Mechanical Power and Pulmonary Complications in CABG Surgery

This single-center prospective observational study enrolls adult patients undergoing elective first-time isolated coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass (CPB).

Mechanical power (MP) will be calculated as: MP = 0.098 × RR

× VT × [PIP - 0.5 × (Pplat - PEEP)], normalized to predicted body weight (norMP = MP/PBW). Male PBW (kg) = 50 + 0.91 × [height (cm) - 152.4]; female PBW (kg) = 45.5 + 0.91 × [height (cm) - 152.4]. Driving pressure (DP) = Pplat - PEEP.

Ventilatory parameters (VT, RR, peak pressure, plateau pressure, PEEP, FiO2, EtCO2) and arterial blood gases (PaO2/FiO2, PaCO2, lactate) will be recorded at four standardized time points: T1 (post-intubation), T2 (post- sternotomy), T3 (pre-bypass), and T4 (post-bypass). No additional interventions beyond standard clinical care will be applied.

Postoperative outcomes including atelectasis, pneumonia, pleural effusion, prolonged oxygen requirement, need for non-invasive ventilation, re-intubation, duration of mechanical ventilation, and ICU length of stay will be assessed within the first 48 hours.

Sample size: 110 patients (α=0.05, power=80%, expected PPC incidence 35% vs 65% in low vs high MP groups, 20% dropout allowance). Statistical analysis will include Mann-Whitney U or t-test, chi-square or Fisher exact test, and logistic regression. Significance: p<0.05 (two-tailed).

Inclusion criteria

• Age 18 years or older
• Scheduled for elective, first-time isolated CABG surgery
• Use of cardiopulmonary bypass (CPB)
• Intraoperative mechanical ventilation applied under general anesthesia with recordable ventilator data
• Provision of written informed consent

Exclusion criteria

• Emergency cardiac surgery
• Off-pump CABG (without CPB)
• Preoperative requirement for invasive mechanical ventilation
• Advanced chronic lung disease
• Incomplete or unreliable intraoperative ventilatory data
• Intraoperative use of advanced non-standard support (ECMO)