(206) Electrical Impedance Tomography to Evaluate Pediatric Lung Dysfunction After Cardiopulmonary Bypass

Introduction: Pulmonary complications are reported to occur in 10-15% of patients following cardiopulmonary bypass (CPB) and may arise from lung dysfunction or injury after CPB. Ventilators maneuvers and Electrical Impedance Tomography (EIT) can detect alterations in, and patterns of, lung dysfunction after CPB. Thus, we aimed to use EIT and standard ventilator maneuvers to assess change in lung function, before and after CPB, in the pediatric cardiac surgical population.

Methods: Patients < 18 years old undergoing CPB were recruited. In the OR, EIT was monitored pre CPB upon intubation and post CPB after chest closure. Volume-Control ventilation (VT 8 mL/Kg) was used during passive ventilation and Pressure-Control ventilation (to achieve VT 8 mL/Kg) was used during spontaneous ventilation. A low flow maneuver to detect airway closure was followed by positive end-expiratory pressure (PEEP) titration at 5, 7 and 9 cmH2O for 2 minutes each. Analysis included comparisons pre vs post CPB in respiratory mechanics, regional ventilation and compliance distribution, and changes in end-expiratory impedance (EELZ).

Results: As part of an ongoing feasibility study, 5 patients with a mean age of 5 months were enrolled. All patients were intubated in the OR; 4 were extubated in the OR and 1 was extubated on post-op day 1. Median duration of post-op respiratory support was 3 days and median maximum FiO2 deployed was 50%. So far, 3 patients with reliable EIT data were analyzed. Impedance compliance decreased post CPB by a mean of 49%, 45% and 42% on a PEEP of 5, 7 & 9, respectively. On regional analysis, the distribution of ventilation post CPB was noted to be preferentially posterior. Increases in EELZ with PEEP up-titration were an average of 60% less post CPB, indicating decreased recruitment.

Conclusions: Preliminary data demonstrates a notable decrease in lung compliance and lesser increase in EELZ (recruitment) following CPB as demonstrated via EIT. However, we are limited in drawing substantial conclusions given our current sample size. Next steps include additional patient recruitment (n=20), pixelated EIT data analysis via R, and determining the association between duration of CPB/surgery and loss of regional compliance.