Effect of PEEP on lung aeration in pediatric patients after cardiac surgery: a CT-Based study

Background

Loss of lung aeration is frequently observed in adult patients following cardiac surgery with cardiopulmonary bypass. Yet, in children, changes in lung aeration following surgical repair of congenital heart defects, and the effects of Positive End-Expiratory Pressure (PEEP), remain uncertain.

Methods

Changes in lung aeration were investigated using volumetric computed tomography in 12 children with congenital acianogenic heart diseases and increased pulmonary flow who underwent total surgical repair under cardiopulmonary bypass. Computed tomography of the lungs was obtained preoperatively during spontaneous breathing and postoperatively during mechanical ventilation with positive end-expiratory pressure of 0, 5 and 10 cm H₂O. Gas and tissue lung volume and mass, as well non-aerated, poorly aerated and normally aerated lung compartments were measured.

Results

Median age of patients was 18.3 months, (4 to 24 months), weight was 9.3 ± 2.3 kg. Cardiopulmonary bypass duration was 77 ± 26 minutes. Preoperatively, pulmonary volume was 545 mL (237‒753 mL), whereby tissue and gas volumes were 48.4% (41.7%‒59.6%), and 51.6% (40.4%‒58.3%), respectively. Non-aerated and normally aerated compartments accounted for 15% and 47.9% of lung tissue, respectively. Postoperatively, at zero PEEP, the non-aerated compartment increased to 27%, while normally-aerated compared decreased to 38.5%. Stepwise PEEP application restored normally aerated lung volume to preoperative levels but did not significantly reduce non-aerated parenchyma.

Conclusion

Loss of lung aeration was pronounced after surgical correction of congenital heart defects. PEEP up to 10 cm H₂O restored gas volume but failed to recruit the collapsed parenchyma. Ethical Approval CAPPesq n° 854/01.