Inhaled aerosols: Emerging clinical methods

Abstract

Abstract The pattern of deposition of inhaled aerosols in the lungs of man in health and disease, in vivo, is reliant on multiple factors. The disease being targeted has a major influence on the eventual site of deposition. Obstructive lung disease alters the flow dynamics within the airways and restrictive lung diseases alters the ‘stiffness’ of the lungs and ability to inhale large volumes. There are multiple methods used to assess the fate of an inhaled aerosol within the lungs and the consequent clinical effect. Imaging allows visualization of inhaled aerosols via the use of labeling with radio-isotopes combined with imaging techniques such as planar scintigraphy, single photon emission computed tomography (SPECT) and positron emission tomography (PET). Computed tomography (CT), and magnetic resonance imaging (MRI) allow visualization of the structure of the lung and can also offer information of physiological dysfunction. Data from imaging can be related to physiological measurements of lung function and to clinical outcome. The combination of lung CT images with Computational Fluid and Particle Dynamics (CFPD) simulations has led to the development of personalized functional modeling of the airways to investigate disease in the small and large airways. All of these methods have advantages, disadvantages and limitations. None of these methods are able to directly visualize the small airways which is frequently the area of interest in lung disease. There are emerging methods of interest that may offer further data on the effects of inhaled therapeutic agents including novel MRI methods and use of micro-CT to investigate changes in small airway function. This chapter will summarize developments relating to inhaled aerosols and emerging clinical methods used to assess efficacy.