Background Automatic tube compensation (ATC) is designed to compensate for endotracheal tube (ETT) resistance and associated flow-dependent pressure decrease across the ETT. ATC has been shown to decrease the work of breathing and improve synchrony in adults. There are no data in neonates.
Objective To compare the relative performance of increasing levels of ATC with varying ETT sizes using neonatal lung models generated by an active servo lung.
Methods Lung models were created using an active breathing lung simulator (Active Servo Lung 5000, Ingmar Medical) with a sinusoidal flow pattern. The Evita XL ventilator (Dräger) provided CPAP (5 cm H2O) and ATC at 0, 50, 90, and 100% compensation levels for 2.5, 3.0, 3.5, and 4.0 ETT sizes. Each ETT size was tested with a different lung model reflecting differences in respiratory system mechanics in spontaneously breathing infants of varying weights. Tidal volume (VT), peak inspiratory (PIP), and mean airway (MAP) pressures were measured both at the proximal (PRE) and distal (POST) end of the ETT (NICO, Novametrix).
Results The pressure gradients across the ETTs under these simulated neonatal flow conditions were very small. Thus, increasing the levels of ATC plus CPAP of 5 cm H2O did not result in significant increase in PIP or MAP in our model.
Conclusions Because the actual pressure gradient across the ETTs under neonatal flow conditions is quite small, this ATC system does not generate appreciable additional inspiratory pressure.
These data were presented at the 2005 Pediatric Academic Societies' Annual Meeting.
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