1724 PENETRATION OF THERAPEUTIC AEROSOLS (TA) THROUGH ENDOTRACHEAL TUBES (ETT)

Abstract

Because of observations of occasional toxicity from TA in intubated patients, we examined the site of deposition of TA delivered into 3.0, 6.0, and 9.0mm endotracheal tubes (ETT) using a constant flow in vitro model and 0.1% fluorescein as a tracer. A typical nebulizer (N) was used (aerodynamic massmedian diameter of 4.1) and a range of clinically relevant Inspiratory flow rates were studied. The N was connected to the ETT through a “T” piece and a 90 degree elbow. ETT ws bent 90° with a radius of curvature of 5.25 cm. TA exiting the ETT was collected in 80 L polyethylene bags. Because preliminary experiments showed that much of the TA which originally deposited the ETT, ran to the end of the ETT and dripped into the collection bag, appropriately sized plexiglass models of the trachea, and mainstem bronchi (MB), were constructed and placed on the end of each ETT to collect this drippage. Results, expressed as percent of inspired trace in each location, follow: Penetration of aerosol beyond the mainstem bronchi is decreased with increasing flow rate and decreasing ETT diameter. The study ws repeated with an alternative nebulizer delivering TA with an aerodynamic mass median diameter of .54. Aerosol penetration beyond the MB increased dramatically (to a range of 78-98%). Thus, a significant percentage of the TA delivered into the ETI during inspiration by usual nebulizers is deposited as a liquid bolus poured into the airway. This problem is nearly eliminated when a smaller particle size aerosol is used.