Ventilatory efficiency during high-frequency oscillatory ventilation with volume guarantee in preterm infants

This study aims to evaluate the relationship between ventilator-derived carbon dioxide clearance and arterial CO 2 elimination during high-frequency oscillatory ventilation with volume guarantee (HFOV-VG), and to examine determinants and clinical relevance of ventilatory efficiency. In this cohort study, preterm infants less than 30 weeks of gestation receiving HFOV-VG were studied during the first 72 h after birth. Minute-level ventilator data were paired with arterial blood gases. Ventilatory efficiency was defined as weight-normalised DCO 2 divided by arterial PCO 2 . Temporal patterns and determinants were analysed using generalised estimating equations. The clinical outcome was death or moderate-to-severe bronchopulmonary dysplasia (BPD). A total of 185,018 ventilator observations and 595 paired ventilator–blood gas measurements from 60 infants were analysed. Arterial PCO 2 remained stable (50 [43–56] mmHg) despite wide variation in DCO 2 (34.6 [27.1–47.8]). Ventilatory efficiency varied between infants (0.72 [0.55–0.98]) and demonstrated a temporal pattern, decreasing from 0.77 (0.61–0.90) at 0–6 h to 0.65 (0.45–0.80) at 6–12 h and increasing to 0.76 (0.56–1.07) at 24–48 h. Higher efficiency was associated with higher oscillatory frequency ( p < 0.001). Death or moderate-to-severe BPD occurred in 85.0%, 70.0%, and 45.0% across low, intermediate-, and high-efficiency tertiles, respectively. Ventilatory efficiency demonstrated moderate discrimination for the composite outcome (AUC 0.69), improving to 0.76 with FiO 2 and mean airway pressure. Conclusion : During HFOV-VG, ventilator-derived CO 2 clearance showed limited correspondence with arterial PCO 2 . Ventilatory efficiency had moderate discrimination for adverse respiratory outcomes. What is Known: • During high-frequency oscillatory ventilation, ventilator-derived indices such as oscillatory tidal volume and DCO2 are commonly used to guide carbon dioxide clearance. • The relationship between ventilator-derived carbon dioxide transport and effective arterial CO2 elimination during HFOV with volume guarantee remains incompletely understood. What is New: • Ventilatory efficiency provides a physiological measure integrating ventilator-derived carbon dioxide transport and arterial CO2 elimination during HFOV with volume guarantee, a relationship that is not routinely evaluated in clinical practice. • Ventilatory efficiency demonstrated modest discrimination for death or moderate-to-severe bronchopulmonary dysplasia, with discrimination improving when combined with markers of respiratory support intensity.