THE EFFECT OF SPACER PLACEMENT ON ALBUTEROL DELIVERY IN A PEDIATRIC MECHANICAL VENTILATOR-LUNG MODEL.
Ralph A. Lugo, PharmD, Jim Keenan, BS, RRT, Keith Elkins, BS. University of Utah College of Pharmacy and Primary Children's Medical Center, Salt Lake City, Utah.
Background: Aerosolized albuterol is commonly administered by MDI and spacer to mechanically ventilated children in the PICU. Manufacturers recommend placing the spacer in-line in the inspiratory limb of the circuit. We hypothesized that drug delivery may be increased by placing the spacer between the endotracheal tube and the circuit wye. The objective of this study was to compare albuterol delivery between these two positions using two commonly used spacers, ACEÒ (DHD Healthcare) and AerochamberÒ MV (Monaghan Medical Corp.).
Methods: The model consisted of a Bird VIP ventilator in a volume mode to simulate a 15-kg child with moderate lung disease: VT 150 mL (10 mL/kg), PIP 45 cm H2O, rate 12, TI 0.75 sec, PEEP 4 cm H2O, FiO2 0.4, ventilator flow 11 L/min, and gas conditioned to 34° C. The circuit was attached to a 5-mm endotracheal tube (ETT) and a pediatric test lung (Vent AidÒ TTLÒ): compliance = 7.1 mL/cm H2O and resistance = 95 cm H2O/L/s. Spacers were rinsed and dried prior to the study. Spacers were placed either in the inspiratory limb immediately proximal to the wye according to the package insert or between the circuit wye and ETT. A Sims filter (Sims Portex) was placed between the ETT and test lung to collect aerosolized albuterol. Ten replicate experiments were performed for each condition. Filters were rinsed with 50 mL of 50% methanol solution and albuterol concentration was analyzed chromatographically by HPLC (99.1% accuracy and CV < 3.3%, n=9).
Results: Mean (SD) albuterol delivery is presented below.
Position of Spacer
Albuterol Delivery (%)
Between wye and ETT
Between wye and ETT
* p<0.001 compared to ACEÒ in inspiratory limb; ** p<0.001 compared to AerochamberÒ MV in inspiratory limb (ANOVA with Tukey post hoc all pairwise comparison)
CONCLUSION: Placement of the ACEÒ and AerochamberÒ MV spacers between the wye and ETT results in superior drug delivery as compared to placement in the inspiratory limb of the circuit. Placement between the wye and ETT is clinically more convenient than in the inspiratory limb as adapting a spacer with pediatric ventilator tubing can be difficult and sometimes impossible.