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).
Age ≥18 years
Planned elective isolated on-pump coronary artery bypass graft (CABG) surgery
ASA Physical Status Classification II-IV
Written informed consent obtained
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
Parallel
Flow-Controlled Ventilation
Procedure/SurgeryFCV 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/SurgeryPCV 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
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
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.
Diaphragm Excursion
Bilateral inspiratory diaphragm dome displacement measured via M-mode ultrasonography using a convex probe (2-5 MHz) via subcostal approach.
PaO₂/FiO₂ Ratio
Ratio of arterial oxygen partial pressure to fractional inspired oxygen, calculated from arterial blood gas analysis.
Postoperative Pulmonary Complications
Composite of clinically significant pulmonary complications including radiologically confirmed atelectasis, pneumonia, and re-intubation, assessed according to pre-specified definitions.
Click on the lead sponsor to view all of their trials.
This trial is not recruiting at the moment. You can still explore other options:
