AIRWAY PRESSURE TRIGGERED VENTILATION FOR PRETERM NEONATES

The usefulness of airway pressure triggered ventilation for the preterm newborn has been assessed using a new patient triggered valveless ventilator, the SLE 2000 infant ventilator (SLE 2000). This ventilator performs well at fast rates with no inadvertent positive end expiratory pressure (PEEP) even at rates of 150 breaths per minute (bpm). The ventilator is triggered by a change in airway pressure equal to or exceeding 0.5 cmH2O. If the infant fails to achieve the change in airway pressure which will trigger the ventilator the infant is ventilated at the back-up rate which is predetermined in conventional mode prior to commencing PTV. Infants were ventilated for one hour on a conventional neonatal ventilator, then for one hour on the SLE 2000 in conventional mode without changing the ventilator settings and finally for one hour on the SLE 2000 in patient triggered mode. Arterial blood gases were checked at the end of each hour. During patient triggered ventilation (PTV) the peak pressure, inspiratory time and inspired oxygen concentration were the same as those used during conventional mode. Simultaneous recordings were made of flow, volume, ventilator and oesophageal pressure change, from this recording the trigger delay during PTV was calculated. The trigger delay, being the time lag from the start of spontaneous inspiration, indicated by the negative deflection in the oesophageal pressure trace, and the onset of the ventilator breath. Thirteen infants were included in the study. median gestational age 32 weeks (range 25-35) and birthweight 1640 g (range 838-3038). All were being ventilated for respiratory distress syndrome (RDS) and were 4 days of age. The median trigger delay was shown to be 80 msecs (range 40-100) and no phase shift was demonstrated between inspiration and inflation. The median paO2 following one hour on the conventional ventilator was 55 mmHg (range 47-92) and paCO2 was 36 mmHg (range 26-57). The arterial blood gases tended to improve, but not significantly, following one hour on the SLE ventilator in conventional mode, the median paO2 increased to 64 mmHg (range 42-94) and the paCO2 decreased to 32 mmHg (range 25-46). Following one hour of PTV both paO2 and paCO2 were significantly improved being a median of 68 mmHg (range 45-104), (p < 0.01) and 29 mmHg (range 18-40) (p < 0.01), respectively. We conclude airway pressure triggered PTV using the new valveless SLE 2000 infant ventilator is a useful form of neonatal ventilation.