711 - Characterizing lung function in congenital diaphragmatic hernia using electrical impedance tomography

Publication Number: 4695.711

Christopher Torsitano, University of Utah, Salt Lake City, UT, United States; Michelle J. Yang, University of Utah School of Medicine, Salt Lake City, UT, United States; Bradley A.. Yoder, University of Utah, Salt Lake City, UT, United States; Ariel Tarrell, University of Utah School of Medicine, Salt Lake City, UT, United States

Background: Congenital diaphragmatic hernia (CDH) presents challenges to ventilation due to asymmetric pulmonary hypoplasia. Better understanding of differential ventilation for the right and left lung may optimize respiratory management strategies, particularly as lung function is dynamic at different stages of growth and recovery over the hospitalization. Electrical impedance tomography (EIT ) measures end-expiratory lung impedance (EELI), tidal variation impedance (TVi), and center of ventilation (CoV) to describe underlying lung function. EIT may be an effective tool to appraise regional lung ventilation differences in congenital diaphragmatic hernia over time.

Objective: The objective was to determine changes in EELI, TVi, and CoV for the ipsilateral and contralateral lung in infants with CDH over their hospitalization. We hypothesized that EIT lung function parameters would increase and that the center of ventilation would shift towards the ipsilateral lung over time.

Design/Methods: This IRB-approved, prospective, observational study examined infants with CDH at four pre-defined points during their hospital stay. EIT data from individual breaths were measured over a 1-hour period prior to CDH repair, post-repair, 1-2 weeks post-repair , and near discharge. Ibex R1 software (Sentec) was used for data analysis. Student’s t-tests were used to compare EIT parameters for the lungs and to compare post-operative measurements to the pre-repair measurement.

Results: 18 infants with CDH were enrolled; 16 were left-sided and the mean observed:expected lung ratio was 37% (+/- 14%). 17 (94%) infants were on high frequency ventilation pre-repair and 14 (78%) were post-repair. All infants were on room air or low flow nasal canula at discharge. EELI near discharge significantly increased compared to pre-repair from 1585 to 1925 for the ipsilateral lung (p = 0.01) and 1644 to 2065 for the contralateral lung (p < 0.001). TVi increased near discharge compared to pre-repair measurements from 18 to 42 for the ipsilateral lung (p < 0.001) and from 36 to 69 for the contralateral lung (p = 0.003). TVi was significantly higher in the contralateral lung vs. the ipsilateral lung at all time points (Table 1). CoV did not change significantly (41% pre-repair to 43% near discharge, p = 0.3).

Conclusion(s): Lung volume and lung function improved for both the ipsilateral and contralateral lung over time during the hospitalization. EIT can trend evolution of regional lung function differences in CDH. Further studies are warranted to determine points of intervention using EIT in the natural course of CDH.