Temporal Dynamics and Clinical Relevance of Oscillatory Amplitude Variability During High‐Frequency Oscillatory Ventilation With Volume Guarantee in Preterm Infants

ABSTRACT Objective To characterise temporal dynamics, variance structure, determinants, and predictive relevance of oscillatory amplitude variability during high‐frequency oscillatory ventilation with volume guarantee (HFOV‐VG) in preterm infants. Methods Single‐centre retrospective cohort study using minute‐level ventilator data collected during the first 72 h of HFOV‐VG. Amplitude variability was quantified using standard deviation, coefficient of variation (CV), and root mean square of successive differences (RMSSD). Temporal patterns, variance decomposition, and determinants of variability were assessed using mixed‐effects modelling separating within‐ and between‐infant effects. Predictive performance for death before discharge or moderate‐to‐severe bronchopulmonary dysplasia was evaluated using receiver operating characteristic analysis. Results A total of 237,790 measurements from 60 infants were analysed. Amplitude CV declined from 0.122 (0.072–0.160) at 0–6 h to 0.063 (0.035–0.106) at 48–72 h, while RMSSD decreased from 2.10 (1.22–2.69) to 1.13 (0.64–1.94). Variability was predominantly within‐infant (ICC 0.246–0.282), whereas mean amplitude, VThf/kg, and frequency were predominantly between‐infant. Within‐infant increases in oscillatory frequency were associated with higher variability, whereas increases in mean airway pressure and time from HFOV initiation were associated with lower variability. The composite outcome occurred in 47/60 infants. Early oscillatory amplitude variability demonstrated moderate discrimination (AUC 0.72, 95% CI 0.55–0.86), with an AUC of 0.82 (95% CI 0.66–0.95) when combined with oscillatory frequency and weight‐normalised DCO 2 . Conclusions Oscillatory amplitude variability during HFOV‐VG reflects dynamic ventilator–lung interactions. Its association with adverse respiratory outcome is hypothesis‐generating and requires validation in larger independent cohorts.