Therapeutic Aerosols in Mechanically Ventilated Patients

Abstract

An aerosol is a suspension of solid or liquid particles in a gas. A nebulizer is a device that can convert a liquid into aerosol droplets suitable for patient inhalation. Aerosols have been used medicinally for thousands of years [1]. The inherent appeal of therapeutic aerosols is two fold: First, the delivery of pulmonary pharmaceuticals direct to the tracheo-bronchial and/or alveolar epithelium, and second, the rapid delivery of drugs to the systemic circulation. The latter, exploits the easily accessible, large absorptive surface area and minimal diffusion distance to the circulation that the respiratory tract provides, together with avoidance of first pass entero-hepatic metabolism. However, aerosols lack reliable and titratable dose delivery. This, coupled with the ready availability of intravenous access has largely relegated aerosolized therapy, in the mechanically ventilated intensive care unit (ICU) patient, to the empirical use of bronchodilators. In this chapter, we will examine whether newer aerosol producing technologies and recently published in vitro and in vivo testing allow us to reconsider the reliability of this method of drug delivery. We will also consider the efficacy of a range of aerosolized drugs that are commonly and less commonly used in mechanically ventilated ICU patients.