Influence of Lung Volume Optimization Maneuver on Cardiac Output and Lung Mechanics in Children With Congenital Heart Disease

Cardiopulmonary bypass is associated with interruption of ventilation, leading to atelectasis, reduced end-expiratory lung volume, and increased pulmonary vascular resistance (PVR), which may impair right ventricular (RV) performance and overall cardiac output.

This study investigates whether a structured LVOM strategy can mitigate these effects by improving lung mechanics and cardiopulmonary interactions.

Specific Aims

Aim 1:

To quantify changes in hemodynamics and lung mechanics induced by LVOM under standardized postoperative (closed-chest) conditions.

Aim 2:

To compare individualized PEEP titration versus standard ventilation in terms of effects on hemodynamics and lung mechanics, while maintaining consistent tidal volume targets across groups.

Hypotheses

LVOM will improve lung mechanics and hemodynamic parameters. No significant between-group differences are expected prior to intervention. After PEEP titration, the intervention group will demonstrate superior cardiopulmonary function at moderate PEEP levels, reflecting the U-shaped relationship between lung volume and pulmonary vascular resistance (PVR).

Scientific Rationale

Cardiopulmonary bypass commonly results in atelectasis and loss of end-expiratory lung volume, contributing to increased PVR and RV afterload, with subsequent reduction in cardiac output.

Adult studies suggest that lung volume optimization through PEEP titration after CPB can improve cardiac index and RV performance. However, prospective pediatric data evaluating the interaction between ventilatory strategy, lung mechanics, and hemodynamics remain limited.

Given the central role of the right ventricle in coupling pulmonary and systemic circulation, optimizing lung volume may reduce RV afterload and improve overall cardiac performance.

Importantly, pulmonary vascular resistance follows a U-shaped relationship with lung volume, with increased resistance at both low (atelectasis) and high (overdistension) lung volumes. Individualized PEEP titration may therefore identify an optimal range that minimizes PVR while preserving hemodynamic stability.

This study addresses a critical gap by systematically evaluating cardiopulmonary interactions under contemporary ventilation strategies in pediatric cardiac surgery.