New Generation Neonatal High Frequency Ventilators: Effect of Oscillatory Frequency and Working Principles on Performance

Abstract

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.