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EVALUATION OF PROTOTYPE "NEONATAL"
CIRCUIT IN PRESSURE CONTROLLED VENTILATION
John Dickson, RRT, Robert
Chatburn RRT, FAARC and Timothy R. Myers BS, RRT. Rainbow Babies & Children?s
Hospital. Cleveland, OH.
Introduction. The goal of
mechanical ventilation is adequate gas exchange with minimal lung tissue damage
and minimal circulatory disturbance. Tidal volume (VT) during pressure
controlled modes depends on the balance between respiratory system and ventilator
circuit compliance (ie, compliance of tubing material plus compressibility of
gas). Traditionally, circuit manufacturers have produced three circuits (neonatal,
pediatric and adult). Fisher-Paykel has developed an "adult" ventilator circuit
(low compressible volume loss) that effectively delivers safe pediatric VT eliminating the need for a special pediatric circuit. Now Fisher-Paykel has
developed a prototype "neonatal" single-limb, heated-wire, ventilator circuit
for the neonatal market. This neonatal circuit is made of the same material
that the adult circuit. We hypothesized no significant difference in delivered
VT between the Fisher-Paykel and our standard Allegiance circuit
under simulated time-cycled, pressure limited ventilation conditions.
Methods: Circuit compliance
was measured by connecting 4 circuits of each brand to a pressure manometer
and injected calibrated volumes (30 mL). To test our hypothesis of a no significant
difference in delivered VT at similar set peak pressures, 5 circuits
of each brand were tested under simulated ventilation using an Infrasonics Test
Lung (C=1cmH20/mL) as our patient. An Infant Star and a Fisher-Paykel
humidifier served as our ventilator system. Randomly set PIPs (10 to 48 cmH2O
2 cmH2O increments) were tested with resulting exhaled volumes measured
by the Novametrix Como+ monitor. Mean difference in VT was compared
with a t-test.
Results: Pressure volume plots
yielded circuit compliances of 1.13 (± 0.03) cmH20/mL (Fisher-Paykel)
and 0.99 (± 0.01) cmH20/mL (Allegiance). Volume delivery was not
different between the two circuits with the exception of the two lowest levels
of pressure control (10 and 12 cmH20: p = 0.02). The figure below
shows mean ± SD:
Conclusion: The new prototype
neonatal circuit by Fisher-Paykel demonstrated comparable tidal volumes to our
standard Allegiance neonatal circuit. While the Fisher-Paykel circuit delivered
statistically significant higher tidal volumes at the two lowest levels of pressures
tested in this study, a 1mL difference is probably clinically irrelevant in
most neonates.
OF-02-102
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