363 - Non-invasive Oscillometry to Quantify the Severity of Lung Disease in Preterm Infants

Publication Number: 363.5902

Colm P. Travers, UAB, Birmingham, AL, United States; Viral Jain, University of Alabama School of Medicine, Birmingham, AL, United States; Kimberly Armstead, University of Alabama School of Medicine, Birmingham, AL, United States; Waldemar Carlo, UAB School of Medicine, Birmingham, AL, United States; Namasivayam Ambalavanan, University of Alabama School of Medicine, Birmingham, AL, United States

Background: Impulse oscillometry (iOS) is a non-invasive method to assess respiratory disease widely used in older children and adults. In a pilot study we previously showed that iOS may be able to measure the nature and magnitude of lung disease in preterm infants.

Objective: To test the hypothesis that differences in pulmonary mechanics among preterm infants with and without lung disease can be objectively measured using iOS.

Design/Methods: Single center prospective observational cohort study enrolling preterm infants 22-34 weeks’ gestation with and without lung disease admitted to the neonatal intensive care unit and healthy term-late preterm infants (≥ 35 weeks’ gestation, controls) without lung disease admitted to the newborn nursery. After obtaining informed consent, we measured pulmonary mechanics using iOS at discharge or 40 weeks’ PMA (whichever occurred first) using the Tremoflo N-100 Airwave Oscillometry device (Thorasys, Montreal). Two sets of tests including ≥3 measurements using coefficient of variation < 20% within a 15% agreement threshold were obtained in the supine neutral head position. The primary analysis compared differences in the mean area under the reactance curve (AX). Secondary analyses compared difference in resistance at 7 Hz (R7), the difference between R7 and resistance at 19Hz (R7-19), and reactance at 7Hz (X7). Data were analyzed using logistic regression adjusted for weight at testing, sex, and multiple testing using the Bonferroni method.

Results: We included 600 infants (145 controls, 94 preterm without lung disease, 228 with respiratory distress syndrome (RDS) but no bronchopulmonary dysplasia (BPD), and 133 with BPD). As expected, the mean (SD) gestational age and birth weight differed between groups (Table 1). AX was highest among infants with BPD suggesting stiffer lungs, followed by infants with RDS but no BPD, preterm infants without RDS or BPD, and controls (p < 0.05 for all comparisons, Table 2). Overall, AX decreased with increasing gestational age and differed by lung disease status (Figure 1). R7-19 was also highest among infants with BPD suggesting heterogeneous peripheral airway disease, followed by infants with RDS but no BPD, preterm infants without RDS or BPD, and controls (p < 0.05 for all comparisons, Table 2). X7 and R7 values were highest in infants with BPD and lowest in controls.

Conclusion(s): Impulse oscillometry can objectively quantify the type and severity of lung disease in preterm infants. Abnormal lung mechanics in preterm infants with lung disease are characterized by increased stiffness and heterogeneous peripheral airways disease.

Table 1
Baseline characteristics between infants with and without lung disease who completed oscillometry testing before discharge of 40 weeks’ PMA.

Table 2
Pulmonary mechanics in healthy infants, preterm infants without lung disease, preterm infants with RDS, and preterm infants with BPD adjusted for weight at testing, sex, and Bonferroni correction. AX = area under the reactance curve. X7 = reactance at 7Hz, R7 = resistance at 7 Hz, R7-19 = the difference between R7 and resistance at 19Hz, RDS = respiratory distress syndrome, BPD = bronchopulmonary dysplasia.

Figure 1
Scatter plot¬ with regression lines for area under the reactance curve (AX) among preterm infants by gestational age and BPD status.