Neonatal volume guarantee: effects of spontaneous breathing, triggered and untriggered inflations.

Abstract

Background: During volume guarantee ventilation (VG) the peak pressure (PIP) for each ventilator inflation is adjusted to ensure the expired tidal volume (VTe) is close to the set VTe. We observed differences in PIP between inflations triggered by the infant’s inspirations and untriggered inflations.

Aim: To investigate the effects of triggered and untriggered inflations on PIP and VTe.

Methods: Neonates were ventilated with the Drager Babylog 8000 using assist control (SIPPV) and VG modes. Continuous recordings of ventilator pressures and tidal volumes were made at 200 Hz for 10 minutes.

Results In 10 infants, 6540 inflations were analysed of which 62% were triggered. Triggered inflations had a significantly lower mean (SD) PIP than untriggered inflations: 12.9 (4.9) v 17.0 (3.3) cm H2O, (p<0.001). Despite this, there was no significant difference in the VTe of each type of inflation (103% and 101% of the set VTe respectively). When a triggered inflation was immediately preceded or followed by an untriggered inflation the PIP changed by about 5 cm H2O. Between adjacent inflations of the same type, the change in PIP was less than 3 cm H2O: for triggered inflations it was 0.11 (1.50) and 0.06 (1.53) cm H2O for untriggered inflations.

Conclusion: During volume guarantee ventilation with the Drager Babylog 8000 the PIP was 4 cm H2O lower during triggered inflations than untriggered inflations although the expired tidal volumes was similar.