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Background Bronchopulmonary dysplasia (BPD) is one of the most common complications of prematurity. While severity of BPD is defined by need and type of respiratory support at 36 weeks, it does not distinguish between endotypes of disease. Recent studies suggest that infants with severe BPD have parenchymal, airway and pulmonary vascular disease. Determining the BPD phenotype could help guide future individualized therapy. Oscillometry is a bedside tool that measures the resistance of the airways and the reactance of the pulmonary parenchyma. Normative values of oscillometry need to be established to serve as a comparison prior to establishing oscillometry characteristics of the different types of BPD. This study aims to determine normative values of oscillometry for neonates without respiratory disease. Methods Neonates born at a gestational age of ≥ 36 weeks and in room air were recruited at < 29 days of age. Exclusion criteria included current supplemental oxygen or positive pressure support. Neonates were tested at their bedside while asleep, supine, with head and neck in neutral positioning. The Tremoflo N-100 oscillometry device was applied to the neonate’s face with a simple face mask and 2Liters/min bias flow was introduced into the system. Neonates were breathing spontaneously while the oscillometry device introduced 6 different frequencies (7 Hz, 13 Hz, 20 Hz, 29 Hz and 35 Hz) into the neonate’s respiratory system. The device then determined the reactance and resistance of the respiratory system at each frequency. Neonates were tested 3 times, in 30 second intervals, with a few minutes rest allowed between each test. Results Eight patients have been recruited to participate at this time. The participant group has an average gestational age of 38.1 weeks, average birth weight of 3176 grams and average birth length of 50.9 cm. Preliminary data demonstrates consistent reactance values at 37, 29 and 20 Hz, with reactance spacing out some as the frequency decreases. The measured resistance at these frequencies (37 and 29 Hz) is also clustered, although the resistance values remain consistent at 13 Hz as well. The resistance is greatest at the lowest frequency of 7 Hz. Two test subjects have outlying data, but this does not appear to be related to gestational age or size of the subject. There was no difference in reactance or resistance based on gestational age, birth weight or birth length. Discussion Our findings are consistent with previous studies that have demonstrated resistance in the airways is highest at the lowest frequency of 7 Hz and resistance decreases with increasing frequency (Klinger et al.) Reactance is most negative at the lowest frequencies and increases with increasing frequency. Oscillometry provides consistent and reliable data for evaluating the pulmonary function of term, healthy newborns.




Presented at the 2023 Children's Hospital Neonatal Consortium Annual Symposium; Denver, CO; Oct 11-13, 2023 and at the American Academy of Pediatric 2023 National Conference; Washington, D.C.; Oct 20-24, 2023.

Oscillometry in Term Neonates without Respiratory Disease

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