Aerosol Bolus Dispersion and Aerosol-Derived Airway Morphometry: Assessment of Lung Pathology and Response to Therapy,Part 2

ABSTRACT

This review discusses the potential utility of two methods using inhaled aerosol to detect and diagnose lung disease. Part 1, published earlier,⁽¹⁾ focused upon aerosol bolus dispersion, which measures convective gas mixing. Here, Part 2 focuses upon aerosol-derived airway morphometry (ADAM), which assesses the diameters of airways and acini. This method is discussed in terms of its validity, ability to detect known interventions and diseases, and reproducibility (administering and performing this procedure were already discussed⁽¹⁾. With ADAM, airway and acinar diameters are expressed in terms of the effective airway diameter (EAD), which can be measured as a function of volumetric depth in the lungs. Evidence that ADAM is valid is provided by studies showing EAD agrees well with morphometric indices of airway and acinar size, especially once the distribution of aerosol is accounted for, and changes appropriately in response to known interventions and several diseases. Of particular note is the ability of ADAM to detect and quantify emphysema. One limitation of using ADAM to compare airway dimensions among people is that EADs in this region are sensitive to variability in airway volume, which can confound these comparisons. In contrast, EADs measured in the peripheral lung are relatively insensitive to variations in airway volume, thus acinar EADs can be readily compared. Other attractive features of ADAM are that it is simple to administer, can be successfully performed by patients, and is reproducible. Thus, ADAM is a promising method to characterize the dimensions of peripheral lung structures; it may be particularly useful to diagnose emphysema and to follow this disease's progression and response to treatment