Assist control volume guarantee ventilation during surfactant administration

Abstract

Objective: To measure changes in ventilator parameters in preterm infants receiving surfactant during assist control volume guarantee (AC/VG) ventilation.

Methods: 22 preterm infants (up to 32 weeks' gestation) receiving surfactant for respiratory distress syndrome were enrolled in a prospective study of ventilator parameters during AC/VG ventilation at a tertiary neonatal intensive care unit. Ventilator pressures, flow and tidal volume waveforms were recorded from the Dräger Babylog 8000 plus in real time, and compared to pre-surfactant measurements.

Results: Following surfactant administration, 21 of 22 babies experienced completely obstructed endotracheal gas flow. Peak inflation pressure (PIP) increased by a median (IQR) of 8 (4-10) cm H2O, and took 30-60 min to return to baseline. Inspired oxygen concentration was reduced from a median (IQR) of 39% (26%-44%) to 26% (21%-30%) in the first 5 min. The set maximum PIP (Pmax) limited the delivered PIP such that most babies received tidal volumes less than the target value (V(Ttarget)) immediately following surfactant delivery. Four infants, in a subgroup of 11 infants where Pmax was set to less than 10 cm H2O above baseline PIP, were still receiving <90% of V(Ttarget) 20 min post surfactant.

Conclusions: When giving surfactant during AC/VG ventilation, complete obstruction is common. PIPs increased and remain elevated for 30-60 min. The Pmax setting may restrict tidal volume delivery.