Abstract

Aim
To evaluate whether mechanical ventilation during cardiopulmonary bypass (CPB) reduces postoperative pulmonary complications (PPCs) in adult cardiac surgery patients.

Method
We searched PubMed and Cochrane for randomized controlled trials (RCTs) comparing ventilation during CPB versus no ventilation in adults. Paediatric studies and post-hoc analyses were excluded. Two reviewers independently screened studies and extracted data, a third reviewer resolved conflicts. The primary outcome was composite PPCs. Secondary outcomes included reintubation, mortality, inflammatory markers, and oxygenation. Risk of bias was assessed using Cochrane RoB 2.0 tool. Meta-analysis was conducted using Review Manager (RevMan) 5.4 with random-effects modelling and I² statistics for heterogeneity assessment.

Results
Six RCTs (3,373 patients) were included. Mean age ranged from 52-69 years, BMI 22.6-29.7 kg/m², CPB time 69-128 minutes, and cross-clamp time 35-83 minutes. Positive trials used tidal volumes of 3-4 mL/kg with PEEP 5-8 cmH₂O; RCTs without PEEP showed no benefit. Two RCTs had low risk of bias, but four were analysed as moderate due to unclear outcome assessor blinding. Meta-analysis of PPCs (2,053 patients) showed significant benefit with ventilation (OR 0.74, 95% CI 0.60-0.92, P=0.006; I²=0%). Secondary outcomes analysed showed reduced reintubation (2.2% vs 5.1%), improved oxygenation (+60 mmHg), and lower incidence of pneumonia (3.6% vs 6.5%). Major limitations included unavailable full text for one trial, and heterogeneous outcome definitions with different primary endpoints.

Conclusions
Ventilation during CPB significantly reduces PPCs by 26%. Evidence supports protective ventilation (tidal volume 3-4 mL/kg with PEEP 5-8 cmH₂O ); PEEP appears essential for achieving this outcome.