEbru GIRGIN DINC, M.D., DESAIC
PRINCIPAL_INVESTIGATOREbru GIRGIN DINC
Koşuyolu Kartal Heart Training and Research Hospital
Outcome results
None listed