365 - Comparing Functional Lung Space Before and After Extubation Using Electrical Impedance Tomography

Publication Number: 365.4225

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

Background: Prolonged intubation with invasive ventilation of preterm infants carries risk of airway trauma, lung injury and increased sedation use. Predicting extubation readiness is critical to balance ongoing risks and benefits of invasive ventilation. Currently, physical exam, x-rays, ventilator settings and clinical judgement determine extubation readiness. However, many infants still fail or may be able to extubate sooner. Electrical impedance tomography (EIT) is a non-invasive tool that may support this decision point by monitoring and visualizing respiratory physiology parameters via bioimpedance variation.

Objective: Our objective was to determine the relationship between changes in end inspiratory (EILI) and end expiratory lung impedance (EELI), tidal variation impedance (TVi), center of ventilation (CoV), and functional lung space with extubation using EIT (Table 1). We hypothesized a decrease in EELI and functional lung space would occur after extubation.

Design/Methods: This IRB-approved, prospective, observational study examined intubated infants of corrected gestational age >26 weeks or birthweight > 750 g. EIT data from individual breaths over a 15-minute period before and after extubation were obtained, averaged, and compared. The clinician decided the mode of support that infants extubated to. Ibex R1 software (Sentec) was used for data analysis, with paired t-test to compare EIT parameters before and after extubation.

Results: We enrolled 10 infants intubated for respiratory failure. Infants were extubated to a variety of modes including low flow nasal canula (1), high flow nasal canula (2), continuous positive airway pressure (2), and non-invasive positive pressure (5). When applicable, positive end expiratory pressure ranged from 6-10 after extubation. EELI decreased after extubation by 3% (p < 0.05) with no significant change in EILI. TVi increased after extubation by 25% (p < 0.05) and had greater variability. There was no change in functional lung space or center of ventilation. See Figure 1 for EIT changes from a representative infant during extubation.

Conclusion(s): The observed changes in EIT parameters indicate that functional residual capacity decreased, and tidal volume increased after extubation in this sample. Further studies are necessary to determine optimal timing of extubation in infants with respiratory failure. EIT may help characterize physiologic lung parameters to inform extubation readiness.

Table 1
Explanation of EIT parameters and their clinical correlates.

Figure 1
EIT changes from a representative infant during extubation.