Administration of Beta-agonistic Drug Using Two Different Nebulizer Technologies: Effects on Lung Mechanics

The delivery of aerosols has a two fold appeal as it is distributed direct to the tracheo- bronchial tree and alveolar epithelium. The drug is then rapidly absorbed by the circulation avoiding the first pass entero-hepatic metabolic effect.

The systemic effects may be regarded as a side effect in the case were the primary therapeutic target is aimed at the bronchial tree as is the case with broncho-active drugs, such as β2-stimulants.

The ability of particles to remain suspended in a gas can be predicted from their size, shape and density, coupled with the density and viscosity of the gas. The properties of an aerosol is commonly expressed as the Mass Median Aerosol Diameter MMAD, a measure of the average particle size and the geometric standard deviation. It is calculated from the cumulative particle size curve1. The MMAD will give a reliable estimate of the likely deposition of the drug along the tracheo-bronchial tree. A particle size >5 will likely deposit in the upper airways, while particles with an MMAD of 2-5 is likely to deposit in the tracheo-bronchial tree2.

Jet nebulizers are the most commonly used devices for aerosol therapy. However, the MMAD generated by this device is unpredictable, often leading to the drug being deposited in the ventilator circuit or endotracheal tube3.

An alternative is the vibrating mesh nebulizer, which is based on a high frequency vibrating piezoelectric crystal. The crystal will vibrate a micron mesh at a very high frequency. A micro pump will deliver a small volume of liquid from a reservoir into the vibrating mesh resulting in a very precise aerosol generation3.