Effect of Positive End-Expiratory Pressure on Cardiac Index and Right Ventricular Performance in Ventilated Children Post-Cardiac Surgery

OBJECTIVE: Lower positive end-expiratory pressure (PEEP) is commonly suggested in congenital heart disease (CHD) patients to prevent hemodynamic impairment and right ventricular (RV) dysfunction. We sought to study the effect of different levels of PEEP on cardiac index, lung mechanics, and RV function in subjects after cardiac surgery. DESIGN: Prospective, single-center physiology study conducted in a tertiary pediatric cardiac ICU between November 2023 and July 2024. SETTING: Operating room (OR) and cardiac ICU (CICU). PATIENTS: Subjects younger than 5 years post-cardiac surgery for CHD. INTERVENTIONS: Four consecutive PEEP levels: baseline (PEEPstart), high PEEP (baseline plus 4 cm H 2 O; PEEPhigh), low PEEP (baseline minus 4 cm H 2 O; PEEPlow), and return to baseline (PEEPend). MEASUREMENTS: In 58 subjects, cardiac index and RV function, static (Cstat) and dynamic compliance, and transpulmonary pressures were measured at each PEEP level and with constant driving pressure. Of these subjects, 81.0% underwent surgery with cardiopulmonary bypass (CPB). The median age was 4.9 months, and 55% of subjects were male. The mean baseline PEEP was 6.2 cm H₂O ( sd 1.4), the mean PEEPhigh was 10.2 cm H₂O ( sd 1.4), and the mean PEEPlow was 3.3 cm H₂O ( sd 0.7). MAIN RESULTS: Overall, cardiac index and RV performance increased significantly with PEEPhigh ( p < 0.01). Cardiac index decreased in 7 of 58 patients (12%)with PEEPhigh and in 18 of 58 patients (31%) with PEEPlow. Directional change in measures of RV performance and Cstat over time was generally concordant; with manipulation of PEEP, both improved or worsened together, independent of the underlying lesion. Sensitivity analyses showed that the results remained consistent regardless of the location of the measurement (OR vs. CICU), whether inhaled nitric oxide or milrinone was used, whether RV outflow tract obstruction was present, and whether CPB was used. CONCLUSIONS: In children with CHD who underwent biventricular repair, cardiac index, RV function, and Cstat generally improved with higher PEEP, indicating pulmonary recruitment. Changes in cardiac performance and Cstat were closely related, with both improving or worsening together with manipulation of PEEP. This study supports the use of PEEP to optimize lung volume and cardiopulmonary interactions after cardiac surgery.