Respiratory death space and ventilation of newborn infants

Abstract

The effect of dead space reduction was studied in 10 VLBW infants (GA 26-31 wks, mean BW 1100 grms) on mechanical ventilation using a constant flow ventilator with a flow sensor device (Draeger Babylog 8000, Lubeck, Germany). Shortening of the endotracheal tube and removal of the flow sensor resulted in a calculated 50% reduction of dead space (-2.3 ml) and in a fall of tcpCO2 from (mean and range) 45 (40-49) to 35 (31-36) mmHG. This corresponds to a increase of alveolar ventilation of 22% as predicted by calculation of the dead space changes. Further attempts were made in reducing dead space ventilation by using endotracheal tubes conceived for jet ventilation, using the jet entry for the inspiratory side, or by introducing a separate continuous inspiratory flow to the tip of the endotracheal tube. Besides a routinely performed shortening of the ET tube this means of ventilation was used with success in two VLBW infants with desperate respiratory situations who both survived, in an older infant with high-grade tracheal stenosis to wean him from the respirator and in three neonates with congenital diaphragmatic hernia in conjunction with delayed operative repair who could be weaned from respiratory support 4, 13 and 20 days post surgery. We conclude that dead space reduction is a means to achieve gentle ventilation and to reduce lung damage from artificial ventilation.