Work of breathing at different levels of volume-targeted ventilation in infants with congenital diaphragmatic hernia

Aim: Volume-targeted ventilation (VTV) compared to pressure-limited ventilation has been shown to have benefits in prematurely-born infants. VTV is used in infants with congenital diaphragmatic hernia (CDH), but the optimum target tidal volume in that population is not known. Methods: Infants with CDH were eligible for inclusion in the study after repair of the diaphragmatic defect. Written, informed parental consent was obtained. Target tidal volumes of 4, 5 and 6ml/kg were each delivered for 20 minute periods in a random order, with 20 minutes periods of baseline pressure-limited ventilation in between each epoch of VTV. A dual pressure transducer tipped catheter was used to measure oesophageal and gastric pressures and the pressure-time product of the diaphragm (PTPdi) was calculated at the end of each 20 minute period. Results: Seven infants with median gestational age 38 (range 37 – 41) weeks and birthweight 3202 (range 2880 – 3800) grams were studied at a median postnatal age of five (range 4 – 6) days. One infant had a right-sided defect and none had undergone fetal endoscopic tracheal occlusion therapy. The median PTPdi at baseline was 161 (range 112 – 217) cmH2O.sec/min. The PTPdi was significantly lower at 5 and 6 mls/kg than at 4ml/kg (134 and 132cmH2O.sec/min versus 198cmH2O.sec/min, p=0.001 and p=0.011). There were no significant differences between the PTPdi at 5ml/kg and 6ml/kg (p=1.0) or between the results at baseline and any of the levels of volume targeting. Conclusion: The results suggest that if VTV was to be used a target tidal volume of 5ml/kg might be most appropriate in infants with CDH.