New generation neonatal high frequency ventilators: effect of oscillatory frequency and working principles on performance

Background: Several new generation neonatal ventilators that incorporate conventional as well as high frequency ventilation (HFOV) have appeared on the market. Most of them offer the possibility to use HFOV in a volume-targeted mode, despite absence of any preclinical data. With a bench test, we evaluated the performances of 4 new neonatal HFOV devices and compared them to the SensorMedics HFOV device.

Methods: Expiratory tidal volumes (V(T)) were measured for various ventilator settings and lung characteristics (ie, modifications of compliance and resistance of the system), to mimic several clinical conditions of pre-term and term infants.

Results: Increasing the frequency proportionally decreased the V(T) for all the ventilators, although the magnitude of the decrease was highly variable between ventilators. At 15 Hz and a pressure amplitude of 60 cm H2O, the delivered V(T) ranged from 3.5 to 5.9 mL between devices while simulating pre-term infant conditions and from 2.6 to 6.3 mL while simulating term infant conditions. Activating the volume-targeted mode in the 3 machines that offer this mode allowed the V(T) to remain constant over the range of frequencies and with changes of lung mechanical properties, for pre-term infant settings only while targeting a V(T) of 1 mL.

Conclusions: These new generation neonatal ventilators were able to deliver adequate V(T) under pre-term infant, but not term infant respiratory system conditions. The clinical relevance of these findings will need to be determined by further studies.