Combining lung ultrasound and oscillatory mechanics for assessing lung disease in very preterm infants.

Background: We investigated whether combining lung ultrasound scores (LUSs) and respiratory system reactance (Xrs) measured by respiratory oscillometry explains the severity of lung disease better than individual parameters alone.

Methods: We performed a prospective observational study in very preterm infants. Forced oscillations (10 Hz) were applied using a neonatal mechanical ventilator (Fabian HFOi, Vyaire). We used the simultaneous respiratory severity score (RSS = mean airway pressure × FIO) as a primary outcome. We built linear mixed-effect models to assess the relationship between Xrs z-score, LUS and RSS and compared nested models using the likelihood ratio test (LRT).

Results: We enrolled 61 infants (median (Q1, Q3) gestational age = 30.00 (26.86, 31.00) weeks) and performed 243 measurements at a postnatal age of 26 (13, 41) days and postmenstrual age of 33.14 (30.46, 35.86) weeks. Xrs z-score and LUS were independently associated with simultaneous RSS (p < 0.001 for both). The model including Xrs and LUS explained the RSS significantly better than Xrs (p value LRT < 0.001) or LUS alone (p value LRT < 0.001).

Conclusions: Combining LUS and Xrs z-score explains the severity of lung disease better than each parameter alone and has the potential to improve the understanding of the underlying pathophysiology.

Impact: Combining respiratory system reactance by oscillometry and lung ultrasound score explains the respiratory support requirement (e.g., proxy of the severity of lung disease) significantly better than each parameter alone. We assessed the relationship between lung ultrasound and respiratory system reactance in very preterm infants for the first time. Combining respiratory oscillometry and lung ultrasound has the potential to improve the understanding of respiratory pathophysiology.