Objectives To assess the work of breathing at different levels of volume targeting in prematurely born infants with evolving or established bronchopulmonary dysplasia (BPD).

Design Randomised crossover study.

Setting Tertiary neonatal intensive care unit.

Patients Eighteen infants born at <32 weeks gestation who remained ventilated at or beyond 1 week after birth, that is, they had evolving or established BPD.

Interventions Infants received ventilation at volume targeting levels of 4, 5, 6 and 7 mL/kg each for 20 minutes, the levels were delivered in random order. Baseline ventilation (without volume targeting) was delivered for 20 minutes between each epoch of volume-targeting.

Main outcome measures Pressure-time product of the diaphragm (PTPdi), a measure of the work of breathing, at different levels of volume targeting.

Results The 18 infants had a median gestational age of 26 (range 24–30) weeks and were studied at a median of 18 (range 7–60) days. The mean PTPdi was higher at 4 mL/kg than at baseline, 5 mL/kg, 6 mL/kg and 7 mL/kg (all P≤0.001). The mean PTPdi was higher at 5 mL/kg than at 6 mL/kg (P=0.008) and 7 mL/kg (P<0.001) and higher at 6 mL/kg than 7 mL/kg (P=0.003). Only at 7 mL/kg was the PTPdi significantly lower than at baseline (P=0.001).

Conclusions Only a tidal volume target of 7 mL/kg reduced the work of breathing below the baseline and may be more appropriate for infants with evolving or established BPD who remained ventilator dependent at or beyond 7 days of age.