Abstract

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

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 at a tertiary neonatal intensive care unit. Ventilator pressures, flow and tidal volume waveforms were recorded from the Dräger Babylog 8000plus in real time, and compared to pre-surfactant measurements.

Results: Following surfactant, 21 of 22 babies experienced completely obstructed endotracheal gas flow. Peak inflation pressure (PIP) increased by median (IQR) 8 (4-10) cm H2O, and took 30-60 minutes to return to baseline. Inspired oxygen concentration was reduced from median (IQR) 39 (26-44)% to 26 (21-30)% in the first five minutes.

The set maximum PIP (Pmax) limited the delivered PIP such that most babies received tidal volumes less than target (VTtarget) immediately following surfactant delivery. Four infants, in a subgroup of 11 infants where Pmax was set less than 10 cm H2O above baseline PIP, were still receiving <90% VTtarget 20 minutes post surfactant.

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