The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

SURVIVAL AND IMPROVEMENT OF PHYSIOLOGIC DEAD-SPACE DURING ECMO IN CHILDREN WITH CONGENITAL DIAPHRAGMATIC HERNIA.

Craig D. Smallwood1, Erin Libbey1, Nancy Craig1, Jay Wilson2,3; 1Respiratory Care, Boston Children’s Hospital, Boston, MA; 2Surgery, Boston Children’s Hospital, Boston, MA; 3Harvard Medical School, Boston, MA

INTRODUCTION: Congenital diaphragmatic hernia (CDH) is a rare birth defect that is characterized by mal-development of the diaphragm and the presence of abdominal viscera in the thorax. CDH is associated with varying degrees of pulmonary hypoplasia and persistent pulmonary hypertension. Despite therapeutic interventions such as inhaled nitric oxide (iNO) and extracorporeal membrane oxygenation (ECMO), mortality remains high. We sought to determine the relationship between the physiologic dead-space fraction (Vd/Vt) and survival in infants with CDH requiring ECMO. METHODS: A retrospective review of all patients with CDH who required ECMO from September 2006 to September 2011 was conducted. Patient demographics, side of defect, survival, use of iNO, age at cannulation and type of ECMO support were recorded. Vd/Vt was calculated utilizing the Enghoff modification of the Bohr equation. PaCO2 was obtained from an indwelling arterial catheter and mixed expired CO2 was measured using a commercially available mainstream capnograph. All patients were cycled; whereby the patient was transiently separated from the ECMO circuit. Vd/Vt was obtained for the initial and final cycle during ECMO support. Data was recorded using MS Excel and statistical analysis was performed utilizing Prism Graphpad. The Wilcoxon signed rank test was used to assess the difference between initial and final cycle Vd/Vt measurements in the survivor and non-survivor groups. RESULTS: Twenty patients (n=14 male) were included in the analysis. The age at cannulation (mean±SD) and was 2.3 ± 4.6 days and the weight was 3.0 ± 0.6 kg. Sixteen (80%) patients survived to ICU discharge. Eighteen patients had left sided defects, 20 required veno-arterial ECMO and all received iNO. No relationship was observed between Vd/Vt and side of defect, iNO usage or type of ECMO support. Survivors exhibited a statistically significant decrease in Vd/Vt from 0.70 to 0.65 (P = 0.0331) during their ECMO course. There was no significant change in Vd/Vt of the non-survivors (see figure: horizontal bars = mean, whiskers = standard error). CONCLUSIONS: An improvement in Vd/Vt during ECMO support was associated with survival. The decreased Vd/Vt may reflect an improvement in pulmonary performance and specifically an improvement in pulmonary hypertension. Serial measurement of Vd/Vt in patients with CDH may prove to be useful in determining severity of disease and likelihood of survival. Sponsored Research - None