331 - Non-invasive Oscillometry to Measure the Effects of Furosemide on Lung Mechanics in Extremely Preterm Infants
Sunday, April 30, 2023
3:30 PM – 6:00 PM ET
Poster Number: 331 Publication Number: 331.345
Colm P. Travers, University of Alabama School of Medicine, Birmingham, AL, United States; Waldemar A. Carlo, University of Alabama School of Medicine, Birmingham, AL, United States; Kimberly Armstead, University of Alabama School of Medicine, Birmingham, AL, United States; Namasivayam Ambalavanan, University of Alabama School of Medicine, Birmingham, AL, United States
Assistant professor University of Alabama School of Medicine Birmingham, Alabama, United States
Background: Many preterm infants receive furosemide to improve lung mechanics based on data from relatively invasive pulmonary function tests. Non-invasive oscillometry measures lung resistance (R) and reactance (X), a measure of pulmonary elasticity and inertance, at the bedside without sedation. Objective: We hypothesized that non-invasive oscillometry would reproducibly measure the effects of furosemide on lung mechanics in preterm infants. Design/Methods: Single-center prospective pre-post study including preterm infants ≥ 22w 0d off positive pressure respiratory support exposed to furosemide. Non-invasive oscillometry was performed before, 1-2 hours after, and 24 hours after clinically-indicated furosemide exposure using a Tremoflo N-100 (Thorasys, Montreal). The primary outcome was the change in the area under the reactance curve at 1-2 hours after treatment (AX). Secondary outcomes included reactance at 7 Hz (X7), resistance at 7Hz (R7), and the difference in resistance between 7Hz and 19Hz (R7-19) at 1-2 hours and 24 hours after treatment. A sample of 30 infants was required to detect a 250 cmH2O.s/L or 20% decrease (1030 cmH2O.s/L pre- vs 825 cmH2O.s/L post-treatment) in AX assuming a standard deviation of 320 cmH2O.s/L, correlation of 0.7 between pre- and post-treatment values, power of 90%, α of 5%, and approximately 10% attrition rate for inadequate/incomplete testing. Results were analyzed by paired t-tests. Results: We tested 30 infants with a mean ± SD gestational age of 25w 6d ± 2w 1d and birth weight of 733 ± 205 grams on postnatal day 79 ± 33 from May 2021 to September 2022. Testing was complete in 28/30 (93.3%) infants and the intra-infant variability for each test session was excellent (R=0.92; R2=0.85; p< 0.001). AX decreased from 751 ± 261 cmH2O.s/L before treatment to 644 ± 246 cmH2O.s/L (mean difference, SEM, 107 ± 40; 95% CI, 24-190; p=0.01) at 1-2 hours and 660 ± 272 cmH2O.s/L (p=0.11) at 24 hours after treatment. X7 improved from -56 ± 22 cmH2O.s/L to -46 ± 18 cmH2O.s/L (p=0.01) at 1-2 hours but the difference was not significant at 24 hours (-51 ± 23 cmH2O.s/L; p=0.18). R7 decreased from 57 ± 15 cmH2O.s/L before treatment to 51 ± 15 cmH2O.s/L at 1-2 hours (p=0.02) and 52 ± 12 cmH2O.s/L (p=0.05) 24 hours after treatment. R7-19 improved from 26 ± 10 cmH2O.s/L before treatment to 22 ± 10 cmH2O.s/L (p=0.046) at 1-2 hours and 22 ± 8 cmH2O.s/L (p=0.03) at 24 hours. There were individual differences in the response to furosemide (Figure 1).
Conclusion(s): In preterm infants off positive pressure support, furosemide improved lung mechanics measured using non-invasive oscillometry.
