2002 OPEN FORUM Abstracts
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.