Dead-space washout by split-flow ventilation. A new method to reduce ventilation needs in premature infants.

OBJECTIVE

Chronic lung disease caused by volutrauma is one of the most important consequences of preterm delivery. In this pilot study a new method is presented that consists of flushing part of the dead space with fresh gas in order to reduce high tidal volumes, the chief cause of volutrauma. The aim of the study was to evaluate if the new method could reduce ventilatory effort in preterm infants by diminishing dead space.

DESIGN AND SETTING

In split-flow ventilation, gas required for dead-space washout is split off from the regular ventilation circuit. The split flow bypasses the apparatus dead space and fills it retrogradely with fresh breathing gas, mainly in the pause between exhalation and inspiration. The mean per-minute ventilation and ventilation index after 12 h of conventional ventilation were compared with corresponding mean values after 12 h of split-flow ventilation in 17 preterm infants weighing <2,000 g. Statistical analysis was performed using the T -test for matched pairs.

RESULTS

After switching from conventional ventilation to split-flow ventilation, the mean per-minute ventilation per kilogram of body weight decreased significantly from a mean value of 0.314+/-0.097 l/kg/min to 0.190+/-0.043 l/kg/min ( p <0.001), while the ventilation index decreased significantly from 28.47+/-7.48 to 16.10+/-4.13 ( p <0.001).

CONCLUSION

Split-flow ventilation significantly reduces apparatus dead space during ventilation in preterm infants. This leads to reduced ventilatory effort.