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

N/ANot Yet RecruitingNCT07800741

Koşuyolu Kartal Heart Training and Research Hospital154 enrolled

Overview

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).

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

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

TRIPLE

Enrollment

154

Conditions

Coronary Artery Disease

Interventions

Flow-Controlled VentilationPROCEDURE

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

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

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

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

Secondary Outcomes

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.

Time frame: 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.

Time frame: 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.

Time frame: 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.

Time frame: Up to 30 days postoperatively

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

Overview

Conditions

Interventions

Eligibility

Locations (1)

Outcomes

Primary Outcomes

Secondary Outcomes

Central Contacts