Hilo Trial: A Comparative Study of High versus Low Tidal Volume in Very Low Birth Babies with Respiratory Distress Syndrome

Background  Preterm infants often require mechanical ventilation. Volume targeted ventilation has been shown to reduce both complications and the duration of required mechanical ventilation. The recommended tidal volumes vary from 4-8 mL/kg, but the optimal tidal volume remains elusive.  Aims and objectives  To compare volume ventilation at a lower (4-5 mL/kg) with a higher (7-8 mL/kg) tidal volume during volume guarantee ventilation (VG) of respiratory distress syndrome (RDS) in very preterm infants.  Methodology  The randomised trial was conducted at North Tees Hospital in North East England from 2013 to 2016. Babies <32 weeks’ gestation or <1500 grams birthweight requiring mechanical ventilation within 12 hours of life from RDS were included in the study. Babies were randomised to receive lower (4-5 mL/kg) or higher (7-8 mL/kg) tidal volume using Volume Guarantee (VG). The primary outcome was the time to achieve a 25% reduction from the initial peak inspiratory pressure (PIP). Secondary outcomes included the duration of mechanical ventilation, as well as respiratory and non-respiratory complications.  Results  Babies in both groups were similar at baseline with regard to maternal, demographic and clinical characteristics. There was no difference in the primary outcome of time difference to reach a 25% reduction in baseline peak pressure between the two groups. There were no differences in short term secondary outcomes (air leak, pulmonary haemorrhage, sepsis, IVH, NEC, PDA and ROP) or medium term complications (Bronchopulmonary Dysplasia at 28 days’ life and 36 weeks PMA, severity of Bronchopulmonary Dysplasia, amount of home oxygen, survival to discharge and survival without Bronchopulmonary Dysplasia at 36 weeks PMA). The minute volume, paCO2 or FIO2 requirements were not significantly different either.  Summary and conclusions  This trial did not find statistically significant differences between lower versus higher tidal volume delivery in a population of 70 infants with RDS. It is possible that both tidal volume ranges selected for study are at functional residual capacity and this might be one reason for negative results of the study.