2002 Abstracts

Introduction: Deposition of aerosolized medications from an in-line small volume nebulizer (SVN) has been shown to be dependent on a number of factors including flowrate, nebulizer position in the circuit, and inspiratory to expiratory ratio (I:E) on a mechanical ventilator. In addition to these factors constant flow (bias flow) through the circuit also affects optimal delivery. We hypothesized that isolating medication delivery from ventilator circuit using an enhancement device (ED) can significantly improve delivery of aerosolized medication.

Setup: Our enhancement device consists of a one way reservoir loop attached at the wye of the ventilator circuit using a female to female connector. This loop consists of a one way valve into the nebulizer T-piece. This is followed by 150 ml corrugated tubing (1-inch diameter) which acts as a reservoir. This reservoir connects to a patient T-piece connector with a one-way valve out in the connection to the other end of the wye loop.

Methods: We used a Michigan lung model with two filters positioned 200cc?s (24inches) from the wye. The lung compliance was set at 30cm H2O. The model was ventilated sequentially with two volume ventilators, TBird AVS and Bear 1000tes. Bias Flow was set at 10 L/M. Each ventilator was set on A/C, RR 15, Vt 500 cc, FiO2 21%, PEEP +5 cmH2O at I:E ratios 1:3 and 1:6. Location of the nebulizer port on the inspiratory side of the ventilator circuit was varied between 50cc?s, 100cc?s, and 150cc?s prior to wye. At each location SVNs were administered with 3mls of .5mg/ml albuterol at 7L/M for 15 minutes and samples were collected. SVNs were then administered through the nebulizer port of the enhancement device and samples were collected. The samples (filters with absorbed medication) were removed from the circuit following each nebulization and dissolved in 8mls of 70% ethanol in a sterile container. The filters remained in ethanol for approximately 8 hours. A sample of 0.7mls from each container was then analyzed using a spectrophotometer at 278 nanometers. The optical densities of each sample were then plotted on a graph of known albuterol concentrations to convert the data to mg albuterol/ml. and results were compared.

Results:

Discussion: Our data suggest that the delivery of nebulized medications can be significantly increased on any ventilator settings by attaching the in-line small volume nebulizer to the enhancement device. We believe that use of this device would enhance the care of mechanically ventilated asthmatics, often requiring short inspiratory times and prolonged expiratory time.